diff options
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/Makefile | 7 | ||||
| -rw-r--r-- | kernel/rcu/rcu.h | 146 | ||||
| -rw-r--r-- | kernel/rcu/rcutorture.c | 1861 | ||||
| -rw-r--r-- | kernel/rcu/srcu.c | 676 | ||||
| -rw-r--r-- | kernel/rcu/tiny.c | 288 | ||||
| -rw-r--r-- | kernel/rcu/tiny_plugin.h | 173 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 4136 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 620 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 3090 | ||||
| -rw-r--r-- | kernel/rcu/tree_trace.c | 505 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 831 |
11 files changed, 12333 insertions, 0 deletions
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile new file mode 100644 index 000000000..50a808424 --- /dev/null +++ b/kernel/rcu/Makefile @@ -0,0 +1,7 @@ +obj-y += update.o +obj-$(CONFIG_SRCU) += srcu.o +obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o +obj-$(CONFIG_TREE_RCU) += tree.o +obj-$(CONFIG_PREEMPT_RCU) += tree.o +obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o +obj-$(CONFIG_TINY_RCU) += tiny.o diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h new file mode 100644 index 000000000..80adef7d4 --- /dev/null +++ b/kernel/rcu/rcu.h @@ -0,0 +1,146 @@ +/* + * Read-Copy Update definitions shared among RCU implementations. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2011 + * + * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#ifndef __LINUX_RCU_H +#define __LINUX_RCU_H + +#include <trace/events/rcu.h> +#ifdef CONFIG_RCU_TRACE +#define RCU_TRACE(stmt) stmt +#else /* #ifdef CONFIG_RCU_TRACE */ +#define RCU_TRACE(stmt) +#endif /* #else #ifdef CONFIG_RCU_TRACE */ + +/* + * Process-level increment to ->dynticks_nesting field. This allows for + * architectures that use half-interrupts and half-exceptions from + * process context. + * + * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH + * that counts the number of process-based reasons why RCU cannot + * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE + * is the value used to increment or decrement this field. + * + * The rest of the bits could in principle be used to count interrupts, + * but this would mean that a negative-one value in the interrupt + * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field. + * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK + * that is set to DYNTICK_TASK_FLAG upon initial exit from idle. + * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon + * initial exit from idle. + */ +#define DYNTICK_TASK_NEST_WIDTH 7 +#define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1) +#define DYNTICK_TASK_NEST_MASK (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1) +#define DYNTICK_TASK_FLAG ((DYNTICK_TASK_NEST_VALUE / 8) * 2) +#define DYNTICK_TASK_MASK ((DYNTICK_TASK_NEST_VALUE / 8) * 3) +#define DYNTICK_TASK_EXIT_IDLE (DYNTICK_TASK_NEST_VALUE + \ + DYNTICK_TASK_FLAG) + +/* + * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally + * by call_rcu() and rcu callback execution, and are therefore not part of the + * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. + */ + +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +# define STATE_RCU_HEAD_READY 0 +# define STATE_RCU_HEAD_QUEUED 1 + +extern struct debug_obj_descr rcuhead_debug_descr; + +static inline int debug_rcu_head_queue(struct rcu_head *head) +{ + int r1; + + r1 = debug_object_activate(head, &rcuhead_debug_descr); + debug_object_active_state(head, &rcuhead_debug_descr, + STATE_RCU_HEAD_READY, + STATE_RCU_HEAD_QUEUED); + return r1; +} + +static inline void debug_rcu_head_unqueue(struct rcu_head *head) +{ + debug_object_active_state(head, &rcuhead_debug_descr, + STATE_RCU_HEAD_QUEUED, + STATE_RCU_HEAD_READY); + debug_object_deactivate(head, &rcuhead_debug_descr); +} +#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +static inline int debug_rcu_head_queue(struct rcu_head *head) +{ + return 0; +} + +static inline void debug_rcu_head_unqueue(struct rcu_head *head) +{ +} +#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + +void kfree(const void *); + +/* + * Reclaim the specified callback, either by invoking it (non-lazy case) + * or freeing it directly (lazy case). Return true if lazy, false otherwise. + */ +static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head) +{ + unsigned long offset = (unsigned long)head->func; + + rcu_lock_acquire(&rcu_callback_map); + if (__is_kfree_rcu_offset(offset)) { + RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset)); + kfree((void *)head - offset); + rcu_lock_release(&rcu_callback_map); + return true; + } else { + RCU_TRACE(trace_rcu_invoke_callback(rn, head)); + head->func(head); + rcu_lock_release(&rcu_callback_map); + return false; + } +} + +#ifdef CONFIG_RCU_STALL_COMMON + +extern int rcu_cpu_stall_suppress; +int rcu_jiffies_till_stall_check(void); + +#endif /* #ifdef CONFIG_RCU_STALL_COMMON */ + +/* + * Strings used in tracepoints need to be exported via the + * tracing system such that tools like perf and trace-cmd can + * translate the string address pointers to actual text. + */ +#define TPS(x) tracepoint_string(x) + +void rcu_early_boot_tests(void); + +/* + * This function really isn't for public consumption, but RCU is special in + * that context switches can allow the state machine to make progress. + */ +extern void resched_cpu(int cpu); + +#endif /* __LINUX_RCU_H */ diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c new file mode 100644 index 000000000..8dbe27611 --- /dev/null +++ b/kernel/rcu/rcutorture.c @@ -0,0 +1,1861 @@ +/* + * Read-Copy Update module-based torture test facility + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright (C) IBM Corporation, 2005, 2006 + * + * Authors: Paul E. McKenney <paulmck@us.ibm.com> + * Josh Triplett <josh@joshtriplett.org> + * + * See also: Documentation/RCU/torture.txt + */ +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/kthread.h> +#include <linux/err.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/rcupdate.h> +#include <linux/interrupt.h> +#include <linux/sched.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/completion.h> +#include <linux/moduleparam.h> +#include <linux/percpu.h> +#include <linux/notifier.h> +#include <linux/reboot.h> +#include <linux/freezer.h> +#include <linux/cpu.h> +#include <linux/delay.h> +#include <linux/stat.h> +#include <linux/srcu.h> +#include <linux/slab.h> +#include <linux/trace_clock.h> +#include <asm/byteorder.h> +#include <linux/torture.h> +#include <linux/vmalloc.h> + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@joshtriplett.org>"); + + +torture_param(int, cbflood_inter_holdoff, HZ, + "Holdoff between floods (jiffies)"); +torture_param(int, cbflood_intra_holdoff, 1, + "Holdoff between bursts (jiffies)"); +torture_param(int, cbflood_n_burst, 3, "# bursts in flood, zero to disable"); +torture_param(int, cbflood_n_per_burst, 20000, + "# callbacks per burst in flood"); +torture_param(int, fqs_duration, 0, + "Duration of fqs bursts (us), 0 to disable"); +torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)"); +torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)"); +torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives"); +torture_param(bool, gp_exp, false, "Use expedited GP wait primitives"); +torture_param(bool, gp_normal, false, + "Use normal (non-expedited) GP wait primitives"); +torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives"); +torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers"); +torture_param(int, n_barrier_cbs, 0, + "# of callbacks/kthreads for barrier testing"); +torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads"); +torture_param(int, nreaders, -1, "Number of RCU reader threads"); +torture_param(int, object_debug, 0, + "Enable debug-object double call_rcu() testing"); +torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)"); +torture_param(int, onoff_interval, 0, + "Time between CPU hotplugs (s), 0=disable"); +torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles"); +torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable."); +torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable."); +torture_param(int, stall_cpu_holdoff, 10, + "Time to wait before starting stall (s)."); +torture_param(int, stat_interval, 60, + "Number of seconds between stats printk()s"); +torture_param(int, stutter, 5, "Number of seconds to run/halt test"); +torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes."); +torture_param(int, test_boost_duration, 4, + "Duration of each boost test, seconds."); +torture_param(int, test_boost_interval, 7, + "Interval between boost tests, seconds."); +torture_param(bool, test_no_idle_hz, true, + "Test support for tickless idle CPUs"); +torture_param(bool, verbose, true, + "Enable verbose debugging printk()s"); + +static char *torture_type = "rcu"; +module_param(torture_type, charp, 0444); +MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, ...)"); + +static int nrealreaders; +static int ncbflooders; +static struct task_struct *writer_task; +static struct task_struct **fakewriter_tasks; +static struct task_struct **reader_tasks; +static struct task_struct *stats_task; +static struct task_struct **cbflood_task; +static struct task_struct *fqs_task; +static struct task_struct *boost_tasks[NR_CPUS]; +static struct task_struct *stall_task; +static struct task_struct **barrier_cbs_tasks; +static struct task_struct *barrier_task; + +#define RCU_TORTURE_PIPE_LEN 10 + +struct rcu_torture { + struct rcu_head rtort_rcu; + int rtort_pipe_count; + struct list_head rtort_free; + int rtort_mbtest; +}; + +static LIST_HEAD(rcu_torture_freelist); +static struct rcu_torture __rcu *rcu_torture_current; +static unsigned long rcu_torture_current_version; +static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN]; +static DEFINE_SPINLOCK(rcu_torture_lock); +static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], + rcu_torture_count) = { 0 }; +static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], + rcu_torture_batch) = { 0 }; +static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1]; +static atomic_t n_rcu_torture_alloc; +static atomic_t n_rcu_torture_alloc_fail; +static atomic_t n_rcu_torture_free; +static atomic_t n_rcu_torture_mberror; +static atomic_t n_rcu_torture_error; +static long n_rcu_torture_barrier_error; +static long n_rcu_torture_boost_ktrerror; +static long n_rcu_torture_boost_rterror; +static long n_rcu_torture_boost_failure; +static long n_rcu_torture_boosts; +static long n_rcu_torture_timers; +static long n_barrier_attempts; +static long n_barrier_successes; +static atomic_long_t n_cbfloods; +static struct list_head rcu_torture_removed; + +static int rcu_torture_writer_state; +#define RTWS_FIXED_DELAY 0 +#define RTWS_DELAY 1 +#define RTWS_REPLACE 2 +#define RTWS_DEF_FREE 3 +#define RTWS_EXP_SYNC 4 +#define RTWS_COND_GET 5 +#define RTWS_COND_SYNC 6 +#define RTWS_SYNC 7 +#define RTWS_STUTTER 8 +#define RTWS_STOPPING 9 + +#if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE) +#define RCUTORTURE_RUNNABLE_INIT 1 +#else +#define RCUTORTURE_RUNNABLE_INIT 0 +#endif +static int torture_runnable = RCUTORTURE_RUNNABLE_INIT; +module_param(torture_runnable, int, 0444); +MODULE_PARM_DESC(torture_runnable, "Start rcutorture at boot"); + +#if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) +#define rcu_can_boost() 1 +#else /* #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */ +#define rcu_can_boost() 0 +#endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */ + +#ifdef CONFIG_RCU_TRACE +static u64 notrace rcu_trace_clock_local(void) +{ + u64 ts = trace_clock_local(); + unsigned long __maybe_unused ts_rem = do_div(ts, NSEC_PER_USEC); + return ts; +} +#else /* #ifdef CONFIG_RCU_TRACE */ +static u64 notrace rcu_trace_clock_local(void) +{ + return 0ULL; +} +#endif /* #else #ifdef CONFIG_RCU_TRACE */ + +static unsigned long boost_starttime; /* jiffies of next boost test start. */ +static DEFINE_MUTEX(boost_mutex); /* protect setting boost_starttime */ + /* and boost task create/destroy. */ +static atomic_t barrier_cbs_count; /* Barrier callbacks registered. */ +static bool barrier_phase; /* Test phase. */ +static atomic_t barrier_cbs_invoked; /* Barrier callbacks invoked. */ +static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */ +static DECLARE_WAIT_QUEUE_HEAD(barrier_wq); + +/* + * Allocate an element from the rcu_tortures pool. + */ +static struct rcu_torture * +rcu_torture_alloc(void) +{ + struct list_head *p; + + spin_lock_bh(&rcu_torture_lock); + if (list_empty(&rcu_torture_freelist)) { + atomic_inc(&n_rcu_torture_alloc_fail); + spin_unlock_bh(&rcu_torture_lock); + return NULL; + } + atomic_inc(&n_rcu_torture_alloc); + p = rcu_torture_freelist.next; + list_del_init(p); + spin_unlock_bh(&rcu_torture_lock); + return container_of(p, struct rcu_torture, rtort_free); +} + +/* + * Free an element to the rcu_tortures pool. + */ +static void +rcu_torture_free(struct rcu_torture *p) +{ + atomic_inc(&n_rcu_torture_free); + spin_lock_bh(&rcu_torture_lock); + list_add_tail(&p->rtort_free, &rcu_torture_freelist); + spin_unlock_bh(&rcu_torture_lock); +} + +/* + * Operations vector for selecting different types of tests. + */ + +struct rcu_torture_ops { + int ttype; + void (*init)(void); + int (*readlock)(void); + void (*read_delay)(struct torture_random_state *rrsp); + void (*readunlock)(int idx); + unsigned long (*started)(void); + unsigned long (*completed)(void); + void (*deferred_free)(struct rcu_torture *p); + void (*sync)(void); + void (*exp_sync)(void); + unsigned long (*get_state)(void); + void (*cond_sync)(unsigned long oldstate); + void (*call)(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); + void (*cb_barrier)(void); + void (*fqs)(void); + void (*stats)(void); + int irq_capable; + int can_boost; + const char *name; +}; + +static struct rcu_torture_ops *cur_ops; + +/* + * Definitions for rcu torture testing. + */ + +static int rcu_torture_read_lock(void) __acquires(RCU) +{ + rcu_read_lock(); + return 0; +} + +static void rcu_read_delay(struct torture_random_state *rrsp) +{ + const unsigned long shortdelay_us = 200; + const unsigned long longdelay_ms = 50; + + /* We want a short delay sometimes to make a reader delay the grace + * period, and we want a long delay occasionally to trigger + * force_quiescent_state. */ + + if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) + mdelay(longdelay_ms); + if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) + udelay(shortdelay_us); +#ifdef CONFIG_PREEMPT + if (!preempt_count() && + !(torture_random(rrsp) % (nrealreaders * 20000))) + preempt_schedule(); /* No QS if preempt_disable() in effect */ +#endif +} + +static void rcu_torture_read_unlock(int idx) __releases(RCU) +{ + rcu_read_unlock(); +} + +/* + * Update callback in the pipe. This should be invoked after a grace period. + */ +static bool +rcu_torture_pipe_update_one(struct rcu_torture *rp) +{ + int i; + + i = rp->rtort_pipe_count; + if (i > RCU_TORTURE_PIPE_LEN) + i = RCU_TORTURE_PIPE_LEN; + atomic_inc(&rcu_torture_wcount[i]); + if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) { + rp->rtort_mbtest = 0; + return true; + } + return false; +} + +/* + * Update all callbacks in the pipe. Suitable for synchronous grace-period + * primitives. + */ +static void +rcu_torture_pipe_update(struct rcu_torture *old_rp) +{ + struct rcu_torture *rp; + struct rcu_torture *rp1; + + if (old_rp) + list_add(&old_rp->rtort_free, &rcu_torture_removed); + list_for_each_entry_safe(rp, rp1, &rcu_torture_removed, rtort_free) { + if (rcu_torture_pipe_update_one(rp)) { + list_del(&rp->rtort_free); + rcu_torture_free(rp); + } + } +} + +static void +rcu_torture_cb(struct rcu_head *p) +{ + struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu); + + if (torture_must_stop_irq()) { + /* Test is ending, just drop callbacks on the floor. */ + /* The next initialization will pick up the pieces. */ + return; + } + if (rcu_torture_pipe_update_one(rp)) + rcu_torture_free(rp); + else + cur_ops->deferred_free(rp); +} + +static unsigned long rcu_no_completed(void) +{ + return 0; +} + +static void rcu_torture_deferred_free(struct rcu_torture *p) +{ + call_rcu(&p->rtort_rcu, rcu_torture_cb); +} + +static void rcu_sync_torture_init(void) +{ + INIT_LIST_HEAD(&rcu_torture_removed); +} + +static struct rcu_torture_ops rcu_ops = { + .ttype = RCU_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = rcu_torture_read_lock, + .read_delay = rcu_read_delay, + .readunlock = rcu_torture_read_unlock, + .started = rcu_batches_started, + .completed = rcu_batches_completed, + .deferred_free = rcu_torture_deferred_free, + .sync = synchronize_rcu, + .exp_sync = synchronize_rcu_expedited, + .get_state = get_state_synchronize_rcu, + .cond_sync = cond_synchronize_rcu, + .call = call_rcu, + .cb_barrier = rcu_barrier, + .fqs = rcu_force_quiescent_state, + .stats = NULL, + .irq_capable = 1, + .can_boost = rcu_can_boost(), + .name = "rcu" +}; + +/* + * Definitions for rcu_bh torture testing. + */ + +static int rcu_bh_torture_read_lock(void) __acquires(RCU_BH) +{ + rcu_read_lock_bh(); + return 0; +} + +static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH) +{ + rcu_read_unlock_bh(); +} + +static void rcu_bh_torture_deferred_free(struct rcu_torture *p) +{ + call_rcu_bh(&p->rtort_rcu, rcu_torture_cb); +} + +static struct rcu_torture_ops rcu_bh_ops = { + .ttype = RCU_BH_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = rcu_bh_torture_read_lock, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = rcu_bh_torture_read_unlock, + .started = rcu_batches_started_bh, + .completed = rcu_batches_completed_bh, + .deferred_free = rcu_bh_torture_deferred_free, + .sync = synchronize_rcu_bh, + .exp_sync = synchronize_rcu_bh_expedited, + .call = call_rcu_bh, + .cb_barrier = rcu_barrier_bh, + .fqs = rcu_bh_force_quiescent_state, + .stats = NULL, + .irq_capable = 1, + .name = "rcu_bh" +}; + +/* + * Don't even think about trying any of these in real life!!! + * The names includes "busted", and they really means it! + * The only purpose of these functions is to provide a buggy RCU + * implementation to make sure that rcutorture correctly emits + * buggy-RCU error messages. + */ +static void rcu_busted_torture_deferred_free(struct rcu_torture *p) +{ + /* This is a deliberate bug for testing purposes only! */ + rcu_torture_cb(&p->rtort_rcu); +} + +static void synchronize_rcu_busted(void) +{ + /* This is a deliberate bug for testing purposes only! */ +} + +static void +call_rcu_busted(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + /* This is a deliberate bug for testing purposes only! */ + func(head); +} + +static struct rcu_torture_ops rcu_busted_ops = { + .ttype = INVALID_RCU_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = rcu_torture_read_lock, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = rcu_torture_read_unlock, + .started = rcu_no_completed, + .completed = rcu_no_completed, + .deferred_free = rcu_busted_torture_deferred_free, + .sync = synchronize_rcu_busted, + .exp_sync = synchronize_rcu_busted, + .call = call_rcu_busted, + .cb_barrier = NULL, + .fqs = NULL, + .stats = NULL, + .irq_capable = 1, + .name = "rcu_busted" +}; + +/* + * Definitions for srcu torture testing. + */ + +DEFINE_STATIC_SRCU(srcu_ctl); + +static int srcu_torture_read_lock(void) __acquires(&srcu_ctl) +{ + return srcu_read_lock(&srcu_ctl); +} + +static void srcu_read_delay(struct torture_random_state *rrsp) +{ + long delay; + const long uspertick = 1000000 / HZ; + const long longdelay = 10; + + /* We want there to be long-running readers, but not all the time. */ + + delay = torture_random(rrsp) % + (nrealreaders * 2 * longdelay * uspertick); + if (!delay) + schedule_timeout_interruptible(longdelay); + else + rcu_read_delay(rrsp); +} + +static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl) +{ + srcu_read_unlock(&srcu_ctl, idx); +} + +static unsigned long srcu_torture_completed(void) +{ + return srcu_batches_completed(&srcu_ctl); +} + +static void srcu_torture_deferred_free(struct rcu_torture *rp) +{ + call_srcu(&srcu_ctl, &rp->rtort_rcu, rcu_torture_cb); +} + +static void srcu_torture_synchronize(void) +{ + synchronize_srcu(&srcu_ctl); +} + +static void srcu_torture_call(struct rcu_head *head, + void (*func)(struct rcu_head *head)) +{ + call_srcu(&srcu_ctl, head, func); +} + +static void srcu_torture_barrier(void) +{ + srcu_barrier(&srcu_ctl); +} + +static void srcu_torture_stats(void) +{ + int cpu; + int idx = srcu_ctl.completed & 0x1; + + pr_alert("%s%s per-CPU(idx=%d):", + torture_type, TORTURE_FLAG, idx); + for_each_possible_cpu(cpu) { + long c0, c1; + + c0 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx]; + c1 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]; + pr_cont(" %d(%ld,%ld)", cpu, c0, c1); + } + pr_cont("\n"); +} + +static void srcu_torture_synchronize_expedited(void) +{ + synchronize_srcu_expedited(&srcu_ctl); +} + +static struct rcu_torture_ops srcu_ops = { + .ttype = SRCU_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = srcu_torture_read_lock, + .read_delay = srcu_read_delay, + .readunlock = srcu_torture_read_unlock, + .started = NULL, + .completed = srcu_torture_completed, + .deferred_free = srcu_torture_deferred_free, + .sync = srcu_torture_synchronize, + .exp_sync = srcu_torture_synchronize_expedited, + .call = srcu_torture_call, + .cb_barrier = srcu_torture_barrier, + .stats = srcu_torture_stats, + .name = "srcu" +}; + +/* + * Definitions for sched torture testing. + */ + +static int sched_torture_read_lock(void) +{ + preempt_disable(); + return 0; +} + +static void sched_torture_read_unlock(int idx) +{ + preempt_enable(); +} + +static void rcu_sched_torture_deferred_free(struct rcu_torture *p) +{ + call_rcu_sched(&p->rtort_rcu, rcu_torture_cb); +} + +static struct rcu_torture_ops sched_ops = { + .ttype = RCU_SCHED_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = sched_torture_read_lock, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = sched_torture_read_unlock, + .started = rcu_batches_started_sched, + .completed = rcu_batches_completed_sched, + .deferred_free = rcu_sched_torture_deferred_free, + .sync = synchronize_sched, + .exp_sync = synchronize_sched_expedited, + .call = call_rcu_sched, + .cb_barrier = rcu_barrier_sched, + .fqs = rcu_sched_force_quiescent_state, + .stats = NULL, + .irq_capable = 1, + .name = "sched" +}; + +#ifdef CONFIG_TASKS_RCU + +/* + * Definitions for RCU-tasks torture testing. + */ + +static int tasks_torture_read_lock(void) +{ + return 0; +} + +static void tasks_torture_read_unlock(int idx) +{ +} + +static void rcu_tasks_torture_deferred_free(struct rcu_torture *p) +{ + call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb); +} + +static struct rcu_torture_ops tasks_ops = { + .ttype = RCU_TASKS_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = tasks_torture_read_lock, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = tasks_torture_read_unlock, + .started = rcu_no_completed, + .completed = rcu_no_completed, + .deferred_free = rcu_tasks_torture_deferred_free, + .sync = synchronize_rcu_tasks, + .exp_sync = synchronize_rcu_tasks, + .call = call_rcu_tasks, + .cb_barrier = rcu_barrier_tasks, + .fqs = NULL, + .stats = NULL, + .irq_capable = 1, + .name = "tasks" +}; + +#define RCUTORTURE_TASKS_OPS &tasks_ops, + +#else /* #ifdef CONFIG_TASKS_RCU */ + +#define RCUTORTURE_TASKS_OPS + +#endif /* #else #ifdef CONFIG_TASKS_RCU */ + +/* + * RCU torture priority-boost testing. Runs one real-time thread per + * CPU for moderate bursts, repeatedly registering RCU callbacks and + * spinning waiting for them to be invoked. If a given callback takes + * too long to be invoked, we assume that priority inversion has occurred. + */ + +struct rcu_boost_inflight { + struct rcu_head rcu; + int inflight; +}; + +static void rcu_torture_boost_cb(struct rcu_head *head) +{ + struct rcu_boost_inflight *rbip = + container_of(head, struct rcu_boost_inflight, rcu); + + smp_mb(); /* Ensure RCU-core accesses precede clearing ->inflight */ + rbip->inflight = 0; +} + +static int rcu_torture_boost(void *arg) +{ + unsigned long call_rcu_time; + unsigned long endtime; + unsigned long oldstarttime; + struct rcu_boost_inflight rbi = { .inflight = 0 }; + struct sched_param sp; + + VERBOSE_TOROUT_STRING("rcu_torture_boost started"); + + /* Set real-time priority. */ + sp.sched_priority = 1; + if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) { + VERBOSE_TOROUT_STRING("rcu_torture_boost RT prio failed!"); + n_rcu_torture_boost_rterror++; + } + + init_rcu_head_on_stack(&rbi.rcu); + /* Each pass through the following loop does one boost-test cycle. */ + do { + /* Wait for the next test interval. */ + oldstarttime = boost_starttime; + while (ULONG_CMP_LT(jiffies, oldstarttime)) { + schedule_timeout_interruptible(oldstarttime - jiffies); + stutter_wait("rcu_torture_boost"); + if (torture_must_stop()) + goto checkwait; + } + + /* Do one boost-test interval. */ + endtime = oldstarttime + test_boost_duration * HZ; + call_rcu_time = jiffies; + while (ULONG_CMP_LT(jiffies, endtime)) { + /* If we don't have a callback in flight, post one. */ + if (!rbi.inflight) { + smp_mb(); /* RCU core before ->inflight = 1. */ + rbi.inflight = 1; + call_rcu(&rbi.rcu, rcu_torture_boost_cb); + if (jiffies - call_rcu_time > + test_boost_duration * HZ - HZ / 2) { + VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed"); + n_rcu_torture_boost_failure++; + } + call_rcu_time = jiffies; + } + cond_resched_rcu_qs(); + stutter_wait("rcu_torture_boost"); + if (torture_must_stop()) + goto checkwait; + } + + /* + * Set the start time of the next test interval. + * Yes, this is vulnerable to long delays, but such + * delays simply cause a false negative for the next + * interval. Besides, we are running at RT priority, + * so delays should be relatively rare. + */ + while (oldstarttime == boost_starttime && + !kthread_should_stop()) { + if (mutex_trylock(&boost_mutex)) { + boost_starttime = jiffies + + test_boost_interval * HZ; + n_rcu_torture_boosts++; + mutex_unlock(&boost_mutex); + break; + } + schedule_timeout_uninterruptible(1); + } + + /* Go do the stutter. */ +checkwait: stutter_wait("rcu_torture_boost"); + } while (!torture_must_stop()); + + /* Clean up and exit. */ + while (!kthread_should_stop() || rbi.inflight) { + torture_shutdown_absorb("rcu_torture_boost"); + schedule_timeout_uninterruptible(1); + } + smp_mb(); /* order accesses to ->inflight before stack-frame death. */ + destroy_rcu_head_on_stack(&rbi.rcu); + torture_kthread_stopping("rcu_torture_boost"); + return 0; +} + +static void rcu_torture_cbflood_cb(struct rcu_head *rhp) +{ +} + +/* + * RCU torture callback-flood kthread. Repeatedly induces bursts of calls + * to call_rcu() or analogous, increasing the probability of occurrence + * of callback-overflow corner cases. + */ +static int +rcu_torture_cbflood(void *arg) +{ + int err = 1; + int i; + int j; + struct rcu_head *rhp; + + if (cbflood_n_per_burst > 0 && + cbflood_inter_holdoff > 0 && + cbflood_intra_holdoff > 0 && + cur_ops->call && + cur_ops->cb_barrier) { + rhp = vmalloc(sizeof(*rhp) * + cbflood_n_burst * cbflood_n_per_burst); + err = !rhp; + } + if (err) { + VERBOSE_TOROUT_STRING("rcu_torture_cbflood disabled: Bad args or OOM"); + while (!torture_must_stop()) + schedule_timeout_interruptible(HZ); + return 0; + } + VERBOSE_TOROUT_STRING("rcu_torture_cbflood task started"); + do { + schedule_timeout_interruptible(cbflood_inter_holdoff); + atomic_long_inc(&n_cbfloods); + WARN_ON(signal_pending(current)); + for (i = 0; i < cbflood_n_burst; i++) { + for (j = 0; j < cbflood_n_per_burst; j++) { + cur_ops->call(&rhp[i * cbflood_n_per_burst + j], + rcu_torture_cbflood_cb); + } + schedule_timeout_interruptible(cbflood_intra_holdoff); + WARN_ON(signal_pending(current)); + } + cur_ops->cb_barrier(); + stutter_wait("rcu_torture_cbflood"); + } while (!torture_must_stop()); + vfree(rhp); + torture_kthread_stopping("rcu_torture_cbflood"); + return 0; +} + +/* + * RCU torture force-quiescent-state kthread. Repeatedly induces + * bursts of calls to force_quiescent_state(), increasing the probability + * of occurrence of some important types of race conditions. + */ +static int +rcu_torture_fqs(void *arg) +{ + unsigned long fqs_resume_time; + int fqs_burst_remaining; + + VERBOSE_TOROUT_STRING("rcu_torture_fqs task started"); + do { + fqs_resume_time = jiffies + fqs_stutter * HZ; + while (ULONG_CMP_LT(jiffies, fqs_resume_time) && + !kthread_should_stop()) { + schedule_timeout_interruptible(1); + } + fqs_burst_remaining = fqs_duration; + while (fqs_burst_remaining > 0 && + !kthread_should_stop()) { + cur_ops->fqs(); + udelay(fqs_holdoff); + fqs_burst_remaining -= fqs_holdoff; + } + stutter_wait("rcu_torture_fqs"); + } while (!torture_must_stop()); + torture_kthread_stopping("rcu_torture_fqs"); + return 0; +} + +/* + * RCU torture writer kthread. Repeatedly substitutes a new structure + * for that pointed to by rcu_torture_current, freeing the old structure + * after a series of grace periods (the "pipeline"). + */ +static int +rcu_torture_writer(void *arg) +{ + bool can_expedite = !rcu_gp_is_expedited(); + int expediting = 0; + unsigned long gp_snap; + bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal; + bool gp_sync1 = gp_sync; + int i; + struct rcu_torture *rp; + struct rcu_torture *old_rp; + static DEFINE_TORTURE_RANDOM(rand); + int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC, + RTWS_COND_GET, RTWS_SYNC }; + int nsynctypes = 0; + + VERBOSE_TOROUT_STRING("rcu_torture_writer task started"); + pr_alert("%s" TORTURE_FLAG + " Grace periods expedited from boot/sysfs for %s,\n", + torture_type, cur_ops->name); + pr_alert("%s" TORTURE_FLAG + " Testing of dynamic grace-period expediting diabled.\n", + torture_type); + + /* Initialize synctype[] array. If none set, take default. */ + if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync1) + gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true; + if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync) + synctype[nsynctypes++] = RTWS_COND_GET; + else if (gp_cond && (!cur_ops->get_state || !cur_ops->cond_sync)) + pr_alert("rcu_torture_writer: gp_cond without primitives.\n"); + if (gp_exp1 && cur_ops->exp_sync) + synctype[nsynctypes++] = RTWS_EXP_SYNC; + else if (gp_exp && !cur_ops->exp_sync) + pr_alert("rcu_torture_writer: gp_exp without primitives.\n"); + if (gp_normal1 && cur_ops->deferred_free) + synctype[nsynctypes++] = RTWS_DEF_FREE; + else if (gp_normal && !cur_ops->deferred_free) + pr_alert("rcu_torture_writer: gp_normal without primitives.\n"); + if (gp_sync1 && cur_ops->sync) + synctype[nsynctypes++] = RTWS_SYNC; + else if (gp_sync && !cur_ops->sync) + pr_alert("rcu_torture_writer: gp_sync without primitives.\n"); + if (WARN_ONCE(nsynctypes == 0, + "rcu_torture_writer: No update-side primitives.\n")) { + /* + * No updates primitives, so don't try updating. + * The resulting test won't be testing much, hence the + * above WARN_ONCE(). + */ + rcu_torture_writer_state = RTWS_STOPPING; + torture_kthread_stopping("rcu_torture_writer"); + } + + do { + rcu_torture_writer_state = RTWS_FIXED_DELAY; + schedule_timeout_uninterruptible(1); + rp = rcu_torture_alloc(); + if (rp == NULL) + continue; + rp->rtort_pipe_count = 0; + rcu_torture_writer_state = RTWS_DELAY; + udelay(torture_random(&rand) & 0x3ff); + rcu_torture_writer_state = RTWS_REPLACE; + old_rp = rcu_dereference_check(rcu_torture_current, + current == writer_task); + rp->rtort_mbtest = 1; + rcu_assign_pointer(rcu_torture_current, rp); + smp_wmb(); /* Mods to old_rp must follow rcu_assign_pointer() */ + if (old_rp) { + i = old_rp->rtort_pipe_count; + if (i > RCU_TORTURE_PIPE_LEN) + i = RCU_TORTURE_PIPE_LEN; + atomic_inc(&rcu_torture_wcount[i]); + old_rp->rtort_pipe_count++; + switch (synctype[torture_random(&rand) % nsynctypes]) { + case RTWS_DEF_FREE: + rcu_torture_writer_state = RTWS_DEF_FREE; + cur_ops->deferred_free(old_rp); + break; + case RTWS_EXP_SYNC: + rcu_torture_writer_state = RTWS_EXP_SYNC; + cur_ops->exp_sync(); + rcu_torture_pipe_update(old_rp); + break; + case RTWS_COND_GET: + rcu_torture_writer_state = RTWS_COND_GET; + gp_snap = cur_ops->get_state(); + i = torture_random(&rand) % 16; + if (i != 0) + schedule_timeout_interruptible(i); + udelay(torture_random(&rand) % 1000); + rcu_torture_writer_state = RTWS_COND_SYNC; + cur_ops->cond_sync(gp_snap); + rcu_torture_pipe_update(old_rp); + break; + case RTWS_SYNC: + rcu_torture_writer_state = RTWS_SYNC; + cur_ops->sync(); + rcu_torture_pipe_update(old_rp); + break; + default: + WARN_ON_ONCE(1); + break; + } + } + rcutorture_record_progress(++rcu_torture_current_version); + /* Cycle through nesting levels of rcu_expedite_gp() calls. */ + if (can_expedite && + !(torture_random(&rand) & 0xff & (!!expediting - 1))) { + WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited()); + if (expediting >= 0) + rcu_expedite_gp(); + else + rcu_unexpedite_gp(); + if (++expediting > 3) + expediting = -expediting; + } + rcu_torture_writer_state = RTWS_STUTTER; + stutter_wait("rcu_torture_writer"); + } while (!torture_must_stop()); + /* Reset expediting back to unexpedited. */ + if (expediting > 0) + expediting = -expediting; + while (can_expedite && expediting++ < 0) + rcu_unexpedite_gp(); + WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited()); + rcu_torture_writer_state = RTWS_STOPPING; + torture_kthread_stopping("rcu_torture_writer"); + return 0; +} + +/* + * RCU torture fake writer kthread. Repeatedly calls sync, with a random + * delay between calls. + */ +static int +rcu_torture_fakewriter(void *arg) +{ + DEFINE_TORTURE_RANDOM(rand); + + VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started"); + set_user_nice(current, MAX_NICE); + + do { + schedule_timeout_uninterruptible(1 + torture_random(&rand)%10); + udelay(torture_random(&rand) & 0x3ff); + if (cur_ops->cb_barrier != NULL && + torture_random(&rand) % (nfakewriters * 8) == 0) { + cur_ops->cb_barrier(); + } else if (gp_normal == gp_exp) { + if (torture_random(&rand) & 0x80) + cur_ops->sync(); + else + cur_ops->exp_sync(); + } else if (gp_normal) { + cur_ops->sync(); + } else { + cur_ops->exp_sync(); + } + stutter_wait("rcu_torture_fakewriter"); + } while (!torture_must_stop()); + + torture_kthread_stopping("rcu_torture_fakewriter"); + return 0; +} + +static void rcutorture_trace_dump(void) +{ + static atomic_t beenhere = ATOMIC_INIT(0); + + if (atomic_read(&beenhere)) + return; + if (atomic_xchg(&beenhere, 1) != 0) + return; + ftrace_dump(DUMP_ALL); +} + +/* + * RCU torture reader from timer handler. Dereferences rcu_torture_current, + * incrementing the corresponding element of the pipeline array. The + * counter in the element should never be greater than 1, otherwise, the + * RCU implementation is broken. + */ +static void rcu_torture_timer(unsigned long unused) +{ + int idx; + unsigned long started; + unsigned long completed; + static DEFINE_TORTURE_RANDOM(rand); + static DEFINE_SPINLOCK(rand_lock); + struct rcu_torture *p; + int pipe_count; + unsigned long long ts; + + idx = cur_ops->readlock(); + if (cur_ops->started) + started = cur_ops->started(); + else + started = cur_ops->completed(); + ts = rcu_trace_clock_local(); + p = rcu_dereference_check(rcu_torture_current, + rcu_read_lock_bh_held() || + rcu_read_lock_sched_held() || + srcu_read_lock_held(&srcu_ctl)); + if (p == NULL) { + /* Leave because rcu_torture_writer is not yet underway */ + cur_ops->readunlock(idx); + return; + } + if (p->rtort_mbtest == 0) + atomic_inc(&n_rcu_torture_mberror); + spin_lock(&rand_lock); + cur_ops->read_delay(&rand); + n_rcu_torture_timers++; + spin_unlock(&rand_lock); + preempt_disable(); + pipe_count = p->rtort_pipe_count; + if (pipe_count > RCU_TORTURE_PIPE_LEN) { + /* Should not happen, but... */ + pipe_count = RCU_TORTURE_PIPE_LEN; + } + completed = cur_ops->completed(); + if (pipe_count > 1) { + do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts, + started, completed); + rcutorture_trace_dump(); + } + __this_cpu_inc(rcu_torture_count[pipe_count]); + completed = completed - started; + if (cur_ops->started) + completed++; + if (completed > RCU_TORTURE_PIPE_LEN) { + /* Should not happen, but... */ + completed = RCU_TORTURE_PIPE_LEN; + } + __this_cpu_inc(rcu_torture_batch[completed]); + preempt_enable(); + cur_ops->readunlock(idx); +} + +/* + * RCU torture reader kthread. Repeatedly dereferences rcu_torture_current, + * incrementing the corresponding element of the pipeline array. The + * counter in the element should never be greater than 1, otherwise, the + * RCU implementation is broken. + */ +static int +rcu_torture_reader(void *arg) +{ + unsigned long started; + unsigned long completed; + int idx; + DEFINE_TORTURE_RANDOM(rand); + struct rcu_torture *p; + int pipe_count; + struct timer_list t; + unsigned long long ts; + + VERBOSE_TOROUT_STRING("rcu_torture_reader task started"); + set_user_nice(current, MAX_NICE); + if (irqreader && cur_ops->irq_capable) + setup_timer_on_stack(&t, rcu_torture_timer, 0); + + do { + if (irqreader && cur_ops->irq_capable) { + if (!timer_pending(&t)) + mod_timer(&t, jiffies + 1); + } + idx = cur_ops->readlock(); + if (cur_ops->started) + started = cur_ops->started(); + else + started = cur_ops->completed(); + ts = rcu_trace_clock_local(); + p = rcu_dereference_check(rcu_torture_current, + rcu_read_lock_bh_held() || + rcu_read_lock_sched_held() || + srcu_read_lock_held(&srcu_ctl)); + if (p == NULL) { + /* Wait for rcu_torture_writer to get underway */ + cur_ops->readunlock(idx); + schedule_timeout_interruptible(HZ); + continue; + } + if (p->rtort_mbtest == 0) + atomic_inc(&n_rcu_torture_mberror); + cur_ops->read_delay(&rand); + preempt_disable(); + pipe_count = p->rtort_pipe_count; + if (pipe_count > RCU_TORTURE_PIPE_LEN) { + /* Should not happen, but... */ + pipe_count = RCU_TORTURE_PIPE_LEN; + } + completed = cur_ops->completed(); + if (pipe_count > 1) { + do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, + ts, started, completed); + rcutorture_trace_dump(); + } + __this_cpu_inc(rcu_torture_count[pipe_count]); + completed = completed - started; + if (cur_ops->started) + completed++; + if (completed > RCU_TORTURE_PIPE_LEN) { + /* Should not happen, but... */ + completed = RCU_TORTURE_PIPE_LEN; + } + __this_cpu_inc(rcu_torture_batch[completed]); + preempt_enable(); + cur_ops->readunlock(idx); + cond_resched_rcu_qs(); + stutter_wait("rcu_torture_reader"); + } while (!torture_must_stop()); + if (irqreader && cur_ops->irq_capable) { + del_timer_sync(&t); + destroy_timer_on_stack(&t); + } + torture_kthread_stopping("rcu_torture_reader"); + return 0; +} + +/* + * Print torture statistics. Caller must ensure that there is only + * one call to this function at a given time!!! This is normally + * accomplished by relying on the module system to only have one copy + * of the module loaded, and then by giving the rcu_torture_stats + * kthread full control (or the init/cleanup functions when rcu_torture_stats + * thread is not running). + */ +static void +rcu_torture_stats_print(void) +{ + int cpu; + int i; + long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 }; + long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 }; + static unsigned long rtcv_snap = ULONG_MAX; + + for_each_possible_cpu(cpu) { + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { + pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i]; + batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i]; + } + } + for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) { + if (pipesummary[i] != 0) + break; + } + + pr_alert("%s%s ", torture_type, TORTURE_FLAG); + pr_cont("rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ", + rcu_torture_current, + rcu_torture_current_version, + list_empty(&rcu_torture_freelist), + atomic_read(&n_rcu_torture_alloc), + atomic_read(&n_rcu_torture_alloc_fail), + atomic_read(&n_rcu_torture_free)); + pr_cont("rtmbe: %d rtbke: %ld rtbre: %ld ", + atomic_read(&n_rcu_torture_mberror), + n_rcu_torture_boost_ktrerror, + n_rcu_torture_boost_rterror); + pr_cont("rtbf: %ld rtb: %ld nt: %ld ", + n_rcu_torture_boost_failure, + n_rcu_torture_boosts, + n_rcu_torture_timers); + torture_onoff_stats(); + pr_cont("barrier: %ld/%ld:%ld ", + n_barrier_successes, + n_barrier_attempts, + n_rcu_torture_barrier_error); + pr_cont("cbflood: %ld\n", atomic_long_read(&n_cbfloods)); + + pr_alert("%s%s ", torture_type, TORTURE_FLAG); + if (atomic_read(&n_rcu_torture_mberror) != 0 || + n_rcu_torture_barrier_error != 0 || + n_rcu_torture_boost_ktrerror != 0 || + n_rcu_torture_boost_rterror != 0 || + n_rcu_torture_boost_failure != 0 || + i > 1) { + pr_cont("%s", "!!! "); + atomic_inc(&n_rcu_torture_error); + WARN_ON_ONCE(1); + } + pr_cont("Reader Pipe: "); + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) + pr_cont(" %ld", pipesummary[i]); + pr_cont("\n"); + + pr_alert("%s%s ", torture_type, TORTURE_FLAG); + pr_cont("Reader Batch: "); + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) + pr_cont(" %ld", batchsummary[i]); + pr_cont("\n"); + + pr_alert("%s%s ", torture_type, TORTURE_FLAG); + pr_cont("Free-Block Circulation: "); + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { + pr_cont(" %d", atomic_read(&rcu_torture_wcount[i])); + } + pr_cont("\n"); + + if (cur_ops->stats) + cur_ops->stats(); + if (rtcv_snap == rcu_torture_current_version && + rcu_torture_current != NULL) { + int __maybe_unused flags; + unsigned long __maybe_unused gpnum; + unsigned long __maybe_unused completed; + + rcutorture_get_gp_data(cur_ops->ttype, + &flags, &gpnum, &completed); + pr_alert("??? Writer stall state %d g%lu c%lu f%#x\n", + rcu_torture_writer_state, + gpnum, completed, flags); + show_rcu_gp_kthreads(); + rcutorture_trace_dump(); + } + rtcv_snap = rcu_torture_current_version; +} + +/* + * Periodically prints torture statistics, if periodic statistics printing + * was specified via the stat_interval module parameter. + */ +static int +rcu_torture_stats(void *arg) +{ + VERBOSE_TOROUT_STRING("rcu_torture_stats task started"); + do { + schedule_timeout_interruptible(stat_interval * HZ); + rcu_torture_stats_print(); + torture_shutdown_absorb("rcu_torture_stats"); + } while (!torture_must_stop()); + torture_kthread_stopping("rcu_torture_stats"); + return 0; +} + +static inline void +rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag) +{ + pr_alert("%s" TORTURE_FLAG + "--- %s: nreaders=%d nfakewriters=%d " + "stat_interval=%d verbose=%d test_no_idle_hz=%d " + "shuffle_interval=%d stutter=%d irqreader=%d " + "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d " + "test_boost=%d/%d test_boost_interval=%d " + "test_boost_duration=%d shutdown_secs=%d " + "stall_cpu=%d stall_cpu_holdoff=%d " + "n_barrier_cbs=%d " + "onoff_interval=%d onoff_holdoff=%d\n", + torture_type, tag, nrealreaders, nfakewriters, + stat_interval, verbose, test_no_idle_hz, shuffle_interval, + stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter, + test_boost, cur_ops->can_boost, + test_boost_interval, test_boost_duration, shutdown_secs, + stall_cpu, stall_cpu_holdoff, + n_barrier_cbs, + onoff_interval, onoff_holdoff); +} + +static void rcutorture_booster_cleanup(int cpu) +{ + struct task_struct *t; + + if (boost_tasks[cpu] == NULL) + return; + mutex_lock(&boost_mutex); + t = boost_tasks[cpu]; + boost_tasks[cpu] = NULL; + mutex_unlock(&boost_mutex); + + /* This must be outside of the mutex, otherwise deadlock! */ + torture_stop_kthread(rcu_torture_boost, t); +} + +static int rcutorture_booster_init(int cpu) +{ + int retval; + + if (boost_tasks[cpu] != NULL) + return 0; /* Already created, nothing more to do. */ + + /* Don't allow time recalculation while creating a new task. */ + mutex_lock(&boost_mutex); + VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task"); + boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL, + cpu_to_node(cpu), + "rcu_torture_boost"); + if (IS_ERR(boost_tasks[cpu])) { + retval = PTR_ERR(boost_tasks[cpu]); + VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed"); + n_rcu_torture_boost_ktrerror++; + boost_tasks[cpu] = NULL; + mutex_unlock(&boost_mutex); + return retval; + } + kthread_bind(boost_tasks[cpu], cpu); + wake_up_process(boost_tasks[cpu]); + mutex_unlock(&boost_mutex); + return 0; +} + +/* + * CPU-stall kthread. It waits as specified by stall_cpu_holdoff, then + * induces a CPU stall for the time specified by stall_cpu. + */ +static int rcu_torture_stall(void *args) +{ + unsigned long stop_at; + + VERBOSE_TOROUT_STRING("rcu_torture_stall task started"); + if (stall_cpu_holdoff > 0) { + VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff"); + schedule_timeout_interruptible(stall_cpu_holdoff * HZ); + VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff"); + } + if (!kthread_should_stop()) { + stop_at = get_seconds() + stall_cpu; + /* RCU CPU stall is expected behavior in following code. */ + pr_alert("rcu_torture_stall start.\n"); + rcu_read_lock(); + preempt_disable(); + while (ULONG_CMP_LT(get_seconds(), stop_at)) + continue; /* Induce RCU CPU stall warning. */ + preempt_enable(); + rcu_read_unlock(); + pr_alert("rcu_torture_stall end.\n"); + } + torture_shutdown_absorb("rcu_torture_stall"); + while (!kthread_should_stop()) + schedule_timeout_interruptible(10 * HZ); + return 0; +} + +/* Spawn CPU-stall kthread, if stall_cpu specified. */ +static int __init rcu_torture_stall_init(void) +{ + if (stall_cpu <= 0) + return 0; + return torture_create_kthread(rcu_torture_stall, NULL, stall_task); +} + +/* Callback function for RCU barrier testing. */ +static void rcu_torture_barrier_cbf(struct rcu_head *rcu) +{ + atomic_inc(&barrier_cbs_invoked); +} + +/* kthread function to register callbacks used to test RCU barriers. */ +static int rcu_torture_barrier_cbs(void *arg) +{ + long myid = (long)arg; + bool lastphase = 0; + bool newphase; + struct rcu_head rcu; + + init_rcu_head_on_stack(&rcu); + VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task started"); + set_user_nice(current, MAX_NICE); + do { + wait_event(barrier_cbs_wq[myid], + (newphase = + ACCESS_ONCE(barrier_phase)) != lastphase || + torture_must_stop()); + lastphase = newphase; + smp_mb(); /* ensure barrier_phase load before ->call(). */ + if (torture_must_stop()) + break; + cur_ops->call(&rcu, rcu_torture_barrier_cbf); + if (atomic_dec_and_test(&barrier_cbs_count)) + wake_up(&barrier_wq); + } while (!torture_must_stop()); + if (cur_ops->cb_barrier != NULL) + cur_ops->cb_barrier(); + destroy_rcu_head_on_stack(&rcu); + torture_kthread_stopping("rcu_torture_barrier_cbs"); + return 0; +} + +/* kthread function to drive and coordinate RCU barrier testing. */ +static int rcu_torture_barrier(void *arg) +{ + int i; + + VERBOSE_TOROUT_STRING("rcu_torture_barrier task starting"); + do { + atomic_set(&barrier_cbs_invoked, 0); + atomic_set(&barrier_cbs_count, n_barrier_cbs); + smp_mb(); /* Ensure barrier_phase after prior assignments. */ + barrier_phase = !barrier_phase; + for (i = 0; i < n_barrier_cbs; i++) + wake_up(&barrier_cbs_wq[i]); + wait_event(barrier_wq, + atomic_read(&barrier_cbs_count) == 0 || + torture_must_stop()); + if (torture_must_stop()) + break; + n_barrier_attempts++; + cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */ + if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) { + n_rcu_torture_barrier_error++; + pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n", + atomic_read(&barrier_cbs_invoked), + n_barrier_cbs); + WARN_ON_ONCE(1); + } + n_barrier_successes++; + schedule_timeout_interruptible(HZ / 10); + } while (!torture_must_stop()); + torture_kthread_stopping("rcu_torture_barrier"); + return 0; +} + +/* Initialize RCU barrier testing. */ +static int rcu_torture_barrier_init(void) +{ + int i; + int ret; + + if (n_barrier_cbs == 0) + return 0; + if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) { + pr_alert("%s" TORTURE_FLAG + " Call or barrier ops missing for %s,\n", + torture_type, cur_ops->name); + pr_alert("%s" TORTURE_FLAG + " RCU barrier testing omitted from run.\n", + torture_type); + return 0; + } + atomic_set(&barrier_cbs_count, 0); + atomic_set(&barrier_cbs_invoked, 0); + barrier_cbs_tasks = + kzalloc(n_barrier_cbs * sizeof(barrier_cbs_tasks[0]), + GFP_KERNEL); + barrier_cbs_wq = + kzalloc(n_barrier_cbs * sizeof(barrier_cbs_wq[0]), + GFP_KERNEL); + if (barrier_cbs_tasks == NULL || !barrier_cbs_wq) + return -ENOMEM; + for (i = 0; i < n_barrier_cbs; i++) { + init_waitqueue_head(&barrier_cbs_wq[i]); + ret = torture_create_kthread(rcu_torture_barrier_cbs, + (void *)(long)i, + barrier_cbs_tasks[i]); + if (ret) + return ret; + } + return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task); +} + +/* Clean up after RCU barrier testing. */ +static void rcu_torture_barrier_cleanup(void) +{ + int i; + + torture_stop_kthread(rcu_torture_barrier, barrier_task); + if (barrier_cbs_tasks != NULL) { + for (i = 0; i < n_barrier_cbs; i++) + torture_stop_kthread(rcu_torture_barrier_cbs, + barrier_cbs_tasks[i]); + kfree(barrier_cbs_tasks); + barrier_cbs_tasks = NULL; + } + if (barrier_cbs_wq != NULL) { + kfree(barrier_cbs_wq); + barrier_cbs_wq = NULL; + } +} + +static int rcutorture_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + long cpu = (long)hcpu; + + switch (action) { + case CPU_ONLINE: + case CPU_DOWN_FAILED: + (void)rcutorture_booster_init(cpu); + break; + case CPU_DOWN_PREPARE: + rcutorture_booster_cleanup(cpu); + break; + default: + break; + } + return NOTIFY_OK; +} + +static struct notifier_block rcutorture_cpu_nb = { + .notifier_call = rcutorture_cpu_notify, +}; + +static void +rcu_torture_cleanup(void) +{ + int i; + + rcutorture_record_test_transition(); + if (torture_cleanup_begin()) { + if (cur_ops->cb_barrier != NULL) + cur_ops->cb_barrier(); + return; + } + + rcu_torture_barrier_cleanup(); + torture_stop_kthread(rcu_torture_stall, stall_task); + torture_stop_kthread(rcu_torture_writer, writer_task); + + if (reader_tasks) { + for (i = 0; i < nrealreaders; i++) + torture_stop_kthread(rcu_torture_reader, + reader_tasks[i]); + kfree(reader_tasks); + } + rcu_torture_current = NULL; + + if (fakewriter_tasks) { + for (i = 0; i < nfakewriters; i++) { + torture_stop_kthread(rcu_torture_fakewriter, + fakewriter_tasks[i]); + } + kfree(fakewriter_tasks); + fakewriter_tasks = NULL; + } + + torture_stop_kthread(rcu_torture_stats, stats_task); + torture_stop_kthread(rcu_torture_fqs, fqs_task); + for (i = 0; i < ncbflooders; i++) + torture_stop_kthread(rcu_torture_cbflood, cbflood_task[i]); + if ((test_boost == 1 && cur_ops->can_boost) || + test_boost == 2) { + unregister_cpu_notifier(&rcutorture_cpu_nb); + for_each_possible_cpu(i) + rcutorture_booster_cleanup(i); + } + + /* Wait for all RCU callbacks to fire. */ + + if (cur_ops->cb_barrier != NULL) + cur_ops->cb_barrier(); + + rcu_torture_stats_print(); /* -After- the stats thread is stopped! */ + + if (atomic_read(&n_rcu_torture_error) || n_rcu_torture_barrier_error) + rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE"); + else if (torture_onoff_failures()) + rcu_torture_print_module_parms(cur_ops, + "End of test: RCU_HOTPLUG"); + else + rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS"); + torture_cleanup_end(); +} + +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +static void rcu_torture_leak_cb(struct rcu_head *rhp) +{ +} + +static void rcu_torture_err_cb(struct rcu_head *rhp) +{ + /* + * This -might- happen due to race conditions, but is unlikely. + * The scenario that leads to this happening is that the + * first of the pair of duplicate callbacks is queued, + * someone else starts a grace period that includes that + * callback, then the second of the pair must wait for the + * next grace period. Unlikely, but can happen. If it + * does happen, the debug-objects subsystem won't have splatted. + */ + pr_alert("rcutorture: duplicated callback was invoked.\n"); +} +#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + +/* + * Verify that double-free causes debug-objects to complain, but only + * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y. Otherwise, say that the test + * cannot be carried out. + */ +static void rcu_test_debug_objects(void) +{ +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD + struct rcu_head rh1; + struct rcu_head rh2; + + init_rcu_head_on_stack(&rh1); + init_rcu_head_on_stack(&rh2); + pr_alert("rcutorture: WARN: Duplicate call_rcu() test starting.\n"); + + /* Try to queue the rh2 pair of callbacks for the same grace period. */ + preempt_disable(); /* Prevent preemption from interrupting test. */ + rcu_read_lock(); /* Make it impossible to finish a grace period. */ + call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */ + local_irq_disable(); /* Make it harder to start a new grace period. */ + call_rcu(&rh2, rcu_torture_leak_cb); + call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */ + local_irq_enable(); + rcu_read_unlock(); + preempt_enable(); + + /* Wait for them all to get done so we can safely return. */ + rcu_barrier(); + pr_alert("rcutorture: WARN: Duplicate call_rcu() test complete.\n"); + destroy_rcu_head_on_stack(&rh1); + destroy_rcu_head_on_stack(&rh2); +#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + pr_alert("rcutorture: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n"); +#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +} + +static int __init +rcu_torture_init(void) +{ + int i; + int cpu; + int firsterr = 0; + static struct rcu_torture_ops *torture_ops[] = { + &rcu_ops, &rcu_bh_ops, &rcu_busted_ops, &srcu_ops, &sched_ops, + RCUTORTURE_TASKS_OPS + }; + + if (!torture_init_begin(torture_type, verbose, &torture_runnable)) + return -EBUSY; + + /* Process args and tell the world that the torturer is on the job. */ + for (i = 0; i < ARRAY_SIZE(torture_ops); i++) { + cur_ops = torture_ops[i]; + if (strcmp(torture_type, cur_ops->name) == 0) + break; + } + if (i == ARRAY_SIZE(torture_ops)) { + pr_alert("rcu-torture: invalid torture type: \"%s\"\n", + torture_type); + pr_alert("rcu-torture types:"); + for (i = 0; i < ARRAY_SIZE(torture_ops); i++) + pr_alert(" %s", torture_ops[i]->name); + pr_alert("\n"); + torture_init_end(); + return -EINVAL; + } + if (cur_ops->fqs == NULL && fqs_duration != 0) { + pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n"); + fqs_duration = 0; + } + if (cur_ops->init) + cur_ops->init(); /* no "goto unwind" prior to this point!!! */ + + if (nreaders >= 0) { + nrealreaders = nreaders; + } else { + nrealreaders = num_online_cpus() - 1; + if (nrealreaders <= 0) + nrealreaders = 1; + } + rcu_torture_print_module_parms(cur_ops, "Start of test"); + + /* Set up the freelist. */ + + INIT_LIST_HEAD(&rcu_torture_freelist); + for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) { + rcu_tortures[i].rtort_mbtest = 0; + list_add_tail(&rcu_tortures[i].rtort_free, + &rcu_torture_freelist); + } + + /* Initialize the statistics so that each run gets its own numbers. */ + + rcu_torture_current = NULL; + rcu_torture_current_version = 0; + atomic_set(&n_rcu_torture_alloc, 0); + atomic_set(&n_rcu_torture_alloc_fail, 0); + atomic_set(&n_rcu_torture_free, 0); + atomic_set(&n_rcu_torture_mberror, 0); + atomic_set(&n_rcu_torture_error, 0); + n_rcu_torture_barrier_error = 0; + n_rcu_torture_boost_ktrerror = 0; + n_rcu_torture_boost_rterror = 0; + n_rcu_torture_boost_failure = 0; + n_rcu_torture_boosts = 0; + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) + atomic_set(&rcu_torture_wcount[i], 0); + for_each_possible_cpu(cpu) { + for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { + per_cpu(rcu_torture_count, cpu)[i] = 0; + per_cpu(rcu_torture_batch, cpu)[i] = 0; + } + } + + /* Start up the kthreads. */ + + firsterr = torture_create_kthread(rcu_torture_writer, NULL, + writer_task); + if (firsterr) + goto unwind; + fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]), + GFP_KERNEL); + if (fakewriter_tasks == NULL) { + VERBOSE_TOROUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + for (i = 0; i < nfakewriters; i++) { + firsterr = torture_create_kthread(rcu_torture_fakewriter, + NULL, fakewriter_tasks[i]); + if (firsterr) + goto unwind; + } + reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]), + GFP_KERNEL); + if (reader_tasks == NULL) { + VERBOSE_TOROUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + for (i = 0; i < nrealreaders; i++) { + firsterr = torture_create_kthread(rcu_torture_reader, NULL, + reader_tasks[i]); + if (firsterr) + goto unwind; + } + if (stat_interval > 0) { + firsterr = torture_create_kthread(rcu_torture_stats, NULL, + stats_task); + if (firsterr) + goto unwind; + } + if (test_no_idle_hz) { + firsterr = torture_shuffle_init(shuffle_interval * HZ); + if (firsterr) + goto unwind; + } + if (stutter < 0) + stutter = 0; + if (stutter) { + firsterr = torture_stutter_init(stutter * HZ); + if (firsterr) + goto unwind; + } + if (fqs_duration < 0) + fqs_duration = 0; + if (fqs_duration) { + /* Create the fqs thread */ + firsterr = torture_create_kthread(rcu_torture_fqs, NULL, + fqs_task); + if (firsterr) + goto unwind; + } + if (test_boost_interval < 1) + test_boost_interval = 1; + if (test_boost_duration < 2) + test_boost_duration = 2; + if ((test_boost == 1 && cur_ops->can_boost) || + test_boost == 2) { + + boost_starttime = jiffies + test_boost_interval * HZ; + register_cpu_notifier(&rcutorture_cpu_nb); + for_each_possible_cpu(i) { + if (cpu_is_offline(i)) + continue; /* Heuristic: CPU can go offline. */ + firsterr = rcutorture_booster_init(i); + if (firsterr) + goto unwind; + } + } + firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup); + if (firsterr) + goto unwind; + firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval * HZ); + if (firsterr) + goto unwind; + firsterr = rcu_torture_stall_init(); + if (firsterr) + goto unwind; + firsterr = rcu_torture_barrier_init(); + if (firsterr) + goto unwind; + if (object_debug) + rcu_test_debug_objects(); + if (cbflood_n_burst > 0) { + /* Create the cbflood threads */ + ncbflooders = (num_online_cpus() + 3) / 4; + cbflood_task = kcalloc(ncbflooders, sizeof(*cbflood_task), + GFP_KERNEL); + if (!cbflood_task) { + VERBOSE_TOROUT_ERRSTRING("out of memory"); + firsterr = -ENOMEM; + goto unwind; + } + for (i = 0; i < ncbflooders; i++) { + firsterr = torture_create_kthread(rcu_torture_cbflood, + NULL, + cbflood_task[i]); + if (firsterr) + goto unwind; + } + } + rcutorture_record_test_transition(); + torture_init_end(); + return 0; + +unwind: + torture_init_end(); + rcu_torture_cleanup(); + return firsterr; +} + +module_init(rcu_torture_init); +module_exit(rcu_torture_cleanup); diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c new file mode 100644 index 000000000..cad76e76b --- /dev/null +++ b/kernel/rcu/srcu.c @@ -0,0 +1,676 @@ +/* + * Sleepable Read-Copy Update mechanism for mutual exclusion. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright (C) IBM Corporation, 2006 + * Copyright (C) Fujitsu, 2012 + * + * Author: Paul McKenney <paulmck@us.ibm.com> + * Lai Jiangshan <laijs@cn.fujitsu.com> + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU/ *.txt + * + */ + +#include <linux/export.h> +#include <linux/mutex.h> +#include <linux/percpu.h> +#include <linux/preempt.h> +#include <linux/rcupdate.h> +#include <linux/sched.h> +#include <linux/smp.h> +#include <linux/delay.h> +#include <linux/srcu.h> + +#include "rcu.h" + +/* + * Initialize an rcu_batch structure to empty. + */ +static inline void rcu_batch_init(struct rcu_batch *b) +{ + b->head = NULL; + b->tail = &b->head; +} + +/* + * Enqueue a callback onto the tail of the specified rcu_batch structure. + */ +static inline void rcu_batch_queue(struct rcu_batch *b, struct rcu_head *head) +{ + *b->tail = head; + b->tail = &head->next; +} + +/* + * Is the specified rcu_batch structure empty? + */ +static inline bool rcu_batch_empty(struct rcu_batch *b) +{ + return b->tail == &b->head; +} + +/* + * Remove the callback at the head of the specified rcu_batch structure + * and return a pointer to it, or return NULL if the structure is empty. + */ +static inline struct rcu_head *rcu_batch_dequeue(struct rcu_batch *b) +{ + struct rcu_head *head; + + if (rcu_batch_empty(b)) + return NULL; + + head = b->head; + b->head = head->next; + if (b->tail == &head->next) + rcu_batch_init(b); + + return head; +} + +/* + * Move all callbacks from the rcu_batch structure specified by "from" to + * the structure specified by "to". + */ +static inline void rcu_batch_move(struct rcu_batch *to, struct rcu_batch *from) +{ + if (!rcu_batch_empty(from)) { + *to->tail = from->head; + to->tail = from->tail; + rcu_batch_init(from); + } +} + +static int init_srcu_struct_fields(struct srcu_struct *sp) +{ + sp->completed = 0; + spin_lock_init(&sp->queue_lock); + sp->running = false; + rcu_batch_init(&sp->batch_queue); + rcu_batch_init(&sp->batch_check0); + rcu_batch_init(&sp->batch_check1); + rcu_batch_init(&sp->batch_done); + INIT_DELAYED_WORK(&sp->work, process_srcu); + sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array); + return sp->per_cpu_ref ? 0 : -ENOMEM; +} + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +int __init_srcu_struct(struct srcu_struct *sp, const char *name, + struct lock_class_key *key) +{ + /* Don't re-initialize a lock while it is held. */ + debug_check_no_locks_freed((void *)sp, sizeof(*sp)); + lockdep_init_map(&sp->dep_map, name, key, 0); + return init_srcu_struct_fields(sp); +} +EXPORT_SYMBOL_GPL(__init_srcu_struct); + +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/** + * init_srcu_struct - initialize a sleep-RCU structure + * @sp: structure to initialize. + * + * Must invoke this on a given srcu_struct before passing that srcu_struct + * to any other function. Each srcu_struct represents a separate domain + * of SRCU protection. + */ +int init_srcu_struct(struct srcu_struct *sp) +{ + return init_srcu_struct_fields(sp); +} +EXPORT_SYMBOL_GPL(init_srcu_struct); + +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/* + * Returns approximate total of the readers' ->seq[] values for the + * rank of per-CPU counters specified by idx. + */ +static unsigned long srcu_readers_seq_idx(struct srcu_struct *sp, int idx) +{ + int cpu; + unsigned long sum = 0; + unsigned long t; + + for_each_possible_cpu(cpu) { + t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->seq[idx]); + sum += t; + } + return sum; +} + +/* + * Returns approximate number of readers active on the specified rank + * of the per-CPU ->c[] counters. + */ +static unsigned long srcu_readers_active_idx(struct srcu_struct *sp, int idx) +{ + int cpu; + unsigned long sum = 0; + unsigned long t; + + for_each_possible_cpu(cpu) { + t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx]); + sum += t; + } + return sum; +} + +/* + * Return true if the number of pre-existing readers is determined to + * be stably zero. An example unstable zero can occur if the call + * to srcu_readers_active_idx() misses an __srcu_read_lock() increment, + * but due to task migration, sees the corresponding __srcu_read_unlock() + * decrement. This can happen because srcu_readers_active_idx() takes + * time to sum the array, and might in fact be interrupted or preempted + * partway through the summation. + */ +static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) +{ + unsigned long seq; + + seq = srcu_readers_seq_idx(sp, idx); + + /* + * The following smp_mb() A pairs with the smp_mb() B located in + * __srcu_read_lock(). This pairing ensures that if an + * __srcu_read_lock() increments its counter after the summation + * in srcu_readers_active_idx(), then the corresponding SRCU read-side + * critical section will see any changes made prior to the start + * of the current SRCU grace period. + * + * Also, if the above call to srcu_readers_seq_idx() saw the + * increment of ->seq[], then the call to srcu_readers_active_idx() + * must see the increment of ->c[]. + */ + smp_mb(); /* A */ + + /* + * Note that srcu_readers_active_idx() can incorrectly return + * zero even though there is a pre-existing reader throughout. + * To see this, suppose that task A is in a very long SRCU + * read-side critical section that started on CPU 0, and that + * no other reader exists, so that the sum of the counters + * is equal to one. Then suppose that task B starts executing + * srcu_readers_active_idx(), summing up to CPU 1, and then that + * task C starts reading on CPU 0, so that its increment is not + * summed, but finishes reading on CPU 2, so that its decrement + * -is- summed. Then when task B completes its sum, it will + * incorrectly get zero, despite the fact that task A has been + * in its SRCU read-side critical section the whole time. + * + * We therefore do a validation step should srcu_readers_active_idx() + * return zero. + */ + if (srcu_readers_active_idx(sp, idx) != 0) + return false; + + /* + * The remainder of this function is the validation step. + * The following smp_mb() D pairs with the smp_mb() C in + * __srcu_read_unlock(). If the __srcu_read_unlock() was seen + * by srcu_readers_active_idx() above, then any destructive + * operation performed after the grace period will happen after + * the corresponding SRCU read-side critical section. + * + * Note that there can be at most NR_CPUS worth of readers using + * the old index, which is not enough to overflow even a 32-bit + * integer. (Yes, this does mean that systems having more than + * a billion or so CPUs need to be 64-bit systems.) Therefore, + * the sum of the ->seq[] counters cannot possibly overflow. + * Therefore, the only way that the return values of the two + * calls to srcu_readers_seq_idx() can be equal is if there were + * no increments of the corresponding rank of ->seq[] counts + * in the interim. But the missed-increment scenario laid out + * above includes an increment of the ->seq[] counter by + * the corresponding __srcu_read_lock(). Therefore, if this + * scenario occurs, the return values from the two calls to + * srcu_readers_seq_idx() will differ, and thus the validation + * step below suffices. + */ + smp_mb(); /* D */ + + return srcu_readers_seq_idx(sp, idx) == seq; +} + +/** + * srcu_readers_active - returns approximate number of readers. + * @sp: which srcu_struct to count active readers (holding srcu_read_lock). + * + * Note that this is not an atomic primitive, and can therefore suffer + * severe errors when invoked on an active srcu_struct. That said, it + * can be useful as an error check at cleanup time. + */ +static int srcu_readers_active(struct srcu_struct *sp) +{ + int cpu; + unsigned long sum = 0; + + for_each_possible_cpu(cpu) { + sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[0]); + sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[1]); + } + return sum; +} + +/** + * cleanup_srcu_struct - deconstruct a sleep-RCU structure + * @sp: structure to clean up. + * + * Must invoke this after you are finished using a given srcu_struct that + * was initialized via init_srcu_struct(), else you leak memory. + */ +void cleanup_srcu_struct(struct srcu_struct *sp) +{ + if (WARN_ON(srcu_readers_active(sp))) + return; /* Leakage unless caller handles error. */ + free_percpu(sp->per_cpu_ref); + sp->per_cpu_ref = NULL; +} +EXPORT_SYMBOL_GPL(cleanup_srcu_struct); + +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct. Must be called from process context. + * Returns an index that must be passed to the matching srcu_read_unlock(). + */ +int __srcu_read_lock(struct srcu_struct *sp) +{ + int idx; + + idx = ACCESS_ONCE(sp->completed) & 0x1; + preempt_disable(); + __this_cpu_inc(sp->per_cpu_ref->c[idx]); + smp_mb(); /* B */ /* Avoid leaking the critical section. */ + __this_cpu_inc(sp->per_cpu_ref->seq[idx]); + preempt_enable(); + return idx; +} +EXPORT_SYMBOL_GPL(__srcu_read_lock); + +/* + * Removes the count for the old reader from the appropriate per-CPU + * element of the srcu_struct. Note that this may well be a different + * CPU than that which was incremented by the corresponding srcu_read_lock(). + * Must be called from process context. + */ +void __srcu_read_unlock(struct srcu_struct *sp, int idx) +{ + smp_mb(); /* C */ /* Avoid leaking the critical section. */ + this_cpu_dec(sp->per_cpu_ref->c[idx]); +} +EXPORT_SYMBOL_GPL(__srcu_read_unlock); + +/* + * We use an adaptive strategy for synchronize_srcu() and especially for + * synchronize_srcu_expedited(). We spin for a fixed time period + * (defined below) to allow SRCU readers to exit their read-side critical + * sections. If there are still some readers after 10 microseconds, + * we repeatedly block for 1-millisecond time periods. This approach + * has done well in testing, so there is no need for a config parameter. + */ +#define SRCU_RETRY_CHECK_DELAY 5 +#define SYNCHRONIZE_SRCU_TRYCOUNT 2 +#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT 12 + +/* + * @@@ Wait until all pre-existing readers complete. Such readers + * will have used the index specified by "idx". + * the caller should ensures the ->completed is not changed while checking + * and idx = (->completed & 1) ^ 1 + */ +static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount) +{ + for (;;) { + if (srcu_readers_active_idx_check(sp, idx)) + return true; + if (--trycount <= 0) + return false; + udelay(SRCU_RETRY_CHECK_DELAY); + } +} + +/* + * Increment the ->completed counter so that future SRCU readers will + * use the other rank of the ->c[] and ->seq[] arrays. This allows + * us to wait for pre-existing readers in a starvation-free manner. + */ +static void srcu_flip(struct srcu_struct *sp) +{ + sp->completed++; +} + +/* + * Enqueue an SRCU callback on the specified srcu_struct structure, + * initiating grace-period processing if it is not already running. + * + * Note that all CPUs must agree that the grace period extended beyond + * all pre-existing SRCU read-side critical section. On systems with + * more than one CPU, this means that when "func()" is invoked, each CPU + * is guaranteed to have executed a full memory barrier since the end of + * its last corresponding SRCU read-side critical section whose beginning + * preceded the call to call_rcu(). It also means that each CPU executing + * an SRCU read-side critical section that continues beyond the start of + * "func()" must have executed a memory barrier after the call_rcu() + * but before the beginning of that SRCU read-side critical section. + * Note that these guarantees include CPUs that are offline, idle, or + * executing in user mode, as well as CPUs that are executing in the kernel. + * + * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the + * resulting SRCU callback function "func()", then both CPU A and CPU + * B are guaranteed to execute a full memory barrier during the time + * interval between the call to call_rcu() and the invocation of "func()". + * This guarantee applies even if CPU A and CPU B are the same CPU (but + * again only if the system has more than one CPU). + * + * Of course, these guarantees apply only for invocations of call_srcu(), + * srcu_read_lock(), and srcu_read_unlock() that are all passed the same + * srcu_struct structure. + */ +void call_srcu(struct srcu_struct *sp, struct rcu_head *head, + void (*func)(struct rcu_head *head)) +{ + unsigned long flags; + + head->next = NULL; + head->func = func; + spin_lock_irqsave(&sp->queue_lock, flags); + rcu_batch_queue(&sp->batch_queue, head); + if (!sp->running) { + sp->running = true; + queue_delayed_work(system_power_efficient_wq, &sp->work, 0); + } + spin_unlock_irqrestore(&sp->queue_lock, flags); +} +EXPORT_SYMBOL_GPL(call_srcu); + +static void srcu_advance_batches(struct srcu_struct *sp, int trycount); +static void srcu_reschedule(struct srcu_struct *sp); + +/* + * Helper function for synchronize_srcu() and synchronize_srcu_expedited(). + */ +static void __synchronize_srcu(struct srcu_struct *sp, int trycount) +{ + struct rcu_synchronize rcu; + struct rcu_head *head = &rcu.head; + bool done = false; + + rcu_lockdep_assert(!lock_is_held(&sp->dep_map) && + !lock_is_held(&rcu_bh_lock_map) && + !lock_is_held(&rcu_lock_map) && + !lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section"); + + might_sleep(); + init_completion(&rcu.completion); + + head->next = NULL; + head->func = wakeme_after_rcu; + spin_lock_irq(&sp->queue_lock); + if (!sp->running) { + /* steal the processing owner */ + sp->running = true; + rcu_batch_queue(&sp->batch_check0, head); + spin_unlock_irq(&sp->queue_lock); + + srcu_advance_batches(sp, trycount); + if (!rcu_batch_empty(&sp->batch_done)) { + BUG_ON(sp->batch_done.head != head); + rcu_batch_dequeue(&sp->batch_done); + done = true; + } + /* give the processing owner to work_struct */ + srcu_reschedule(sp); + } else { + rcu_batch_queue(&sp->batch_queue, head); + spin_unlock_irq(&sp->queue_lock); + } + + if (!done) + wait_for_completion(&rcu.completion); +} + +/** + * synchronize_srcu - wait for prior SRCU read-side critical-section completion + * @sp: srcu_struct with which to synchronize. + * + * Wait for the count to drain to zero of both indexes. To avoid the + * possible starvation of synchronize_srcu(), it waits for the count of + * the index=((->completed & 1) ^ 1) to drain to zero at first, + * and then flip the completed and wait for the count of the other index. + * + * Can block; must be called from process context. + * + * Note that it is illegal to call synchronize_srcu() from the corresponding + * SRCU read-side critical section; doing so will result in deadlock. + * However, it is perfectly legal to call synchronize_srcu() on one + * srcu_struct from some other srcu_struct's read-side critical section, + * as long as the resulting graph of srcu_structs is acyclic. + * + * There are memory-ordering constraints implied by synchronize_srcu(). + * On systems with more than one CPU, when synchronize_srcu() returns, + * each CPU is guaranteed to have executed a full memory barrier since + * the end of its last corresponding SRCU-sched read-side critical section + * whose beginning preceded the call to synchronize_srcu(). In addition, + * each CPU having an SRCU read-side critical section that extends beyond + * the return from synchronize_srcu() is guaranteed to have executed a + * full memory barrier after the beginning of synchronize_srcu() and before + * the beginning of that SRCU read-side critical section. Note that these + * guarantees include CPUs that are offline, idle, or executing in user mode, + * as well as CPUs that are executing in the kernel. + * + * Furthermore, if CPU A invoked synchronize_srcu(), which returned + * to its caller on CPU B, then both CPU A and CPU B are guaranteed + * to have executed a full memory barrier during the execution of + * synchronize_srcu(). This guarantee applies even if CPU A and CPU B + * are the same CPU, but again only if the system has more than one CPU. + * + * Of course, these memory-ordering guarantees apply only when + * synchronize_srcu(), srcu_read_lock(), and srcu_read_unlock() are + * passed the same srcu_struct structure. + */ +void synchronize_srcu(struct srcu_struct *sp) +{ + __synchronize_srcu(sp, rcu_gp_is_expedited() + ? SYNCHRONIZE_SRCU_EXP_TRYCOUNT + : SYNCHRONIZE_SRCU_TRYCOUNT); +} +EXPORT_SYMBOL_GPL(synchronize_srcu); + +/** + * synchronize_srcu_expedited - Brute-force SRCU grace period + * @sp: srcu_struct with which to synchronize. + * + * Wait for an SRCU grace period to elapse, but be more aggressive about + * spinning rather than blocking when waiting. + * + * Note that synchronize_srcu_expedited() has the same deadlock and + * memory-ordering properties as does synchronize_srcu(). + */ +void synchronize_srcu_expedited(struct srcu_struct *sp) +{ + __synchronize_srcu(sp, SYNCHRONIZE_SRCU_EXP_TRYCOUNT); +} +EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); + +/** + * srcu_barrier - Wait until all in-flight call_srcu() callbacks complete. + * @sp: srcu_struct on which to wait for in-flight callbacks. + */ +void srcu_barrier(struct srcu_struct *sp) +{ + synchronize_srcu(sp); +} +EXPORT_SYMBOL_GPL(srcu_barrier); + +/** + * srcu_batches_completed - return batches completed. + * @sp: srcu_struct on which to report batch completion. + * + * Report the number of batches, correlated with, but not necessarily + * precisely the same as, the number of grace periods that have elapsed. + */ +unsigned long srcu_batches_completed(struct srcu_struct *sp) +{ + return sp->completed; +} +EXPORT_SYMBOL_GPL(srcu_batches_completed); + +#define SRCU_CALLBACK_BATCH 10 +#define SRCU_INTERVAL 1 + +/* + * Move any new SRCU callbacks to the first stage of the SRCU grace + * period pipeline. + */ +static void srcu_collect_new(struct srcu_struct *sp) +{ + if (!rcu_batch_empty(&sp->batch_queue)) { + spin_lock_irq(&sp->queue_lock); + rcu_batch_move(&sp->batch_check0, &sp->batch_queue); + spin_unlock_irq(&sp->queue_lock); + } +} + +/* + * Core SRCU state machine. Advance callbacks from ->batch_check0 to + * ->batch_check1 and then to ->batch_done as readers drain. + */ +static void srcu_advance_batches(struct srcu_struct *sp, int trycount) +{ + int idx = 1 ^ (sp->completed & 1); + + /* + * Because readers might be delayed for an extended period after + * fetching ->completed for their index, at any point in time there + * might well be readers using both idx=0 and idx=1. We therefore + * need to wait for readers to clear from both index values before + * invoking a callback. + */ + + if (rcu_batch_empty(&sp->batch_check0) && + rcu_batch_empty(&sp->batch_check1)) + return; /* no callbacks need to be advanced */ + + if (!try_check_zero(sp, idx, trycount)) + return; /* failed to advance, will try after SRCU_INTERVAL */ + + /* + * The callbacks in ->batch_check1 have already done with their + * first zero check and flip back when they were enqueued on + * ->batch_check0 in a previous invocation of srcu_advance_batches(). + * (Presumably try_check_zero() returned false during that + * invocation, leaving the callbacks stranded on ->batch_check1.) + * They are therefore ready to invoke, so move them to ->batch_done. + */ + rcu_batch_move(&sp->batch_done, &sp->batch_check1); + + if (rcu_batch_empty(&sp->batch_check0)) + return; /* no callbacks need to be advanced */ + srcu_flip(sp); + + /* + * The callbacks in ->batch_check0 just finished their + * first check zero and flip, so move them to ->batch_check1 + * for future checking on the other idx. + */ + rcu_batch_move(&sp->batch_check1, &sp->batch_check0); + + /* + * SRCU read-side critical sections are normally short, so check + * at least twice in quick succession after a flip. + */ + trycount = trycount < 2 ? 2 : trycount; + if (!try_check_zero(sp, idx^1, trycount)) + return; /* failed to advance, will try after SRCU_INTERVAL */ + + /* + * The callbacks in ->batch_check1 have now waited for all + * pre-existing readers using both idx values. They are therefore + * ready to invoke, so move them to ->batch_done. + */ + rcu_batch_move(&sp->batch_done, &sp->batch_check1); +} + +/* + * Invoke a limited number of SRCU callbacks that have passed through + * their grace period. If there are more to do, SRCU will reschedule + * the workqueue. + */ +static void srcu_invoke_callbacks(struct srcu_struct *sp) +{ + int i; + struct rcu_head *head; + + for (i = 0; i < SRCU_CALLBACK_BATCH; i++) { + head = rcu_batch_dequeue(&sp->batch_done); + if (!head) + break; + local_bh_disable(); + head->func(head); + local_bh_enable(); + } +} + +/* + * Finished one round of SRCU grace period. Start another if there are + * more SRCU callbacks queued, otherwise put SRCU into not-running state. + */ +static void srcu_reschedule(struct srcu_struct *sp) +{ + bool pending = true; + + if (rcu_batch_empty(&sp->batch_done) && + rcu_batch_empty(&sp->batch_check1) && + rcu_batch_empty(&sp->batch_check0) && + rcu_batch_empty(&sp->batch_queue)) { + spin_lock_irq(&sp->queue_lock); + if (rcu_batch_empty(&sp->batch_done) && + rcu_batch_empty(&sp->batch_check1) && + rcu_batch_empty(&sp->batch_check0) && + rcu_batch_empty(&sp->batch_queue)) { + sp->running = false; + pending = false; + } + spin_unlock_irq(&sp->queue_lock); + } + + if (pending) + queue_delayed_work(system_power_efficient_wq, + &sp->work, SRCU_INTERVAL); +} + +/* + * This is the work-queue function that handles SRCU grace periods. + */ +void process_srcu(struct work_struct *work) +{ + struct srcu_struct *sp; + + sp = container_of(work, struct srcu_struct, work.work); + + srcu_collect_new(sp); + srcu_advance_batches(sp, 1); + srcu_invoke_callbacks(sp); + srcu_reschedule(sp); +} +EXPORT_SYMBOL_GPL(process_srcu); diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c new file mode 100644 index 000000000..ec3086879 --- /dev/null +++ b/kernel/rcu/tiny.c @@ -0,0 +1,288 @@ +/* + * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2008 + * + * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU + */ +#include <linux/completion.h> +#include <linux/interrupt.h> +#include <linux/notifier.h> +#include <linux/rcupdate.h> +#include <linux/kernel.h> +#include <linux/export.h> +#include <linux/mutex.h> +#include <linux/sched.h> +#include <linux/types.h> +#include <linux/init.h> +#include <linux/time.h> +#include <linux/cpu.h> +#include <linux/prefetch.h> +#include <linux/ftrace_event.h> + +#include "rcu.h" + +/* Forward declarations for tiny_plugin.h. */ +struct rcu_ctrlblk; +static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp); +static void rcu_process_callbacks(struct softirq_action *unused); +static void __call_rcu(struct rcu_head *head, + void (*func)(struct rcu_head *rcu), + struct rcu_ctrlblk *rcp); + +#include "tiny_plugin.h" + +/* + * Enter idle, which is an extended quiescent state if we have fully + * entered that mode. + */ +void rcu_idle_enter(void) +{ +} +EXPORT_SYMBOL_GPL(rcu_idle_enter); + +/* + * Exit an interrupt handler towards idle. + */ +void rcu_irq_exit(void) +{ +} +EXPORT_SYMBOL_GPL(rcu_irq_exit); + +/* + * Exit idle, so that we are no longer in an extended quiescent state. + */ +void rcu_idle_exit(void) +{ +} +EXPORT_SYMBOL_GPL(rcu_idle_exit); + +/* + * Enter an interrupt handler, moving away from idle. + */ +void rcu_irq_enter(void) +{ +} +EXPORT_SYMBOL_GPL(rcu_irq_enter); + +#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) + +/* + * Test whether RCU thinks that the current CPU is idle. + */ +bool notrace __rcu_is_watching(void) +{ + return true; +} +EXPORT_SYMBOL(__rcu_is_watching); + +#endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */ + +/* + * Helper function for rcu_sched_qs() and rcu_bh_qs(). + * Also irqs are disabled to avoid confusion due to interrupt handlers + * invoking call_rcu(). + */ +static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) +{ + RCU_TRACE(reset_cpu_stall_ticks(rcp)); + if (rcp->donetail != rcp->curtail) { + rcp->donetail = rcp->curtail; + return 1; + } + + return 0; +} + +/* + * Record an rcu quiescent state. And an rcu_bh quiescent state while we + * are at it, given that any rcu quiescent state is also an rcu_bh + * quiescent state. Use "+" instead of "||" to defeat short circuiting. + */ +void rcu_sched_qs(void) +{ + unsigned long flags; + + local_irq_save(flags); + if (rcu_qsctr_help(&rcu_sched_ctrlblk) + + rcu_qsctr_help(&rcu_bh_ctrlblk)) + raise_softirq(RCU_SOFTIRQ); + local_irq_restore(flags); +} + +/* + * Record an rcu_bh quiescent state. + */ +void rcu_bh_qs(void) +{ + unsigned long flags; + + local_irq_save(flags); + if (rcu_qsctr_help(&rcu_bh_ctrlblk)) + raise_softirq(RCU_SOFTIRQ); + local_irq_restore(flags); +} + +/* + * Check to see if the scheduling-clock interrupt came from an extended + * quiescent state, and, if so, tell RCU about it. This function must + * be called from hardirq context. It is normally called from the + * scheduling-clock interrupt. + */ +void rcu_check_callbacks(int user) +{ + RCU_TRACE(check_cpu_stalls()); + if (user) + rcu_sched_qs(); + else if (!in_softirq()) + rcu_bh_qs(); + if (user) + rcu_note_voluntary_context_switch(current); +} + +/* + * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure + * whose grace period has elapsed. + */ +static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) +{ + const char *rn = NULL; + struct rcu_head *next, *list; + unsigned long flags; + RCU_TRACE(int cb_count = 0); + + /* Move the ready-to-invoke callbacks to a local list. */ + local_irq_save(flags); + if (rcp->donetail == &rcp->rcucblist) { + /* No callbacks ready, so just leave. */ + local_irq_restore(flags); + return; + } + RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1)); + list = rcp->rcucblist; + rcp->rcucblist = *rcp->donetail; + *rcp->donetail = NULL; + if (rcp->curtail == rcp->donetail) + rcp->curtail = &rcp->rcucblist; + rcp->donetail = &rcp->rcucblist; + local_irq_restore(flags); + + /* Invoke the callbacks on the local list. */ + RCU_TRACE(rn = rcp->name); + while (list) { + next = list->next; + prefetch(next); + debug_rcu_head_unqueue(list); + local_bh_disable(); + __rcu_reclaim(rn, list); + local_bh_enable(); + list = next; + RCU_TRACE(cb_count++); + } + RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); + RCU_TRACE(trace_rcu_batch_end(rcp->name, + cb_count, 0, need_resched(), + is_idle_task(current), + false)); +} + +static void rcu_process_callbacks(struct softirq_action *unused) +{ + __rcu_process_callbacks(&rcu_sched_ctrlblk); + __rcu_process_callbacks(&rcu_bh_ctrlblk); +} + +/* + * Wait for a grace period to elapse. But it is illegal to invoke + * synchronize_sched() from within an RCU read-side critical section. + * Therefore, any legal call to synchronize_sched() is a quiescent + * state, and so on a UP system, synchronize_sched() need do nothing. + * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the + * benefits of doing might_sleep() to reduce latency.) + * + * Cool, huh? (Due to Josh Triplett.) + * + * But we want to make this a static inline later. The cond_resched() + * currently makes this problematic. + */ +void synchronize_sched(void) +{ + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && + !lock_is_held(&rcu_lock_map) && + !lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_sched() in RCU read-side critical section"); + cond_resched(); +} +EXPORT_SYMBOL_GPL(synchronize_sched); + +/* + * Helper function for call_rcu() and call_rcu_bh(). + */ +static void __call_rcu(struct rcu_head *head, + void (*func)(struct rcu_head *rcu), + struct rcu_ctrlblk *rcp) +{ + unsigned long flags; + + debug_rcu_head_queue(head); + head->func = func; + head->next = NULL; + + local_irq_save(flags); + *rcp->curtail = head; + rcp->curtail = &head->next; + RCU_TRACE(rcp->qlen++); + local_irq_restore(flags); + + if (unlikely(is_idle_task(current))) { + /* force scheduling for rcu_sched_qs() */ + resched_cpu(0); + } +} + +/* + * Post an RCU callback to be invoked after the end of an RCU-sched grace + * period. But since we have but one CPU, that would be after any + * quiescent state. + */ +void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_sched_ctrlblk); +} +EXPORT_SYMBOL_GPL(call_rcu_sched); + +/* + * Post an RCU bottom-half callback to be invoked after any subsequent + * quiescent state. + */ +void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_bh_ctrlblk); +} +EXPORT_SYMBOL_GPL(call_rcu_bh); + +void __init rcu_init(void) +{ + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); + RCU_TRACE(reset_cpu_stall_ticks(&rcu_sched_ctrlblk)); + RCU_TRACE(reset_cpu_stall_ticks(&rcu_bh_ctrlblk)); + + rcu_early_boot_tests(); +} diff --git a/kernel/rcu/tiny_plugin.h b/kernel/rcu/tiny_plugin.h new file mode 100644 index 000000000..f94e209a1 --- /dev/null +++ b/kernel/rcu/tiny_plugin.h @@ -0,0 +1,173 @@ +/* + * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition + * Internal non-public definitions that provide either classic + * or preemptible semantics. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright (c) 2010 Linaro + * + * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#include <linux/kthread.h> +#include <linux/module.h> +#include <linux/debugfs.h> +#include <linux/seq_file.h> + +/* Global control variables for rcupdate callback mechanism. */ +struct rcu_ctrlblk { + struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */ + struct rcu_head **donetail; /* ->next pointer of last "done" CB. */ + struct rcu_head **curtail; /* ->next pointer of last CB. */ + RCU_TRACE(long qlen); /* Number of pending CBs. */ + RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */ + RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */ + RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */ + RCU_TRACE(const char *name); /* Name of RCU type. */ +}; + +/* Definition for rcupdate control block. */ +static struct rcu_ctrlblk rcu_sched_ctrlblk = { + .donetail = &rcu_sched_ctrlblk.rcucblist, + .curtail = &rcu_sched_ctrlblk.rcucblist, + RCU_TRACE(.name = "rcu_sched") +}; + +static struct rcu_ctrlblk rcu_bh_ctrlblk = { + .donetail = &rcu_bh_ctrlblk.rcucblist, + .curtail = &rcu_bh_ctrlblk.rcucblist, + RCU_TRACE(.name = "rcu_bh") +}; + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +#include <linux/kernel_stat.h> + +int rcu_scheduler_active __read_mostly; +EXPORT_SYMBOL_GPL(rcu_scheduler_active); + +/* + * During boot, we forgive RCU lockdep issues. After this function is + * invoked, we start taking RCU lockdep issues seriously. + */ +void __init rcu_scheduler_starting(void) +{ + WARN_ON(nr_context_switches() > 0); + rcu_scheduler_active = 1; +} + +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +#ifdef CONFIG_RCU_TRACE + +static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) +{ + unsigned long flags; + + local_irq_save(flags); + rcp->qlen -= n; + local_irq_restore(flags); +} + +/* + * Dump statistics for TINY_RCU, such as they are. + */ +static int show_tiny_stats(struct seq_file *m, void *unused) +{ + seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); + seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); + return 0; +} + +static int show_tiny_stats_open(struct inode *inode, struct file *file) +{ + return single_open(file, show_tiny_stats, NULL); +} + +static const struct file_operations show_tiny_stats_fops = { + .owner = THIS_MODULE, + .open = show_tiny_stats_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +static struct dentry *rcudir; + +static int __init rcutiny_trace_init(void) +{ + struct dentry *retval; + + rcudir = debugfs_create_dir("rcu", NULL); + if (!rcudir) + goto free_out; + retval = debugfs_create_file("rcudata", 0444, rcudir, + NULL, &show_tiny_stats_fops); + if (!retval) + goto free_out; + return 0; +free_out: + debugfs_remove_recursive(rcudir); + return 1; +} + +static void __exit rcutiny_trace_cleanup(void) +{ + debugfs_remove_recursive(rcudir); +} + +module_init(rcutiny_trace_init); +module_exit(rcutiny_trace_cleanup); + +MODULE_AUTHOR("Paul E. McKenney"); +MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); +MODULE_LICENSE("GPL"); + +static void check_cpu_stall(struct rcu_ctrlblk *rcp) +{ + unsigned long j; + unsigned long js; + + if (rcu_cpu_stall_suppress) + return; + rcp->ticks_this_gp++; + j = jiffies; + js = ACCESS_ONCE(rcp->jiffies_stall); + if (rcp->rcucblist && ULONG_CMP_GE(j, js)) { + pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n", + rcp->name, rcp->ticks_this_gp, DYNTICK_TASK_EXIT_IDLE, + jiffies - rcp->gp_start, rcp->qlen); + dump_stack(); + ACCESS_ONCE(rcp->jiffies_stall) = jiffies + + 3 * rcu_jiffies_till_stall_check() + 3; + } else if (ULONG_CMP_GE(j, js)) { + ACCESS_ONCE(rcp->jiffies_stall) = jiffies + rcu_jiffies_till_stall_check(); + } +} + +static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp) +{ + rcp->ticks_this_gp = 0; + rcp->gp_start = jiffies; + ACCESS_ONCE(rcp->jiffies_stall) = jiffies + rcu_jiffies_till_stall_check(); +} + +static void check_cpu_stalls(void) +{ + RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk)); + RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk)); +} + +#endif /* #ifdef CONFIG_RCU_TRACE */ diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c new file mode 100644 index 000000000..8cf7304b2 --- /dev/null +++ b/kernel/rcu/tree.c @@ -0,0 +1,4136 @@ +/* + * Read-Copy Update mechanism for mutual exclusion + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2008 + * + * Authors: Dipankar Sarma <dipankar@in.ibm.com> + * Manfred Spraul <manfred@colorfullife.com> + * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version + * + * Based on the original work by Paul McKenney <paulmck@us.ibm.com> + * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU + */ +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/rcupdate.h> +#include <linux/interrupt.h> +#include <linux/sched.h> +#include <linux/nmi.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/export.h> +#include <linux/completion.h> +#include <linux/moduleparam.h> +#include <linux/module.h> +#include <linux/percpu.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/mutex.h> +#include <linux/time.h> +#include <linux/kernel_stat.h> +#include <linux/wait.h> +#include <linux/kthread.h> +#include <linux/prefetch.h> +#include <linux/delay.h> +#include <linux/stop_machine.h> +#include <linux/random.h> +#include <linux/ftrace_event.h> +#include <linux/suspend.h> + +#include "tree.h" +#include "rcu.h" + +MODULE_ALIAS("rcutree"); +#ifdef MODULE_PARAM_PREFIX +#undef MODULE_PARAM_PREFIX +#endif +#define MODULE_PARAM_PREFIX "rcutree." + +/* Data structures. */ + +static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; +static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; + +/* + * In order to export the rcu_state name to the tracing tools, it + * needs to be added in the __tracepoint_string section. + * This requires defining a separate variable tp_<sname>_varname + * that points to the string being used, and this will allow + * the tracing userspace tools to be able to decipher the string + * address to the matching string. + */ +#ifdef CONFIG_TRACING +# define DEFINE_RCU_TPS(sname) \ +static char sname##_varname[] = #sname; \ +static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; +# define RCU_STATE_NAME(sname) sname##_varname +#else +# define DEFINE_RCU_TPS(sname) +# define RCU_STATE_NAME(sname) __stringify(sname) +#endif + +#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \ +DEFINE_RCU_TPS(sname) \ +DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data); \ +struct rcu_state sname##_state = { \ + .level = { &sname##_state.node[0] }, \ + .rda = &sname##_data, \ + .call = cr, \ + .fqs_state = RCU_GP_IDLE, \ + .gpnum = 0UL - 300UL, \ + .completed = 0UL - 300UL, \ + .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \ + .orphan_nxttail = &sname##_state.orphan_nxtlist, \ + .orphan_donetail = &sname##_state.orphan_donelist, \ + .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \ + .name = RCU_STATE_NAME(sname), \ + .abbr = sabbr, \ +} + +RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched); +RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); + +static struct rcu_state *rcu_state_p; +LIST_HEAD(rcu_struct_flavors); + +/* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */ +static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF; +module_param(rcu_fanout_leaf, int, 0444); +int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; +static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */ + NUM_RCU_LVL_0, + NUM_RCU_LVL_1, + NUM_RCU_LVL_2, + NUM_RCU_LVL_3, + NUM_RCU_LVL_4, +}; +int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ + +/* + * The rcu_scheduler_active variable transitions from zero to one just + * before the first task is spawned. So when this variable is zero, RCU + * can assume that there is but one task, allowing RCU to (for example) + * optimize synchronize_sched() to a simple barrier(). When this variable + * is one, RCU must actually do all the hard work required to detect real + * grace periods. This variable is also used to suppress boot-time false + * positives from lockdep-RCU error checking. + */ +int rcu_scheduler_active __read_mostly; +EXPORT_SYMBOL_GPL(rcu_scheduler_active); + +/* + * The rcu_scheduler_fully_active variable transitions from zero to one + * during the early_initcall() processing, which is after the scheduler + * is capable of creating new tasks. So RCU processing (for example, + * creating tasks for RCU priority boosting) must be delayed until after + * rcu_scheduler_fully_active transitions from zero to one. We also + * currently delay invocation of any RCU callbacks until after this point. + * + * It might later prove better for people registering RCU callbacks during + * early boot to take responsibility for these callbacks, but one step at + * a time. + */ +static int rcu_scheduler_fully_active __read_mostly; + +static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); +static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); +static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); +static void invoke_rcu_core(void); +static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp); + +/* rcuc/rcub kthread realtime priority */ +static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO; +module_param(kthread_prio, int, 0644); + +/* Delay in jiffies for grace-period initialization delays, debug only. */ +#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT +static int gp_init_delay = CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY; +module_param(gp_init_delay, int, 0644); +#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */ +static const int gp_init_delay; +#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */ +#define PER_RCU_NODE_PERIOD 10 /* Number of grace periods between delays. */ + +/* + * Track the rcutorture test sequence number and the update version + * number within a given test. The rcutorture_testseq is incremented + * on every rcutorture module load and unload, so has an odd value + * when a test is running. The rcutorture_vernum is set to zero + * when rcutorture starts and is incremented on each rcutorture update. + * These variables enable correlating rcutorture output with the + * RCU tracing information. + */ +unsigned long rcutorture_testseq; +unsigned long rcutorture_vernum; + +/* + * Compute the mask of online CPUs for the specified rcu_node structure. + * This will not be stable unless the rcu_node structure's ->lock is + * held, but the bit corresponding to the current CPU will be stable + * in most contexts. + */ +unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp) +{ + return ACCESS_ONCE(rnp->qsmaskinitnext); +} + +/* + * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s + * permit this function to be invoked without holding the root rcu_node + * structure's ->lock, but of course results can be subject to change. + */ +static int rcu_gp_in_progress(struct rcu_state *rsp) +{ + return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); +} + +/* + * Note a quiescent state. Because we do not need to know + * how many quiescent states passed, just if there was at least + * one since the start of the grace period, this just sets a flag. + * The caller must have disabled preemption. + */ +void rcu_sched_qs(void) +{ + if (!__this_cpu_read(rcu_sched_data.passed_quiesce)) { + trace_rcu_grace_period(TPS("rcu_sched"), + __this_cpu_read(rcu_sched_data.gpnum), + TPS("cpuqs")); + __this_cpu_write(rcu_sched_data.passed_quiesce, 1); + } +} + +void rcu_bh_qs(void) +{ + if (!__this_cpu_read(rcu_bh_data.passed_quiesce)) { + trace_rcu_grace_period(TPS("rcu_bh"), + __this_cpu_read(rcu_bh_data.gpnum), + TPS("cpuqs")); + __this_cpu_write(rcu_bh_data.passed_quiesce, 1); + } +} + +static DEFINE_PER_CPU(int, rcu_sched_qs_mask); + +static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { + .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, + .dynticks = ATOMIC_INIT(1), +#ifdef CONFIG_NO_HZ_FULL_SYSIDLE + .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE, + .dynticks_idle = ATOMIC_INIT(1), +#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ +}; + +DEFINE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr); +EXPORT_PER_CPU_SYMBOL_GPL(rcu_qs_ctr); + +/* + * Let the RCU core know that this CPU has gone through the scheduler, + * which is a quiescent state. This is called when the need for a + * quiescent state is urgent, so we burn an atomic operation and full + * memory barriers to let the RCU core know about it, regardless of what + * this CPU might (or might not) do in the near future. + * + * We inform the RCU core by emulating a zero-duration dyntick-idle + * period, which we in turn do by incrementing the ->dynticks counter + * by two. + */ +static void rcu_momentary_dyntick_idle(void) +{ + unsigned long flags; + struct rcu_data *rdp; + struct rcu_dynticks *rdtp; + int resched_mask; + struct rcu_state *rsp; + + local_irq_save(flags); + + /* + * Yes, we can lose flag-setting operations. This is OK, because + * the flag will be set again after some delay. + */ + resched_mask = raw_cpu_read(rcu_sched_qs_mask); + raw_cpu_write(rcu_sched_qs_mask, 0); + + /* Find the flavor that needs a quiescent state. */ + for_each_rcu_flavor(rsp) { + rdp = raw_cpu_ptr(rsp->rda); + if (!(resched_mask & rsp->flavor_mask)) + continue; + smp_mb(); /* rcu_sched_qs_mask before cond_resched_completed. */ + if (ACCESS_ONCE(rdp->mynode->completed) != + ACCESS_ONCE(rdp->cond_resched_completed)) + continue; + + /* + * Pretend to be momentarily idle for the quiescent state. + * This allows the grace-period kthread to record the + * quiescent state, with no need for this CPU to do anything + * further. + */ + rdtp = this_cpu_ptr(&rcu_dynticks); + smp_mb__before_atomic(); /* Earlier stuff before QS. */ + atomic_add(2, &rdtp->dynticks); /* QS. */ + smp_mb__after_atomic(); /* Later stuff after QS. */ + break; + } + local_irq_restore(flags); +} + +/* + * Note a context switch. This is a quiescent state for RCU-sched, + * and requires special handling for preemptible RCU. + * The caller must have disabled preemption. + */ +void rcu_note_context_switch(void) +{ + trace_rcu_utilization(TPS("Start context switch")); + rcu_sched_qs(); + rcu_preempt_note_context_switch(); + if (unlikely(raw_cpu_read(rcu_sched_qs_mask))) + rcu_momentary_dyntick_idle(); + trace_rcu_utilization(TPS("End context switch")); +} +EXPORT_SYMBOL_GPL(rcu_note_context_switch); + +/* + * Register a quiescent state for all RCU flavors. If there is an + * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight + * dyntick-idle quiescent state visible to other CPUs (but only for those + * RCU flavors in desperate need of a quiescent state, which will normally + * be none of them). Either way, do a lightweight quiescent state for + * all RCU flavors. + */ +void rcu_all_qs(void) +{ + if (unlikely(raw_cpu_read(rcu_sched_qs_mask))) + rcu_momentary_dyntick_idle(); + this_cpu_inc(rcu_qs_ctr); +} +EXPORT_SYMBOL_GPL(rcu_all_qs); + +static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */ +static long qhimark = 10000; /* If this many pending, ignore blimit. */ +static long qlowmark = 100; /* Once only this many pending, use blimit. */ + +module_param(blimit, long, 0444); +module_param(qhimark, long, 0444); +module_param(qlowmark, long, 0444); + +static ulong jiffies_till_first_fqs = ULONG_MAX; +static ulong jiffies_till_next_fqs = ULONG_MAX; + +module_param(jiffies_till_first_fqs, ulong, 0644); +module_param(jiffies_till_next_fqs, ulong, 0644); + +/* + * How long the grace period must be before we start recruiting + * quiescent-state help from rcu_note_context_switch(). + */ +static ulong jiffies_till_sched_qs = HZ / 20; +module_param(jiffies_till_sched_qs, ulong, 0644); + +static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp); +static void force_qs_rnp(struct rcu_state *rsp, + int (*f)(struct rcu_data *rsp, bool *isidle, + unsigned long *maxj), + bool *isidle, unsigned long *maxj); +static void force_quiescent_state(struct rcu_state *rsp); +static int rcu_pending(void); + +/* + * Return the number of RCU batches started thus far for debug & stats. + */ +unsigned long rcu_batches_started(void) +{ + return rcu_state_p->gpnum; +} +EXPORT_SYMBOL_GPL(rcu_batches_started); + +/* + * Return the number of RCU-sched batches started thus far for debug & stats. + */ +unsigned long rcu_batches_started_sched(void) +{ + return rcu_sched_state.gpnum; +} +EXPORT_SYMBOL_GPL(rcu_batches_started_sched); + +/* + * Return the number of RCU BH batches started thus far for debug & stats. + */ +unsigned long rcu_batches_started_bh(void) +{ + return rcu_bh_state.gpnum; +} +EXPORT_SYMBOL_GPL(rcu_batches_started_bh); + +/* + * Return the number of RCU batches completed thus far for debug & stats. + */ +unsigned long rcu_batches_completed(void) +{ + return rcu_state_p->completed; +} +EXPORT_SYMBOL_GPL(rcu_batches_completed); + +/* + * Return the number of RCU-sched batches completed thus far for debug & stats. + */ +unsigned long rcu_batches_completed_sched(void) +{ + return rcu_sched_state.completed; +} +EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); + +/* + * Return the number of RCU BH batches completed thus far for debug & stats. + */ +unsigned long rcu_batches_completed_bh(void) +{ + return rcu_bh_state.completed; +} +EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); + +/* + * Force a quiescent state. + */ +void rcu_force_quiescent_state(void) +{ + force_quiescent_state(rcu_state_p); +} +EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); + +/* + * Force a quiescent state for RCU BH. + */ +void rcu_bh_force_quiescent_state(void) +{ + force_quiescent_state(&rcu_bh_state); +} +EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); + +/* + * Force a quiescent state for RCU-sched. + */ +void rcu_sched_force_quiescent_state(void) +{ + force_quiescent_state(&rcu_sched_state); +} +EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); + +/* + * Show the state of the grace-period kthreads. + */ +void show_rcu_gp_kthreads(void) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) { + pr_info("%s: wait state: %d ->state: %#lx\n", + rsp->name, rsp->gp_state, rsp->gp_kthread->state); + /* sched_show_task(rsp->gp_kthread); */ + } +} +EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); + +/* + * Record the number of times rcutorture tests have been initiated and + * terminated. This information allows the debugfs tracing stats to be + * correlated to the rcutorture messages, even when the rcutorture module + * is being repeatedly loaded and unloaded. In other words, we cannot + * store this state in rcutorture itself. + */ +void rcutorture_record_test_transition(void) +{ + rcutorture_testseq++; + rcutorture_vernum = 0; +} +EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); + +/* + * Send along grace-period-related data for rcutorture diagnostics. + */ +void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, + unsigned long *gpnum, unsigned long *completed) +{ + struct rcu_state *rsp = NULL; + + switch (test_type) { + case RCU_FLAVOR: + rsp = rcu_state_p; + break; + case RCU_BH_FLAVOR: + rsp = &rcu_bh_state; + break; + case RCU_SCHED_FLAVOR: + rsp = &rcu_sched_state; + break; + default: + break; + } + if (rsp != NULL) { + *flags = ACCESS_ONCE(rsp->gp_flags); + *gpnum = ACCESS_ONCE(rsp->gpnum); + *completed = ACCESS_ONCE(rsp->completed); + return; + } + *flags = 0; + *gpnum = 0; + *completed = 0; +} +EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); + +/* + * Record the number of writer passes through the current rcutorture test. + * This is also used to correlate debugfs tracing stats with the rcutorture + * messages. + */ +void rcutorture_record_progress(unsigned long vernum) +{ + rcutorture_vernum++; +} +EXPORT_SYMBOL_GPL(rcutorture_record_progress); + +/* + * Does the CPU have callbacks ready to be invoked? + */ +static int +cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) +{ + return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] && + rdp->nxttail[RCU_DONE_TAIL] != NULL; +} + +/* + * Return the root node of the specified rcu_state structure. + */ +static struct rcu_node *rcu_get_root(struct rcu_state *rsp) +{ + return &rsp->node[0]; +} + +/* + * Is there any need for future grace periods? + * Interrupts must be disabled. If the caller does not hold the root + * rnp_node structure's ->lock, the results are advisory only. + */ +static int rcu_future_needs_gp(struct rcu_state *rsp) +{ + struct rcu_node *rnp = rcu_get_root(rsp); + int idx = (ACCESS_ONCE(rnp->completed) + 1) & 0x1; + int *fp = &rnp->need_future_gp[idx]; + + return ACCESS_ONCE(*fp); +} + +/* + * Does the current CPU require a not-yet-started grace period? + * The caller must have disabled interrupts to prevent races with + * normal callback registry. + */ +static int +cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) +{ + int i; + + if (rcu_gp_in_progress(rsp)) + return 0; /* No, a grace period is already in progress. */ + if (rcu_future_needs_gp(rsp)) + return 1; /* Yes, a no-CBs CPU needs one. */ + if (!rdp->nxttail[RCU_NEXT_TAIL]) + return 0; /* No, this is a no-CBs (or offline) CPU. */ + if (*rdp->nxttail[RCU_NEXT_READY_TAIL]) + return 1; /* Yes, this CPU has newly registered callbacks. */ + for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) + if (rdp->nxttail[i - 1] != rdp->nxttail[i] && + ULONG_CMP_LT(ACCESS_ONCE(rsp->completed), + rdp->nxtcompleted[i])) + return 1; /* Yes, CBs for future grace period. */ + return 0; /* No grace period needed. */ +} + +/* + * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state + * + * If the new value of the ->dynticks_nesting counter now is zero, + * we really have entered idle, and must do the appropriate accounting. + * The caller must have disabled interrupts. + */ +static void rcu_eqs_enter_common(long long oldval, bool user) +{ + struct rcu_state *rsp; + struct rcu_data *rdp; + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting); + if (!user && !is_idle_task(current)) { + struct task_struct *idle __maybe_unused = + idle_task(smp_processor_id()); + + trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0); + ftrace_dump(DUMP_ORIG); + WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", + current->pid, current->comm, + idle->pid, idle->comm); /* must be idle task! */ + } + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + do_nocb_deferred_wakeup(rdp); + } + rcu_prepare_for_idle(); + /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ + smp_mb__before_atomic(); /* See above. */ + atomic_inc(&rdtp->dynticks); + smp_mb__after_atomic(); /* Force ordering with next sojourn. */ + WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); + rcu_dynticks_task_enter(); + + /* + * It is illegal to enter an extended quiescent state while + * in an RCU read-side critical section. + */ + rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), + "Illegal idle entry in RCU read-side critical section."); + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), + "Illegal idle entry in RCU-bh read-side critical section."); + rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), + "Illegal idle entry in RCU-sched read-side critical section."); +} + +/* + * Enter an RCU extended quiescent state, which can be either the + * idle loop or adaptive-tickless usermode execution. + */ +static void rcu_eqs_enter(bool user) +{ + long long oldval; + struct rcu_dynticks *rdtp; + + rdtp = this_cpu_ptr(&rcu_dynticks); + oldval = rdtp->dynticks_nesting; + WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0); + if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) { + rdtp->dynticks_nesting = 0; + rcu_eqs_enter_common(oldval, user); + } else { + rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE; + } +} + +/** + * rcu_idle_enter - inform RCU that current CPU is entering idle + * + * Enter idle mode, in other words, -leave- the mode in which RCU + * read-side critical sections can occur. (Though RCU read-side + * critical sections can occur in irq handlers in idle, a possibility + * handled by irq_enter() and irq_exit().) + * + * We crowbar the ->dynticks_nesting field to zero to allow for + * the possibility of usermode upcalls having messed up our count + * of interrupt nesting level during the prior busy period. + */ +void rcu_idle_enter(void) +{ + unsigned long flags; + + local_irq_save(flags); + rcu_eqs_enter(false); + rcu_sysidle_enter(0); + local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(rcu_idle_enter); + +#ifdef CONFIG_RCU_USER_QS +/** + * rcu_user_enter - inform RCU that we are resuming userspace. + * + * Enter RCU idle mode right before resuming userspace. No use of RCU + * is permitted between this call and rcu_user_exit(). This way the + * CPU doesn't need to maintain the tick for RCU maintenance purposes + * when the CPU runs in userspace. + */ +void rcu_user_enter(void) +{ + rcu_eqs_enter(1); +} +#endif /* CONFIG_RCU_USER_QS */ + +/** + * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle + * + * Exit from an interrupt handler, which might possibly result in entering + * idle mode, in other words, leaving the mode in which read-side critical + * sections can occur. + * + * This code assumes that the idle loop never does anything that might + * result in unbalanced calls to irq_enter() and irq_exit(). If your + * architecture violates this assumption, RCU will give you what you + * deserve, good and hard. But very infrequently and irreproducibly. + * + * Use things like work queues to work around this limitation. + * + * You have been warned. + */ +void rcu_irq_exit(void) +{ + unsigned long flags; + long long oldval; + struct rcu_dynticks *rdtp; + + local_irq_save(flags); + rdtp = this_cpu_ptr(&rcu_dynticks); + oldval = rdtp->dynticks_nesting; + rdtp->dynticks_nesting--; + WARN_ON_ONCE(rdtp->dynticks_nesting < 0); + if (rdtp->dynticks_nesting) + trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting); + else + rcu_eqs_enter_common(oldval, true); + rcu_sysidle_enter(1); + local_irq_restore(flags); +} + +/* + * rcu_eqs_exit_common - current CPU moving away from extended quiescent state + * + * If the new value of the ->dynticks_nesting counter was previously zero, + * we really have exited idle, and must do the appropriate accounting. + * The caller must have disabled interrupts. + */ +static void rcu_eqs_exit_common(long long oldval, int user) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + rcu_dynticks_task_exit(); + smp_mb__before_atomic(); /* Force ordering w/previous sojourn. */ + atomic_inc(&rdtp->dynticks); + /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ + smp_mb__after_atomic(); /* See above. */ + WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); + rcu_cleanup_after_idle(); + trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting); + if (!user && !is_idle_task(current)) { + struct task_struct *idle __maybe_unused = + idle_task(smp_processor_id()); + + trace_rcu_dyntick(TPS("Error on exit: not idle task"), + oldval, rdtp->dynticks_nesting); + ftrace_dump(DUMP_ORIG); + WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", + current->pid, current->comm, + idle->pid, idle->comm); /* must be idle task! */ + } +} + +/* + * Exit an RCU extended quiescent state, which can be either the + * idle loop or adaptive-tickless usermode execution. + */ +static void rcu_eqs_exit(bool user) +{ + struct rcu_dynticks *rdtp; + long long oldval; + + rdtp = this_cpu_ptr(&rcu_dynticks); + oldval = rdtp->dynticks_nesting; + WARN_ON_ONCE(oldval < 0); + if (oldval & DYNTICK_TASK_NEST_MASK) { + rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE; + } else { + rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; + rcu_eqs_exit_common(oldval, user); + } +} + +/** + * rcu_idle_exit - inform RCU that current CPU is leaving idle + * + * Exit idle mode, in other words, -enter- the mode in which RCU + * read-side critical sections can occur. + * + * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to + * allow for the possibility of usermode upcalls messing up our count + * of interrupt nesting level during the busy period that is just + * now starting. + */ +void rcu_idle_exit(void) +{ + unsigned long flags; + + local_irq_save(flags); + rcu_eqs_exit(false); + rcu_sysidle_exit(0); + local_irq_restore(flags); +} +EXPORT_SYMBOL_GPL(rcu_idle_exit); + +#ifdef CONFIG_RCU_USER_QS +/** + * rcu_user_exit - inform RCU that we are exiting userspace. + * + * Exit RCU idle mode while entering the kernel because it can + * run a RCU read side critical section anytime. + */ +void rcu_user_exit(void) +{ + rcu_eqs_exit(1); +} +#endif /* CONFIG_RCU_USER_QS */ + +/** + * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle + * + * Enter an interrupt handler, which might possibly result in exiting + * idle mode, in other words, entering the mode in which read-side critical + * sections can occur. + * + * Note that the Linux kernel is fully capable of entering an interrupt + * handler that it never exits, for example when doing upcalls to + * user mode! This code assumes that the idle loop never does upcalls to + * user mode. If your architecture does do upcalls from the idle loop (or + * does anything else that results in unbalanced calls to the irq_enter() + * and irq_exit() functions), RCU will give you what you deserve, good + * and hard. But very infrequently and irreproducibly. + * + * Use things like work queues to work around this limitation. + * + * You have been warned. + */ +void rcu_irq_enter(void) +{ + unsigned long flags; + struct rcu_dynticks *rdtp; + long long oldval; + + local_irq_save(flags); + rdtp = this_cpu_ptr(&rcu_dynticks); + oldval = rdtp->dynticks_nesting; + rdtp->dynticks_nesting++; + WARN_ON_ONCE(rdtp->dynticks_nesting == 0); + if (oldval) + trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting); + else + rcu_eqs_exit_common(oldval, true); + rcu_sysidle_exit(1); + local_irq_restore(flags); +} + +/** + * rcu_nmi_enter - inform RCU of entry to NMI context + * + * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and + * rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know + * that the CPU is active. This implementation permits nested NMIs, as + * long as the nesting level does not overflow an int. (You will probably + * run out of stack space first.) + */ +void rcu_nmi_enter(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + int incby = 2; + + /* Complain about underflow. */ + WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0); + + /* + * If idle from RCU viewpoint, atomically increment ->dynticks + * to mark non-idle and increment ->dynticks_nmi_nesting by one. + * Otherwise, increment ->dynticks_nmi_nesting by two. This means + * if ->dynticks_nmi_nesting is equal to one, we are guaranteed + * to be in the outermost NMI handler that interrupted an RCU-idle + * period (observation due to Andy Lutomirski). + */ + if (!(atomic_read(&rdtp->dynticks) & 0x1)) { + smp_mb__before_atomic(); /* Force delay from prior write. */ + atomic_inc(&rdtp->dynticks); + /* atomic_inc() before later RCU read-side crit sects */ + smp_mb__after_atomic(); /* See above. */ + WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); + incby = 1; + } + rdtp->dynticks_nmi_nesting += incby; + barrier(); +} + +/** + * rcu_nmi_exit - inform RCU of exit from NMI context + * + * If we are returning from the outermost NMI handler that interrupted an + * RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting + * to let the RCU grace-period handling know that the CPU is back to + * being RCU-idle. + */ +void rcu_nmi_exit(void) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + /* + * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks. + * (We are exiting an NMI handler, so RCU better be paying attention + * to us!) + */ + WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0); + WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1)); + + /* + * If the nesting level is not 1, the CPU wasn't RCU-idle, so + * leave it in non-RCU-idle state. + */ + if (rdtp->dynticks_nmi_nesting != 1) { + rdtp->dynticks_nmi_nesting -= 2; + return; + } + + /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ + rdtp->dynticks_nmi_nesting = 0; + /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */ + smp_mb__before_atomic(); /* See above. */ + atomic_inc(&rdtp->dynticks); + smp_mb__after_atomic(); /* Force delay to next write. */ + WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1); +} + +/** + * __rcu_is_watching - are RCU read-side critical sections safe? + * + * Return true if RCU is watching the running CPU, which means that + * this CPU can safely enter RCU read-side critical sections. Unlike + * rcu_is_watching(), the caller of __rcu_is_watching() must have at + * least disabled preemption. + */ +bool notrace __rcu_is_watching(void) +{ + return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1; +} + +/** + * rcu_is_watching - see if RCU thinks that the current CPU is idle + * + * If the current CPU is in its idle loop and is neither in an interrupt + * or NMI handler, return true. + */ +bool notrace rcu_is_watching(void) +{ + bool ret; + + preempt_disable(); + ret = __rcu_is_watching(); + preempt_enable(); + return ret; +} +EXPORT_SYMBOL_GPL(rcu_is_watching); + +#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) + +/* + * Is the current CPU online? Disable preemption to avoid false positives + * that could otherwise happen due to the current CPU number being sampled, + * this task being preempted, its old CPU being taken offline, resuming + * on some other CPU, then determining that its old CPU is now offline. + * It is OK to use RCU on an offline processor during initial boot, hence + * the check for rcu_scheduler_fully_active. Note also that it is OK + * for a CPU coming online to use RCU for one jiffy prior to marking itself + * online in the cpu_online_mask. Similarly, it is OK for a CPU going + * offline to continue to use RCU for one jiffy after marking itself + * offline in the cpu_online_mask. This leniency is necessary given the + * non-atomic nature of the online and offline processing, for example, + * the fact that a CPU enters the scheduler after completing the CPU_DYING + * notifiers. + * + * This is also why RCU internally marks CPUs online during the + * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase. + * + * Disable checking if in an NMI handler because we cannot safely report + * errors from NMI handlers anyway. + */ +bool rcu_lockdep_current_cpu_online(void) +{ + struct rcu_data *rdp; + struct rcu_node *rnp; + bool ret; + + if (in_nmi()) + return true; + preempt_disable(); + rdp = this_cpu_ptr(&rcu_sched_data); + rnp = rdp->mynode; + ret = (rdp->grpmask & rcu_rnp_online_cpus(rnp)) || + !rcu_scheduler_fully_active; + preempt_enable(); + return ret; +} +EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); + +#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ + +/** + * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle + * + * If the current CPU is idle or running at a first-level (not nested) + * interrupt from idle, return true. The caller must have at least + * disabled preemption. + */ +static int rcu_is_cpu_rrupt_from_idle(void) +{ + return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 1; +} + +/* + * Snapshot the specified CPU's dynticks counter so that we can later + * credit them with an implicit quiescent state. Return 1 if this CPU + * is in dynticks idle mode, which is an extended quiescent state. + */ +static int dyntick_save_progress_counter(struct rcu_data *rdp, + bool *isidle, unsigned long *maxj) +{ + rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); + rcu_sysidle_check_cpu(rdp, isidle, maxj); + if ((rdp->dynticks_snap & 0x1) == 0) { + trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); + return 1; + } else { + if (ULONG_CMP_LT(ACCESS_ONCE(rdp->gpnum) + ULONG_MAX / 4, + rdp->mynode->gpnum)) + ACCESS_ONCE(rdp->gpwrap) = true; + return 0; + } +} + +/* + * Return true if the specified CPU has passed through a quiescent + * state by virtue of being in or having passed through an dynticks + * idle state since the last call to dyntick_save_progress_counter() + * for this same CPU, or by virtue of having been offline. + */ +static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, + bool *isidle, unsigned long *maxj) +{ + unsigned int curr; + int *rcrmp; + unsigned int snap; + + curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); + snap = (unsigned int)rdp->dynticks_snap; + + /* + * If the CPU passed through or entered a dynticks idle phase with + * no active irq/NMI handlers, then we can safely pretend that the CPU + * already acknowledged the request to pass through a quiescent + * state. Either way, that CPU cannot possibly be in an RCU + * read-side critical section that started before the beginning + * of the current RCU grace period. + */ + if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) { + trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); + rdp->dynticks_fqs++; + return 1; + } + + /* + * Check for the CPU being offline, but only if the grace period + * is old enough. We don't need to worry about the CPU changing + * state: If we see it offline even once, it has been through a + * quiescent state. + * + * The reason for insisting that the grace period be at least + * one jiffy old is that CPUs that are not quite online and that + * have just gone offline can still execute RCU read-side critical + * sections. + */ + if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies)) + return 0; /* Grace period is not old enough. */ + barrier(); + if (cpu_is_offline(rdp->cpu)) { + trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl")); + rdp->offline_fqs++; + return 1; + } + + /* + * A CPU running for an extended time within the kernel can + * delay RCU grace periods. When the CPU is in NO_HZ_FULL mode, + * even context-switching back and forth between a pair of + * in-kernel CPU-bound tasks cannot advance grace periods. + * So if the grace period is old enough, make the CPU pay attention. + * Note that the unsynchronized assignments to the per-CPU + * rcu_sched_qs_mask variable are safe. Yes, setting of + * bits can be lost, but they will be set again on the next + * force-quiescent-state pass. So lost bit sets do not result + * in incorrect behavior, merely in a grace period lasting + * a few jiffies longer than it might otherwise. Because + * there are at most four threads involved, and because the + * updates are only once every few jiffies, the probability of + * lossage (and thus of slight grace-period extension) is + * quite low. + * + * Note that if the jiffies_till_sched_qs boot/sysfs parameter + * is set too high, we override with half of the RCU CPU stall + * warning delay. + */ + rcrmp = &per_cpu(rcu_sched_qs_mask, rdp->cpu); + if (ULONG_CMP_GE(jiffies, + rdp->rsp->gp_start + jiffies_till_sched_qs) || + ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) { + if (!(ACCESS_ONCE(*rcrmp) & rdp->rsp->flavor_mask)) { + ACCESS_ONCE(rdp->cond_resched_completed) = + ACCESS_ONCE(rdp->mynode->completed); + smp_mb(); /* ->cond_resched_completed before *rcrmp. */ + ACCESS_ONCE(*rcrmp) = + ACCESS_ONCE(*rcrmp) + rdp->rsp->flavor_mask; + resched_cpu(rdp->cpu); /* Force CPU into scheduler. */ + rdp->rsp->jiffies_resched += 5; /* Enable beating. */ + } else if (ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) { + /* Time to beat on that CPU again! */ + resched_cpu(rdp->cpu); /* Force CPU into scheduler. */ + rdp->rsp->jiffies_resched += 5; /* Re-enable beating. */ + } + } + + return 0; +} + +static void record_gp_stall_check_time(struct rcu_state *rsp) +{ + unsigned long j = jiffies; + unsigned long j1; + + rsp->gp_start = j; + smp_wmb(); /* Record start time before stall time. */ + j1 = rcu_jiffies_till_stall_check(); + ACCESS_ONCE(rsp->jiffies_stall) = j + j1; + rsp->jiffies_resched = j + j1 / 2; + rsp->n_force_qs_gpstart = ACCESS_ONCE(rsp->n_force_qs); +} + +/* + * Complain about starvation of grace-period kthread. + */ +static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp) +{ + unsigned long gpa; + unsigned long j; + + j = jiffies; + gpa = ACCESS_ONCE(rsp->gp_activity); + if (j - gpa > 2 * HZ) + pr_err("%s kthread starved for %ld jiffies!\n", + rsp->name, j - gpa); +} + +/* + * Dump stacks of all tasks running on stalled CPUs. + */ +static void rcu_dump_cpu_stacks(struct rcu_state *rsp) +{ + int cpu; + unsigned long flags; + struct rcu_node *rnp; + + rcu_for_each_leaf_node(rsp, rnp) { + raw_spin_lock_irqsave(&rnp->lock, flags); + if (rnp->qsmask != 0) { + for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) + if (rnp->qsmask & (1UL << cpu)) + dump_cpu_task(rnp->grplo + cpu); + } + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } +} + +static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum) +{ + int cpu; + long delta; + unsigned long flags; + unsigned long gpa; + unsigned long j; + int ndetected = 0; + struct rcu_node *rnp = rcu_get_root(rsp); + long totqlen = 0; + + /* Only let one CPU complain about others per time interval. */ + + raw_spin_lock_irqsave(&rnp->lock, flags); + delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall); + if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + ACCESS_ONCE(rsp->jiffies_stall) = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; + raw_spin_unlock_irqrestore(&rnp->lock, flags); + + /* + * OK, time to rat on our buddy... + * See Documentation/RCU/stallwarn.txt for info on how to debug + * RCU CPU stall warnings. + */ + pr_err("INFO: %s detected stalls on CPUs/tasks:", + rsp->name); + print_cpu_stall_info_begin(); + rcu_for_each_leaf_node(rsp, rnp) { + raw_spin_lock_irqsave(&rnp->lock, flags); + ndetected += rcu_print_task_stall(rnp); + if (rnp->qsmask != 0) { + for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) + if (rnp->qsmask & (1UL << cpu)) { + print_cpu_stall_info(rsp, + rnp->grplo + cpu); + ndetected++; + } + } + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } + + print_cpu_stall_info_end(); + for_each_possible_cpu(cpu) + totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; + pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n", + smp_processor_id(), (long)(jiffies - rsp->gp_start), + (long)rsp->gpnum, (long)rsp->completed, totqlen); + if (ndetected) { + rcu_dump_cpu_stacks(rsp); + } else { + if (ACCESS_ONCE(rsp->gpnum) != gpnum || + ACCESS_ONCE(rsp->completed) == gpnum) { + pr_err("INFO: Stall ended before state dump start\n"); + } else { + j = jiffies; + gpa = ACCESS_ONCE(rsp->gp_activity); + pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", + rsp->name, j - gpa, j, gpa, + jiffies_till_next_fqs, + rcu_get_root(rsp)->qsmask); + /* In this case, the current CPU might be at fault. */ + sched_show_task(current); + } + } + + /* Complain about tasks blocking the grace period. */ + rcu_print_detail_task_stall(rsp); + + rcu_check_gp_kthread_starvation(rsp); + + force_quiescent_state(rsp); /* Kick them all. */ +} + +static void print_cpu_stall(struct rcu_state *rsp) +{ + int cpu; + unsigned long flags; + struct rcu_node *rnp = rcu_get_root(rsp); + long totqlen = 0; + + /* + * OK, time to rat on ourselves... + * See Documentation/RCU/stallwarn.txt for info on how to debug + * RCU CPU stall warnings. + */ + pr_err("INFO: %s self-detected stall on CPU", rsp->name); + print_cpu_stall_info_begin(); + print_cpu_stall_info(rsp, smp_processor_id()); + print_cpu_stall_info_end(); + for_each_possible_cpu(cpu) + totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen; + pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n", + jiffies - rsp->gp_start, + (long)rsp->gpnum, (long)rsp->completed, totqlen); + + rcu_check_gp_kthread_starvation(rsp); + + rcu_dump_cpu_stacks(rsp); + + raw_spin_lock_irqsave(&rnp->lock, flags); + if (ULONG_CMP_GE(jiffies, ACCESS_ONCE(rsp->jiffies_stall))) + ACCESS_ONCE(rsp->jiffies_stall) = jiffies + + 3 * rcu_jiffies_till_stall_check() + 3; + raw_spin_unlock_irqrestore(&rnp->lock, flags); + + /* + * Attempt to revive the RCU machinery by forcing a context switch. + * + * A context switch would normally allow the RCU state machine to make + * progress and it could be we're stuck in kernel space without context + * switches for an entirely unreasonable amount of time. + */ + resched_cpu(smp_processor_id()); +} + +static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) +{ + unsigned long completed; + unsigned long gpnum; + unsigned long gps; + unsigned long j; + unsigned long js; + struct rcu_node *rnp; + + if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp)) + return; + j = jiffies; + + /* + * Lots of memory barriers to reject false positives. + * + * The idea is to pick up rsp->gpnum, then rsp->jiffies_stall, + * then rsp->gp_start, and finally rsp->completed. These values + * are updated in the opposite order with memory barriers (or + * equivalent) during grace-period initialization and cleanup. + * Now, a false positive can occur if we get an new value of + * rsp->gp_start and a old value of rsp->jiffies_stall. But given + * the memory barriers, the only way that this can happen is if one + * grace period ends and another starts between these two fetches. + * Detect this by comparing rsp->completed with the previous fetch + * from rsp->gpnum. + * + * Given this check, comparisons of jiffies, rsp->jiffies_stall, + * and rsp->gp_start suffice to forestall false positives. + */ + gpnum = ACCESS_ONCE(rsp->gpnum); + smp_rmb(); /* Pick up ->gpnum first... */ + js = ACCESS_ONCE(rsp->jiffies_stall); + smp_rmb(); /* ...then ->jiffies_stall before the rest... */ + gps = ACCESS_ONCE(rsp->gp_start); + smp_rmb(); /* ...and finally ->gp_start before ->completed. */ + completed = ACCESS_ONCE(rsp->completed); + if (ULONG_CMP_GE(completed, gpnum) || + ULONG_CMP_LT(j, js) || + ULONG_CMP_GE(gps, js)) + return; /* No stall or GP completed since entering function. */ + rnp = rdp->mynode; + if (rcu_gp_in_progress(rsp) && + (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask)) { + + /* We haven't checked in, so go dump stack. */ + print_cpu_stall(rsp); + + } else if (rcu_gp_in_progress(rsp) && + ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) { + + /* They had a few time units to dump stack, so complain. */ + print_other_cpu_stall(rsp, gpnum); + } +} + +/** + * rcu_cpu_stall_reset - prevent further stall warnings in current grace period + * + * Set the stall-warning timeout way off into the future, thus preventing + * any RCU CPU stall-warning messages from appearing in the current set of + * RCU grace periods. + * + * The caller must disable hard irqs. + */ +void rcu_cpu_stall_reset(void) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + ACCESS_ONCE(rsp->jiffies_stall) = jiffies + ULONG_MAX / 2; +} + +/* + * Initialize the specified rcu_data structure's default callback list + * to empty. The default callback list is the one that is not used by + * no-callbacks CPUs. + */ +static void init_default_callback_list(struct rcu_data *rdp) +{ + int i; + + rdp->nxtlist = NULL; + for (i = 0; i < RCU_NEXT_SIZE; i++) + rdp->nxttail[i] = &rdp->nxtlist; +} + +/* + * Initialize the specified rcu_data structure's callback list to empty. + */ +static void init_callback_list(struct rcu_data *rdp) +{ + if (init_nocb_callback_list(rdp)) + return; + init_default_callback_list(rdp); +} + +/* + * Determine the value that ->completed will have at the end of the + * next subsequent grace period. This is used to tag callbacks so that + * a CPU can invoke callbacks in a timely fashion even if that CPU has + * been dyntick-idle for an extended period with callbacks under the + * influence of RCU_FAST_NO_HZ. + * + * The caller must hold rnp->lock with interrupts disabled. + */ +static unsigned long rcu_cbs_completed(struct rcu_state *rsp, + struct rcu_node *rnp) +{ + /* + * If RCU is idle, we just wait for the next grace period. + * But we can only be sure that RCU is idle if we are looking + * at the root rcu_node structure -- otherwise, a new grace + * period might have started, but just not yet gotten around + * to initializing the current non-root rcu_node structure. + */ + if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed) + return rnp->completed + 1; + + /* + * Otherwise, wait for a possible partial grace period and + * then the subsequent full grace period. + */ + return rnp->completed + 2; +} + +/* + * Trace-event helper function for rcu_start_future_gp() and + * rcu_nocb_wait_gp(). + */ +static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, + unsigned long c, const char *s) +{ + trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, + rnp->completed, c, rnp->level, + rnp->grplo, rnp->grphi, s); +} + +/* + * Start some future grace period, as needed to handle newly arrived + * callbacks. The required future grace periods are recorded in each + * rcu_node structure's ->need_future_gp field. Returns true if there + * is reason to awaken the grace-period kthread. + * + * The caller must hold the specified rcu_node structure's ->lock. + */ +static bool __maybe_unused +rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, + unsigned long *c_out) +{ + unsigned long c; + int i; + bool ret = false; + struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); + + /* + * Pick up grace-period number for new callbacks. If this + * grace period is already marked as needed, return to the caller. + */ + c = rcu_cbs_completed(rdp->rsp, rnp); + trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); + if (rnp->need_future_gp[c & 0x1]) { + trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); + goto out; + } + + /* + * If either this rcu_node structure or the root rcu_node structure + * believe that a grace period is in progress, then we must wait + * for the one following, which is in "c". Because our request + * will be noticed at the end of the current grace period, we don't + * need to explicitly start one. We only do the lockless check + * of rnp_root's fields if the current rcu_node structure thinks + * there is no grace period in flight, and because we hold rnp->lock, + * the only possible change is when rnp_root's two fields are + * equal, in which case rnp_root->gpnum might be concurrently + * incremented. But that is OK, as it will just result in our + * doing some extra useless work. + */ + if (rnp->gpnum != rnp->completed || + ACCESS_ONCE(rnp_root->gpnum) != ACCESS_ONCE(rnp_root->completed)) { + rnp->need_future_gp[c & 0x1]++; + trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); + goto out; + } + + /* + * There might be no grace period in progress. If we don't already + * hold it, acquire the root rcu_node structure's lock in order to + * start one (if needed). + */ + if (rnp != rnp_root) { + raw_spin_lock(&rnp_root->lock); + smp_mb__after_unlock_lock(); + } + + /* + * Get a new grace-period number. If there really is no grace + * period in progress, it will be smaller than the one we obtained + * earlier. Adjust callbacks as needed. Note that even no-CBs + * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed. + */ + c = rcu_cbs_completed(rdp->rsp, rnp_root); + for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++) + if (ULONG_CMP_LT(c, rdp->nxtcompleted[i])) + rdp->nxtcompleted[i] = c; + + /* + * If the needed for the required grace period is already + * recorded, trace and leave. + */ + if (rnp_root->need_future_gp[c & 0x1]) { + trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); + goto unlock_out; + } + + /* Record the need for the future grace period. */ + rnp_root->need_future_gp[c & 0x1]++; + + /* If a grace period is not already in progress, start one. */ + if (rnp_root->gpnum != rnp_root->completed) { + trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); + } else { + trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); + ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); + } +unlock_out: + if (rnp != rnp_root) + raw_spin_unlock(&rnp_root->lock); +out: + if (c_out != NULL) + *c_out = c; + return ret; +} + +/* + * Clean up any old requests for the just-ended grace period. Also return + * whether any additional grace periods have been requested. Also invoke + * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads + * waiting for this grace period to complete. + */ +static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) +{ + int c = rnp->completed; + int needmore; + struct rcu_data *rdp = this_cpu_ptr(rsp->rda); + + rcu_nocb_gp_cleanup(rsp, rnp); + rnp->need_future_gp[c & 0x1] = 0; + needmore = rnp->need_future_gp[(c + 1) & 0x1]; + trace_rcu_future_gp(rnp, rdp, c, + needmore ? TPS("CleanupMore") : TPS("Cleanup")); + return needmore; +} + +/* + * Awaken the grace-period kthread for the specified flavor of RCU. + * Don't do a self-awaken, and don't bother awakening when there is + * nothing for the grace-period kthread to do (as in several CPUs + * raced to awaken, and we lost), and finally don't try to awaken + * a kthread that has not yet been created. + */ +static void rcu_gp_kthread_wake(struct rcu_state *rsp) +{ + if (current == rsp->gp_kthread || + !ACCESS_ONCE(rsp->gp_flags) || + !rsp->gp_kthread) + return; + wake_up(&rsp->gp_wq); +} + +/* + * If there is room, assign a ->completed number to any callbacks on + * this CPU that have not already been assigned. Also accelerate any + * callbacks that were previously assigned a ->completed number that has + * since proven to be too conservative, which can happen if callbacks get + * assigned a ->completed number while RCU is idle, but with reference to + * a non-root rcu_node structure. This function is idempotent, so it does + * not hurt to call it repeatedly. Returns an flag saying that we should + * awaken the RCU grace-period kthread. + * + * The caller must hold rnp->lock with interrupts disabled. + */ +static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp) +{ + unsigned long c; + int i; + bool ret; + + /* If the CPU has no callbacks, nothing to do. */ + if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) + return false; + + /* + * Starting from the sublist containing the callbacks most + * recently assigned a ->completed number and working down, find the + * first sublist that is not assignable to an upcoming grace period. + * Such a sublist has something in it (first two tests) and has + * a ->completed number assigned that will complete sooner than + * the ->completed number for newly arrived callbacks (last test). + * + * The key point is that any later sublist can be assigned the + * same ->completed number as the newly arrived callbacks, which + * means that the callbacks in any of these later sublist can be + * grouped into a single sublist, whether or not they have already + * been assigned a ->completed number. + */ + c = rcu_cbs_completed(rsp, rnp); + for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--) + if (rdp->nxttail[i] != rdp->nxttail[i - 1] && + !ULONG_CMP_GE(rdp->nxtcompleted[i], c)) + break; + + /* + * If there are no sublist for unassigned callbacks, leave. + * At the same time, advance "i" one sublist, so that "i" will + * index into the sublist where all the remaining callbacks should + * be grouped into. + */ + if (++i >= RCU_NEXT_TAIL) + return false; + + /* + * Assign all subsequent callbacks' ->completed number to the next + * full grace period and group them all in the sublist initially + * indexed by "i". + */ + for (; i <= RCU_NEXT_TAIL; i++) { + rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL]; + rdp->nxtcompleted[i] = c; + } + /* Record any needed additional grace periods. */ + ret = rcu_start_future_gp(rnp, rdp, NULL); + + /* Trace depending on how much we were able to accelerate. */ + if (!*rdp->nxttail[RCU_WAIT_TAIL]) + trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB")); + else + trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB")); + return ret; +} + +/* + * Move any callbacks whose grace period has completed to the + * RCU_DONE_TAIL sublist, then compact the remaining sublists and + * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL + * sublist. This function is idempotent, so it does not hurt to + * invoke it repeatedly. As long as it is not invoked -too- often... + * Returns true if the RCU grace-period kthread needs to be awakened. + * + * The caller must hold rnp->lock with interrupts disabled. + */ +static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp) +{ + int i, j; + + /* If the CPU has no callbacks, nothing to do. */ + if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL]) + return false; + + /* + * Find all callbacks whose ->completed numbers indicate that they + * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. + */ + for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) { + if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i])) + break; + rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i]; + } + /* Clean up any sublist tail pointers that were misordered above. */ + for (j = RCU_WAIT_TAIL; j < i; j++) + rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL]; + + /* Copy down callbacks to fill in empty sublists. */ + for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) { + if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL]) + break; + rdp->nxttail[j] = rdp->nxttail[i]; + rdp->nxtcompleted[j] = rdp->nxtcompleted[i]; + } + + /* Classify any remaining callbacks. */ + return rcu_accelerate_cbs(rsp, rnp, rdp); +} + +/* + * Update CPU-local rcu_data state to record the beginnings and ends of + * grace periods. The caller must hold the ->lock of the leaf rcu_node + * structure corresponding to the current CPU, and must have irqs disabled. + * Returns true if the grace-period kthread needs to be awakened. + */ +static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp) +{ + bool ret; + + /* Handle the ends of any preceding grace periods first. */ + if (rdp->completed == rnp->completed && + !unlikely(ACCESS_ONCE(rdp->gpwrap))) { + + /* No grace period end, so just accelerate recent callbacks. */ + ret = rcu_accelerate_cbs(rsp, rnp, rdp); + + } else { + + /* Advance callbacks. */ + ret = rcu_advance_cbs(rsp, rnp, rdp); + + /* Remember that we saw this grace-period completion. */ + rdp->completed = rnp->completed; + trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend")); + } + + if (rdp->gpnum != rnp->gpnum || unlikely(ACCESS_ONCE(rdp->gpwrap))) { + /* + * If the current grace period is waiting for this CPU, + * set up to detect a quiescent state, otherwise don't + * go looking for one. + */ + rdp->gpnum = rnp->gpnum; + trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart")); + rdp->passed_quiesce = 0; + rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr); + rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask); + zero_cpu_stall_ticks(rdp); + ACCESS_ONCE(rdp->gpwrap) = false; + } + return ret; +} + +static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) +{ + unsigned long flags; + bool needwake; + struct rcu_node *rnp; + + local_irq_save(flags); + rnp = rdp->mynode; + if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) && + rdp->completed == ACCESS_ONCE(rnp->completed) && + !unlikely(ACCESS_ONCE(rdp->gpwrap))) || /* w/out lock. */ + !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ + local_irq_restore(flags); + return; + } + smp_mb__after_unlock_lock(); + needwake = __note_gp_changes(rsp, rnp, rdp); + raw_spin_unlock_irqrestore(&rnp->lock, flags); + if (needwake) + rcu_gp_kthread_wake(rsp); +} + +/* + * Initialize a new grace period. Return 0 if no grace period required. + */ +static int rcu_gp_init(struct rcu_state *rsp) +{ + unsigned long oldmask; + struct rcu_data *rdp; + struct rcu_node *rnp = rcu_get_root(rsp); + + ACCESS_ONCE(rsp->gp_activity) = jiffies; + raw_spin_lock_irq(&rnp->lock); + smp_mb__after_unlock_lock(); + if (!ACCESS_ONCE(rsp->gp_flags)) { + /* Spurious wakeup, tell caller to go back to sleep. */ + raw_spin_unlock_irq(&rnp->lock); + return 0; + } + ACCESS_ONCE(rsp->gp_flags) = 0; /* Clear all flags: New grace period. */ + + if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) { + /* + * Grace period already in progress, don't start another. + * Not supposed to be able to happen. + */ + raw_spin_unlock_irq(&rnp->lock); + return 0; + } + + /* Advance to a new grace period and initialize state. */ + record_gp_stall_check_time(rsp); + /* Record GP times before starting GP, hence smp_store_release(). */ + smp_store_release(&rsp->gpnum, rsp->gpnum + 1); + trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start")); + raw_spin_unlock_irq(&rnp->lock); + + /* + * Apply per-leaf buffered online and offline operations to the + * rcu_node tree. Note that this new grace period need not wait + * for subsequent online CPUs, and that quiescent-state forcing + * will handle subsequent offline CPUs. + */ + rcu_for_each_leaf_node(rsp, rnp) { + raw_spin_lock_irq(&rnp->lock); + smp_mb__after_unlock_lock(); + if (rnp->qsmaskinit == rnp->qsmaskinitnext && + !rnp->wait_blkd_tasks) { + /* Nothing to do on this leaf rcu_node structure. */ + raw_spin_unlock_irq(&rnp->lock); + continue; + } + + /* Record old state, apply changes to ->qsmaskinit field. */ + oldmask = rnp->qsmaskinit; + rnp->qsmaskinit = rnp->qsmaskinitnext; + + /* If zero-ness of ->qsmaskinit changed, propagate up tree. */ + if (!oldmask != !rnp->qsmaskinit) { + if (!oldmask) /* First online CPU for this rcu_node. */ + rcu_init_new_rnp(rnp); + else if (rcu_preempt_has_tasks(rnp)) /* blocked tasks */ + rnp->wait_blkd_tasks = true; + else /* Last offline CPU and can propagate. */ + rcu_cleanup_dead_rnp(rnp); + } + + /* + * If all waited-on tasks from prior grace period are + * done, and if all this rcu_node structure's CPUs are + * still offline, propagate up the rcu_node tree and + * clear ->wait_blkd_tasks. Otherwise, if one of this + * rcu_node structure's CPUs has since come back online, + * simply clear ->wait_blkd_tasks (but rcu_cleanup_dead_rnp() + * checks for this, so just call it unconditionally). + */ + if (rnp->wait_blkd_tasks && + (!rcu_preempt_has_tasks(rnp) || + rnp->qsmaskinit)) { + rnp->wait_blkd_tasks = false; + rcu_cleanup_dead_rnp(rnp); + } + + raw_spin_unlock_irq(&rnp->lock); + } + + /* + * Set the quiescent-state-needed bits in all the rcu_node + * structures for all currently online CPUs in breadth-first order, + * starting from the root rcu_node structure, relying on the layout + * of the tree within the rsp->node[] array. Note that other CPUs + * will access only the leaves of the hierarchy, thus seeing that no + * grace period is in progress, at least until the corresponding + * leaf node has been initialized. In addition, we have excluded + * CPU-hotplug operations. + * + * The grace period cannot complete until the initialization + * process finishes, because this kthread handles both. + */ + rcu_for_each_node_breadth_first(rsp, rnp) { + raw_spin_lock_irq(&rnp->lock); + smp_mb__after_unlock_lock(); + rdp = this_cpu_ptr(rsp->rda); + rcu_preempt_check_blocked_tasks(rnp); + rnp->qsmask = rnp->qsmaskinit; + ACCESS_ONCE(rnp->gpnum) = rsp->gpnum; + if (WARN_ON_ONCE(rnp->completed != rsp->completed)) + ACCESS_ONCE(rnp->completed) = rsp->completed; + if (rnp == rdp->mynode) + (void)__note_gp_changes(rsp, rnp, rdp); + rcu_preempt_boost_start_gp(rnp); + trace_rcu_grace_period_init(rsp->name, rnp->gpnum, + rnp->level, rnp->grplo, + rnp->grphi, rnp->qsmask); + raw_spin_unlock_irq(&rnp->lock); + cond_resched_rcu_qs(); + ACCESS_ONCE(rsp->gp_activity) = jiffies; + if (gp_init_delay > 0 && + !(rsp->gpnum % (rcu_num_nodes * PER_RCU_NODE_PERIOD))) + schedule_timeout_uninterruptible(gp_init_delay); + } + + return 1; +} + +/* + * Do one round of quiescent-state forcing. + */ +static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in) +{ + int fqs_state = fqs_state_in; + bool isidle = false; + unsigned long maxj; + struct rcu_node *rnp = rcu_get_root(rsp); + + ACCESS_ONCE(rsp->gp_activity) = jiffies; + rsp->n_force_qs++; + if (fqs_state == RCU_SAVE_DYNTICK) { + /* Collect dyntick-idle snapshots. */ + if (is_sysidle_rcu_state(rsp)) { + isidle = true; + maxj = jiffies - ULONG_MAX / 4; + } + force_qs_rnp(rsp, dyntick_save_progress_counter, + &isidle, &maxj); + rcu_sysidle_report_gp(rsp, isidle, maxj); + fqs_state = RCU_FORCE_QS; + } else { + /* Handle dyntick-idle and offline CPUs. */ + isidle = true; + force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj); + } + /* Clear flag to prevent immediate re-entry. */ + if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { + raw_spin_lock_irq(&rnp->lock); + smp_mb__after_unlock_lock(); + ACCESS_ONCE(rsp->gp_flags) = + ACCESS_ONCE(rsp->gp_flags) & ~RCU_GP_FLAG_FQS; + raw_spin_unlock_irq(&rnp->lock); + } + return fqs_state; +} + +/* + * Clean up after the old grace period. + */ +static void rcu_gp_cleanup(struct rcu_state *rsp) +{ + unsigned long gp_duration; + bool needgp = false; + int nocb = 0; + struct rcu_data *rdp; + struct rcu_node *rnp = rcu_get_root(rsp); + + ACCESS_ONCE(rsp->gp_activity) = jiffies; + raw_spin_lock_irq(&rnp->lock); + smp_mb__after_unlock_lock(); + gp_duration = jiffies - rsp->gp_start; + if (gp_duration > rsp->gp_max) + rsp->gp_max = gp_duration; + + /* + * We know the grace period is complete, but to everyone else + * it appears to still be ongoing. But it is also the case + * that to everyone else it looks like there is nothing that + * they can do to advance the grace period. It is therefore + * safe for us to drop the lock in order to mark the grace + * period as completed in all of the rcu_node structures. + */ + raw_spin_unlock_irq(&rnp->lock); + + /* + * Propagate new ->completed value to rcu_node structures so + * that other CPUs don't have to wait until the start of the next + * grace period to process their callbacks. This also avoids + * some nasty RCU grace-period initialization races by forcing + * the end of the current grace period to be completely recorded in + * all of the rcu_node structures before the beginning of the next + * grace period is recorded in any of the rcu_node structures. + */ + rcu_for_each_node_breadth_first(rsp, rnp) { + raw_spin_lock_irq(&rnp->lock); + smp_mb__after_unlock_lock(); + WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); + WARN_ON_ONCE(rnp->qsmask); + ACCESS_ONCE(rnp->completed) = rsp->gpnum; + rdp = this_cpu_ptr(rsp->rda); + if (rnp == rdp->mynode) + needgp = __note_gp_changes(rsp, rnp, rdp) || needgp; + /* smp_mb() provided by prior unlock-lock pair. */ + nocb += rcu_future_gp_cleanup(rsp, rnp); + raw_spin_unlock_irq(&rnp->lock); + cond_resched_rcu_qs(); + ACCESS_ONCE(rsp->gp_activity) = jiffies; + } + rnp = rcu_get_root(rsp); + raw_spin_lock_irq(&rnp->lock); + smp_mb__after_unlock_lock(); /* Order GP before ->completed update. */ + rcu_nocb_gp_set(rnp, nocb); + + /* Declare grace period done. */ + ACCESS_ONCE(rsp->completed) = rsp->gpnum; + trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end")); + rsp->fqs_state = RCU_GP_IDLE; + rdp = this_cpu_ptr(rsp->rda); + /* Advance CBs to reduce false positives below. */ + needgp = rcu_advance_cbs(rsp, rnp, rdp) || needgp; + if (needgp || cpu_needs_another_gp(rsp, rdp)) { + ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT; + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("newreq")); + } + raw_spin_unlock_irq(&rnp->lock); +} + +/* + * Body of kthread that handles grace periods. + */ +static int __noreturn rcu_gp_kthread(void *arg) +{ + int fqs_state; + int gf; + unsigned long j; + int ret; + struct rcu_state *rsp = arg; + struct rcu_node *rnp = rcu_get_root(rsp); + + rcu_bind_gp_kthread(); + for (;;) { + + /* Handle grace-period start. */ + for (;;) { + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("reqwait")); + rsp->gp_state = RCU_GP_WAIT_GPS; + wait_event_interruptible(rsp->gp_wq, + ACCESS_ONCE(rsp->gp_flags) & + RCU_GP_FLAG_INIT); + /* Locking provides needed memory barrier. */ + if (rcu_gp_init(rsp)) + break; + cond_resched_rcu_qs(); + ACCESS_ONCE(rsp->gp_activity) = jiffies; + WARN_ON(signal_pending(current)); + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("reqwaitsig")); + } + + /* Handle quiescent-state forcing. */ + fqs_state = RCU_SAVE_DYNTICK; + j = jiffies_till_first_fqs; + if (j > HZ) { + j = HZ; + jiffies_till_first_fqs = HZ; + } + ret = 0; + for (;;) { + if (!ret) + rsp->jiffies_force_qs = jiffies + j; + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("fqswait")); + rsp->gp_state = RCU_GP_WAIT_FQS; + ret = wait_event_interruptible_timeout(rsp->gp_wq, + ((gf = ACCESS_ONCE(rsp->gp_flags)) & + RCU_GP_FLAG_FQS) || + (!ACCESS_ONCE(rnp->qsmask) && + !rcu_preempt_blocked_readers_cgp(rnp)), + j); + /* Locking provides needed memory barriers. */ + /* If grace period done, leave loop. */ + if (!ACCESS_ONCE(rnp->qsmask) && + !rcu_preempt_blocked_readers_cgp(rnp)) + break; + /* If time for quiescent-state forcing, do it. */ + if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) || + (gf & RCU_GP_FLAG_FQS)) { + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("fqsstart")); + fqs_state = rcu_gp_fqs(rsp, fqs_state); + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("fqsend")); + cond_resched_rcu_qs(); + ACCESS_ONCE(rsp->gp_activity) = jiffies; + } else { + /* Deal with stray signal. */ + cond_resched_rcu_qs(); + ACCESS_ONCE(rsp->gp_activity) = jiffies; + WARN_ON(signal_pending(current)); + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("fqswaitsig")); + } + j = jiffies_till_next_fqs; + if (j > HZ) { + j = HZ; + jiffies_till_next_fqs = HZ; + } else if (j < 1) { + j = 1; + jiffies_till_next_fqs = 1; + } + } + + /* Handle grace-period end. */ + rcu_gp_cleanup(rsp); + } +} + +/* + * Start a new RCU grace period if warranted, re-initializing the hierarchy + * in preparation for detecting the next grace period. The caller must hold + * the root node's ->lock and hard irqs must be disabled. + * + * Note that it is legal for a dying CPU (which is marked as offline) to + * invoke this function. This can happen when the dying CPU reports its + * quiescent state. + * + * Returns true if the grace-period kthread must be awakened. + */ +static bool +rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, + struct rcu_data *rdp) +{ + if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { + /* + * Either we have not yet spawned the grace-period + * task, this CPU does not need another grace period, + * or a grace period is already in progress. + * Either way, don't start a new grace period. + */ + return false; + } + ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT; + trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum), + TPS("newreq")); + + /* + * We can't do wakeups while holding the rnp->lock, as that + * could cause possible deadlocks with the rq->lock. Defer + * the wakeup to our caller. + */ + return true; +} + +/* + * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's + * callbacks. Note that rcu_start_gp_advanced() cannot do this because it + * is invoked indirectly from rcu_advance_cbs(), which would result in + * endless recursion -- or would do so if it wasn't for the self-deadlock + * that is encountered beforehand. + * + * Returns true if the grace-period kthread needs to be awakened. + */ +static bool rcu_start_gp(struct rcu_state *rsp) +{ + struct rcu_data *rdp = this_cpu_ptr(rsp->rda); + struct rcu_node *rnp = rcu_get_root(rsp); + bool ret = false; + + /* + * If there is no grace period in progress right now, any + * callbacks we have up to this point will be satisfied by the + * next grace period. Also, advancing the callbacks reduces the + * probability of false positives from cpu_needs_another_gp() + * resulting in pointless grace periods. So, advance callbacks + * then start the grace period! + */ + ret = rcu_advance_cbs(rsp, rnp, rdp) || ret; + ret = rcu_start_gp_advanced(rsp, rnp, rdp) || ret; + return ret; +} + +/* + * Report a full set of quiescent states to the specified rcu_state + * data structure. This involves cleaning up after the prior grace + * period and letting rcu_start_gp() start up the next grace period + * if one is needed. Note that the caller must hold rnp->lock, which + * is released before return. + */ +static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) + __releases(rcu_get_root(rsp)->lock) +{ + WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); + raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); + rcu_gp_kthread_wake(rsp); +} + +/* + * Similar to rcu_report_qs_rdp(), for which it is a helper function. + * Allows quiescent states for a group of CPUs to be reported at one go + * to the specified rcu_node structure, though all the CPUs in the group + * must be represented by the same rcu_node structure (which need not be a + * leaf rcu_node structure, though it often will be). The gps parameter + * is the grace-period snapshot, which means that the quiescent states + * are valid only if rnp->gpnum is equal to gps. That structure's lock + * must be held upon entry, and it is released before return. + */ +static void +rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, + struct rcu_node *rnp, unsigned long gps, unsigned long flags) + __releases(rnp->lock) +{ + unsigned long oldmask = 0; + struct rcu_node *rnp_c; + + /* Walk up the rcu_node hierarchy. */ + for (;;) { + if (!(rnp->qsmask & mask) || rnp->gpnum != gps) { + + /* + * Our bit has already been cleared, or the + * relevant grace period is already over, so done. + */ + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */ + rnp->qsmask &= ~mask; + trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum, + mask, rnp->qsmask, rnp->level, + rnp->grplo, rnp->grphi, + !!rnp->gp_tasks); + if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { + + /* Other bits still set at this level, so done. */ + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + mask = rnp->grpmask; + if (rnp->parent == NULL) { + + /* No more levels. Exit loop holding root lock. */ + + break; + } + raw_spin_unlock_irqrestore(&rnp->lock, flags); + rnp_c = rnp; + rnp = rnp->parent; + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + oldmask = rnp_c->qsmask; + } + + /* + * Get here if we are the last CPU to pass through a quiescent + * state for this grace period. Invoke rcu_report_qs_rsp() + * to clean up and start the next grace period if one is needed. + */ + rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ +} + +/* + * Record a quiescent state for all tasks that were previously queued + * on the specified rcu_node structure and that were blocking the current + * RCU grace period. The caller must hold the specified rnp->lock with + * irqs disabled, and this lock is released upon return, but irqs remain + * disabled. + */ +static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp, + struct rcu_node *rnp, unsigned long flags) + __releases(rnp->lock) +{ + unsigned long gps; + unsigned long mask; + struct rcu_node *rnp_p; + + if (rcu_state_p == &rcu_sched_state || rsp != rcu_state_p || + rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; /* Still need more quiescent states! */ + } + + rnp_p = rnp->parent; + if (rnp_p == NULL) { + /* + * Only one rcu_node structure in the tree, so don't + * try to report up to its nonexistent parent! + */ + rcu_report_qs_rsp(rsp, flags); + return; + } + + /* Report up the rest of the hierarchy, tracking current ->gpnum. */ + gps = rnp->gpnum; + mask = rnp->grpmask; + raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */ + smp_mb__after_unlock_lock(); + rcu_report_qs_rnp(mask, rsp, rnp_p, gps, flags); +} + +/* + * Record a quiescent state for the specified CPU to that CPU's rcu_data + * structure. This must be either called from the specified CPU, or + * called when the specified CPU is known to be offline (and when it is + * also known that no other CPU is concurrently trying to help the offline + * CPU). The lastcomp argument is used to make sure we are still in the + * grace period of interest. We don't want to end the current grace period + * based on quiescent states detected in an earlier grace period! + */ +static void +rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) +{ + unsigned long flags; + unsigned long mask; + bool needwake; + struct rcu_node *rnp; + + rnp = rdp->mynode; + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + if ((rdp->passed_quiesce == 0 && + rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) || + rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum || + rdp->gpwrap) { + + /* + * The grace period in which this quiescent state was + * recorded has ended, so don't report it upwards. + * We will instead need a new quiescent state that lies + * within the current grace period. + */ + rdp->passed_quiesce = 0; /* need qs for new gp. */ + rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr); + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + mask = rdp->grpmask; + if ((rnp->qsmask & mask) == 0) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } else { + rdp->qs_pending = 0; + + /* + * This GP can't end until cpu checks in, so all of our + * callbacks can be processed during the next GP. + */ + needwake = rcu_accelerate_cbs(rsp, rnp, rdp); + + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); + /* ^^^ Released rnp->lock */ + if (needwake) + rcu_gp_kthread_wake(rsp); + } +} + +/* + * Check to see if there is a new grace period of which this CPU + * is not yet aware, and if so, set up local rcu_data state for it. + * Otherwise, see if this CPU has just passed through its first + * quiescent state for this grace period, and record that fact if so. + */ +static void +rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) +{ + /* Check for grace-period ends and beginnings. */ + note_gp_changes(rsp, rdp); + + /* + * Does this CPU still need to do its part for current grace period? + * If no, return and let the other CPUs do their part as well. + */ + if (!rdp->qs_pending) + return; + + /* + * Was there a quiescent state since the beginning of the grace + * period? If no, then exit and wait for the next call. + */ + if (!rdp->passed_quiesce && + rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) + return; + + /* + * Tell RCU we are done (but rcu_report_qs_rdp() will be the + * judge of that). + */ + rcu_report_qs_rdp(rdp->cpu, rsp, rdp); +} + +#ifdef CONFIG_HOTPLUG_CPU + +/* + * Send the specified CPU's RCU callbacks to the orphanage. The + * specified CPU must be offline, and the caller must hold the + * ->orphan_lock. + */ +static void +rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, + struct rcu_node *rnp, struct rcu_data *rdp) +{ + /* No-CBs CPUs do not have orphanable callbacks. */ + if (rcu_is_nocb_cpu(rdp->cpu)) + return; + + /* + * Orphan the callbacks. First adjust the counts. This is safe + * because _rcu_barrier() excludes CPU-hotplug operations, so it + * cannot be running now. Thus no memory barrier is required. + */ + if (rdp->nxtlist != NULL) { + rsp->qlen_lazy += rdp->qlen_lazy; + rsp->qlen += rdp->qlen; + rdp->n_cbs_orphaned += rdp->qlen; + rdp->qlen_lazy = 0; + ACCESS_ONCE(rdp->qlen) = 0; + } + + /* + * Next, move those callbacks still needing a grace period to + * the orphanage, where some other CPU will pick them up. + * Some of the callbacks might have gone partway through a grace + * period, but that is too bad. They get to start over because we + * cannot assume that grace periods are synchronized across CPUs. + * We don't bother updating the ->nxttail[] array yet, instead + * we just reset the whole thing later on. + */ + if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) { + *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL]; + rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL]; + *rdp->nxttail[RCU_DONE_TAIL] = NULL; + } + + /* + * Then move the ready-to-invoke callbacks to the orphanage, + * where some other CPU will pick them up. These will not be + * required to pass though another grace period: They are done. + */ + if (rdp->nxtlist != NULL) { + *rsp->orphan_donetail = rdp->nxtlist; + rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL]; + } + + /* + * Finally, initialize the rcu_data structure's list to empty and + * disallow further callbacks on this CPU. + */ + init_callback_list(rdp); + rdp->nxttail[RCU_NEXT_TAIL] = NULL; +} + +/* + * Adopt the RCU callbacks from the specified rcu_state structure's + * orphanage. The caller must hold the ->orphan_lock. + */ +static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags) +{ + int i; + struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); + + /* No-CBs CPUs are handled specially. */ + if (rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags)) + return; + + /* Do the accounting first. */ + rdp->qlen_lazy += rsp->qlen_lazy; + rdp->qlen += rsp->qlen; + rdp->n_cbs_adopted += rsp->qlen; + if (rsp->qlen_lazy != rsp->qlen) + rcu_idle_count_callbacks_posted(); + rsp->qlen_lazy = 0; + rsp->qlen = 0; + + /* + * We do not need a memory barrier here because the only way we + * can get here if there is an rcu_barrier() in flight is if + * we are the task doing the rcu_barrier(). + */ + + /* First adopt the ready-to-invoke callbacks. */ + if (rsp->orphan_donelist != NULL) { + *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL]; + *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist; + for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--) + if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) + rdp->nxttail[i] = rsp->orphan_donetail; + rsp->orphan_donelist = NULL; + rsp->orphan_donetail = &rsp->orphan_donelist; + } + + /* And then adopt the callbacks that still need a grace period. */ + if (rsp->orphan_nxtlist != NULL) { + *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist; + rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail; + rsp->orphan_nxtlist = NULL; + rsp->orphan_nxttail = &rsp->orphan_nxtlist; + } +} + +/* + * Trace the fact that this CPU is going offline. + */ +static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) +{ + RCU_TRACE(unsigned long mask); + RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda)); + RCU_TRACE(struct rcu_node *rnp = rdp->mynode); + + RCU_TRACE(mask = rdp->grpmask); + trace_rcu_grace_period(rsp->name, + rnp->gpnum + 1 - !!(rnp->qsmask & mask), + TPS("cpuofl")); +} + +/* + * All CPUs for the specified rcu_node structure have gone offline, + * and all tasks that were preempted within an RCU read-side critical + * section while running on one of those CPUs have since exited their RCU + * read-side critical section. Some other CPU is reporting this fact with + * the specified rcu_node structure's ->lock held and interrupts disabled. + * This function therefore goes up the tree of rcu_node structures, + * clearing the corresponding bits in the ->qsmaskinit fields. Note that + * the leaf rcu_node structure's ->qsmaskinit field has already been + * updated + * + * This function does check that the specified rcu_node structure has + * all CPUs offline and no blocked tasks, so it is OK to invoke it + * prematurely. That said, invoking it after the fact will cost you + * a needless lock acquisition. So once it has done its work, don't + * invoke it again. + */ +static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) +{ + long mask; + struct rcu_node *rnp = rnp_leaf; + + if (rnp->qsmaskinit || rcu_preempt_has_tasks(rnp)) + return; + for (;;) { + mask = rnp->grpmask; + rnp = rnp->parent; + if (!rnp) + break; + raw_spin_lock(&rnp->lock); /* irqs already disabled. */ + smp_mb__after_unlock_lock(); /* GP memory ordering. */ + rnp->qsmaskinit &= ~mask; + rnp->qsmask &= ~mask; + if (rnp->qsmaskinit) { + raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + return; + } + raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + } +} + +/* + * The CPU is exiting the idle loop into the arch_cpu_idle_dead() + * function. We now remove it from the rcu_node tree's ->qsmaskinit + * bit masks. + */ +static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp) +{ + unsigned long flags; + unsigned long mask; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ + + /* Remove outgoing CPU from mask in the leaf rcu_node structure. */ + mask = rdp->grpmask; + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); /* Enforce GP memory-order guarantee. */ + rnp->qsmaskinitnext &= ~mask; + raw_spin_unlock_irqrestore(&rnp->lock, flags); +} + +/* + * The CPU has been completely removed, and some other CPU is reporting + * this fact from process context. Do the remainder of the cleanup, + * including orphaning the outgoing CPU's RCU callbacks, and also + * adopting them. There can only be one CPU hotplug operation at a time, + * so no other CPU can be attempting to update rcu_cpu_kthread_task. + */ +static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) +{ + unsigned long flags; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ + + /* Adjust any no-longer-needed kthreads. */ + rcu_boost_kthread_setaffinity(rnp, -1); + + /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */ + raw_spin_lock_irqsave(&rsp->orphan_lock, flags); + rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp); + rcu_adopt_orphan_cbs(rsp, flags); + raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags); + + WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL, + "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n", + cpu, rdp->qlen, rdp->nxtlist); +} + +#else /* #ifdef CONFIG_HOTPLUG_CPU */ + +static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) +{ +} + +static void __maybe_unused rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) +{ +} + +static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp) +{ +} + +static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp) +{ +} + +#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ + +/* + * Invoke any RCU callbacks that have made it to the end of their grace + * period. Thottle as specified by rdp->blimit. + */ +static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) +{ + unsigned long flags; + struct rcu_head *next, *list, **tail; + long bl, count, count_lazy; + int i; + + /* If no callbacks are ready, just return. */ + if (!cpu_has_callbacks_ready_to_invoke(rdp)) { + trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0); + trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist), + need_resched(), is_idle_task(current), + rcu_is_callbacks_kthread()); + return; + } + + /* + * Extract the list of ready callbacks, disabling to prevent + * races with call_rcu() from interrupt handlers. + */ + local_irq_save(flags); + WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); + bl = rdp->blimit; + trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl); + list = rdp->nxtlist; + rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; + *rdp->nxttail[RCU_DONE_TAIL] = NULL; + tail = rdp->nxttail[RCU_DONE_TAIL]; + for (i = RCU_NEXT_SIZE - 1; i >= 0; i--) + if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL]) + rdp->nxttail[i] = &rdp->nxtlist; + local_irq_restore(flags); + + /* Invoke callbacks. */ + count = count_lazy = 0; + while (list) { + next = list->next; + prefetch(next); + debug_rcu_head_unqueue(list); + if (__rcu_reclaim(rsp->name, list)) + count_lazy++; + list = next; + /* Stop only if limit reached and CPU has something to do. */ + if (++count >= bl && + (need_resched() || + (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) + break; + } + + local_irq_save(flags); + trace_rcu_batch_end(rsp->name, count, !!list, need_resched(), + is_idle_task(current), + rcu_is_callbacks_kthread()); + + /* Update count, and requeue any remaining callbacks. */ + if (list != NULL) { + *tail = rdp->nxtlist; + rdp->nxtlist = list; + for (i = 0; i < RCU_NEXT_SIZE; i++) + if (&rdp->nxtlist == rdp->nxttail[i]) + rdp->nxttail[i] = tail; + else + break; + } + smp_mb(); /* List handling before counting for rcu_barrier(). */ + rdp->qlen_lazy -= count_lazy; + ACCESS_ONCE(rdp->qlen) = rdp->qlen - count; + rdp->n_cbs_invoked += count; + + /* Reinstate batch limit if we have worked down the excess. */ + if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) + rdp->blimit = blimit; + + /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ + if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { + rdp->qlen_last_fqs_check = 0; + rdp->n_force_qs_snap = rsp->n_force_qs; + } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) + rdp->qlen_last_fqs_check = rdp->qlen; + WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0)); + + local_irq_restore(flags); + + /* Re-invoke RCU core processing if there are callbacks remaining. */ + if (cpu_has_callbacks_ready_to_invoke(rdp)) + invoke_rcu_core(); +} + +/* + * Check to see if this CPU is in a non-context-switch quiescent state + * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). + * Also schedule RCU core processing. + * + * This function must be called from hardirq context. It is normally + * invoked from the scheduling-clock interrupt. If rcu_pending returns + * false, there is no point in invoking rcu_check_callbacks(). + */ +void rcu_check_callbacks(int user) +{ + trace_rcu_utilization(TPS("Start scheduler-tick")); + increment_cpu_stall_ticks(); + if (user || rcu_is_cpu_rrupt_from_idle()) { + + /* + * Get here if this CPU took its interrupt from user + * mode or from the idle loop, and if this is not a + * nested interrupt. In this case, the CPU is in + * a quiescent state, so note it. + * + * No memory barrier is required here because both + * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local + * variables that other CPUs neither access nor modify, + * at least not while the corresponding CPU is online. + */ + + rcu_sched_qs(); + rcu_bh_qs(); + + } else if (!in_softirq()) { + + /* + * Get here if this CPU did not take its interrupt from + * softirq, in other words, if it is not interrupting + * a rcu_bh read-side critical section. This is an _bh + * critical section, so note it. + */ + + rcu_bh_qs(); + } + rcu_preempt_check_callbacks(); + if (rcu_pending()) + invoke_rcu_core(); + if (user) + rcu_note_voluntary_context_switch(current); + trace_rcu_utilization(TPS("End scheduler-tick")); +} + +/* + * Scan the leaf rcu_node structures, processing dyntick state for any that + * have not yet encountered a quiescent state, using the function specified. + * Also initiate boosting for any threads blocked on the root rcu_node. + * + * The caller must have suppressed start of new grace periods. + */ +static void force_qs_rnp(struct rcu_state *rsp, + int (*f)(struct rcu_data *rsp, bool *isidle, + unsigned long *maxj), + bool *isidle, unsigned long *maxj) +{ + unsigned long bit; + int cpu; + unsigned long flags; + unsigned long mask; + struct rcu_node *rnp; + + rcu_for_each_leaf_node(rsp, rnp) { + cond_resched_rcu_qs(); + mask = 0; + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + if (!rcu_gp_in_progress(rsp)) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + if (rnp->qsmask == 0) { + if (rcu_state_p == &rcu_sched_state || + rsp != rcu_state_p || + rcu_preempt_blocked_readers_cgp(rnp)) { + /* + * No point in scanning bits because they + * are all zero. But we might need to + * priority-boost blocked readers. + */ + rcu_initiate_boost(rnp, flags); + /* rcu_initiate_boost() releases rnp->lock */ + continue; + } + if (rnp->parent && + (rnp->parent->qsmask & rnp->grpmask)) { + /* + * Race between grace-period + * initialization and task exiting RCU + * read-side critical section: Report. + */ + rcu_report_unblock_qs_rnp(rsp, rnp, flags); + /* rcu_report_unblock_qs_rnp() rlses ->lock */ + continue; + } + } + cpu = rnp->grplo; + bit = 1; + for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { + if ((rnp->qsmask & bit) != 0) { + if ((rnp->qsmaskinit & bit) == 0) + *isidle = false; /* Pending hotplug. */ + if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj)) + mask |= bit; + } + } + if (mask != 0) { + /* Idle/offline CPUs, report (releases rnp->lock. */ + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); + } else { + /* Nothing to do here, so just drop the lock. */ + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } + } +} + +/* + * Force quiescent states on reluctant CPUs, and also detect which + * CPUs are in dyntick-idle mode. + */ +static void force_quiescent_state(struct rcu_state *rsp) +{ + unsigned long flags; + bool ret; + struct rcu_node *rnp; + struct rcu_node *rnp_old = NULL; + + /* Funnel through hierarchy to reduce memory contention. */ + rnp = __this_cpu_read(rsp->rda->mynode); + for (; rnp != NULL; rnp = rnp->parent) { + ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || + !raw_spin_trylock(&rnp->fqslock); + if (rnp_old != NULL) + raw_spin_unlock(&rnp_old->fqslock); + if (ret) { + rsp->n_force_qs_lh++; + return; + } + rnp_old = rnp; + } + /* rnp_old == rcu_get_root(rsp), rnp == NULL. */ + + /* Reached the root of the rcu_node tree, acquire lock. */ + raw_spin_lock_irqsave(&rnp_old->lock, flags); + smp_mb__after_unlock_lock(); + raw_spin_unlock(&rnp_old->fqslock); + if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { + rsp->n_force_qs_lh++; + raw_spin_unlock_irqrestore(&rnp_old->lock, flags); + return; /* Someone beat us to it. */ + } + ACCESS_ONCE(rsp->gp_flags) = + ACCESS_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS; + raw_spin_unlock_irqrestore(&rnp_old->lock, flags); + rcu_gp_kthread_wake(rsp); +} + +/* + * This does the RCU core processing work for the specified rcu_state + * and rcu_data structures. This may be called only from the CPU to + * whom the rdp belongs. + */ +static void +__rcu_process_callbacks(struct rcu_state *rsp) +{ + unsigned long flags; + bool needwake; + struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); + + WARN_ON_ONCE(rdp->beenonline == 0); + + /* Update RCU state based on any recent quiescent states. */ + rcu_check_quiescent_state(rsp, rdp); + + /* Does this CPU require a not-yet-started grace period? */ + local_irq_save(flags); + if (cpu_needs_another_gp(rsp, rdp)) { + raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */ + needwake = rcu_start_gp(rsp); + raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags); + if (needwake) + rcu_gp_kthread_wake(rsp); + } else { + local_irq_restore(flags); + } + + /* If there are callbacks ready, invoke them. */ + if (cpu_has_callbacks_ready_to_invoke(rdp)) + invoke_rcu_callbacks(rsp, rdp); + + /* Do any needed deferred wakeups of rcuo kthreads. */ + do_nocb_deferred_wakeup(rdp); +} + +/* + * Do RCU core processing for the current CPU. + */ +static void rcu_process_callbacks(struct softirq_action *unused) +{ + struct rcu_state *rsp; + + if (cpu_is_offline(smp_processor_id())) + return; + trace_rcu_utilization(TPS("Start RCU core")); + for_each_rcu_flavor(rsp) + __rcu_process_callbacks(rsp); + trace_rcu_utilization(TPS("End RCU core")); +} + +/* + * Schedule RCU callback invocation. If the specified type of RCU + * does not support RCU priority boosting, just do a direct call, + * otherwise wake up the per-CPU kernel kthread. Note that because we + * are running on the current CPU with softirqs disabled, the + * rcu_cpu_kthread_task cannot disappear out from under us. + */ +static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) +{ + if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active))) + return; + if (likely(!rsp->boost)) { + rcu_do_batch(rsp, rdp); + return; + } + invoke_rcu_callbacks_kthread(); +} + +static void invoke_rcu_core(void) +{ + if (cpu_online(smp_processor_id())) + raise_softirq(RCU_SOFTIRQ); +} + +/* + * Handle any core-RCU processing required by a call_rcu() invocation. + */ +static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp, + struct rcu_head *head, unsigned long flags) +{ + bool needwake; + + /* + * If called from an extended quiescent state, invoke the RCU + * core in order to force a re-evaluation of RCU's idleness. + */ + if (!rcu_is_watching()) + invoke_rcu_core(); + + /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ + if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) + return; + + /* + * Force the grace period if too many callbacks or too long waiting. + * Enforce hysteresis, and don't invoke force_quiescent_state() + * if some other CPU has recently done so. Also, don't bother + * invoking force_quiescent_state() if the newly enqueued callback + * is the only one waiting for a grace period to complete. + */ + if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { + + /* Are we ignoring a completed grace period? */ + note_gp_changes(rsp, rdp); + + /* Start a new grace period if one not already started. */ + if (!rcu_gp_in_progress(rsp)) { + struct rcu_node *rnp_root = rcu_get_root(rsp); + + raw_spin_lock(&rnp_root->lock); + smp_mb__after_unlock_lock(); + needwake = rcu_start_gp(rsp); + raw_spin_unlock(&rnp_root->lock); + if (needwake) + rcu_gp_kthread_wake(rsp); + } else { + /* Give the grace period a kick. */ + rdp->blimit = LONG_MAX; + if (rsp->n_force_qs == rdp->n_force_qs_snap && + *rdp->nxttail[RCU_DONE_TAIL] != head) + force_quiescent_state(rsp); + rdp->n_force_qs_snap = rsp->n_force_qs; + rdp->qlen_last_fqs_check = rdp->qlen; + } + } +} + +/* + * RCU callback function to leak a callback. + */ +static void rcu_leak_callback(struct rcu_head *rhp) +{ +} + +/* + * Helper function for call_rcu() and friends. The cpu argument will + * normally be -1, indicating "currently running CPU". It may specify + * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier() + * is expected to specify a CPU. + */ +static void +__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), + struct rcu_state *rsp, int cpu, bool lazy) +{ + unsigned long flags; + struct rcu_data *rdp; + + WARN_ON_ONCE((unsigned long)head & 0x1); /* Misaligned rcu_head! */ + if (debug_rcu_head_queue(head)) { + /* Probable double call_rcu(), so leak the callback. */ + ACCESS_ONCE(head->func) = rcu_leak_callback; + WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n"); + return; + } + head->func = func; + head->next = NULL; + + /* + * Opportunistically note grace-period endings and beginnings. + * Note that we might see a beginning right after we see an + * end, but never vice versa, since this CPU has to pass through + * a quiescent state betweentimes. + */ + local_irq_save(flags); + rdp = this_cpu_ptr(rsp->rda); + + /* Add the callback to our list. */ + if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) { + int offline; + + if (cpu != -1) + rdp = per_cpu_ptr(rsp->rda, cpu); + if (likely(rdp->mynode)) { + /* Post-boot, so this should be for a no-CBs CPU. */ + offline = !__call_rcu_nocb(rdp, head, lazy, flags); + WARN_ON_ONCE(offline); + /* Offline CPU, _call_rcu() illegal, leak callback. */ + local_irq_restore(flags); + return; + } + /* + * Very early boot, before rcu_init(). Initialize if needed + * and then drop through to queue the callback. + */ + BUG_ON(cpu != -1); + WARN_ON_ONCE(!rcu_is_watching()); + if (!likely(rdp->nxtlist)) + init_default_callback_list(rdp); + } + ACCESS_ONCE(rdp->qlen) = rdp->qlen + 1; + if (lazy) + rdp->qlen_lazy++; + else + rcu_idle_count_callbacks_posted(); + smp_mb(); /* Count before adding callback for rcu_barrier(). */ + *rdp->nxttail[RCU_NEXT_TAIL] = head; + rdp->nxttail[RCU_NEXT_TAIL] = &head->next; + + if (__is_kfree_rcu_offset((unsigned long)func)) + trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func, + rdp->qlen_lazy, rdp->qlen); + else + trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen); + + /* Go handle any RCU core processing required. */ + __call_rcu_core(rsp, rdp, head, flags); + local_irq_restore(flags); +} + +/* + * Queue an RCU-sched callback for invocation after a grace period. + */ +void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_sched_state, -1, 0); +} +EXPORT_SYMBOL_GPL(call_rcu_sched); + +/* + * Queue an RCU callback for invocation after a quicker grace period. + */ +void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_bh_state, -1, 0); +} +EXPORT_SYMBOL_GPL(call_rcu_bh); + +/* + * Queue an RCU callback for lazy invocation after a grace period. + * This will likely be later named something like "call_rcu_lazy()", + * but this change will require some way of tagging the lazy RCU + * callbacks in the list of pending callbacks. Until then, this + * function may only be called from __kfree_rcu(). + */ +void kfree_call_rcu(struct rcu_head *head, + void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, rcu_state_p, -1, 1); +} +EXPORT_SYMBOL_GPL(kfree_call_rcu); + +/* + * Because a context switch is a grace period for RCU-sched and RCU-bh, + * any blocking grace-period wait automatically implies a grace period + * if there is only one CPU online at any point time during execution + * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to + * occasionally incorrectly indicate that there are multiple CPUs online + * when there was in fact only one the whole time, as this just adds + * some overhead: RCU still operates correctly. + */ +static inline int rcu_blocking_is_gp(void) +{ + int ret; + + might_sleep(); /* Check for RCU read-side critical section. */ + preempt_disable(); + ret = num_online_cpus() <= 1; + preempt_enable(); + return ret; +} + +/** + * synchronize_sched - wait until an rcu-sched grace period has elapsed. + * + * Control will return to the caller some time after a full rcu-sched + * grace period has elapsed, in other words after all currently executing + * rcu-sched read-side critical sections have completed. These read-side + * critical sections are delimited by rcu_read_lock_sched() and + * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), + * local_irq_disable(), and so on may be used in place of + * rcu_read_lock_sched(). + * + * This means that all preempt_disable code sequences, including NMI and + * non-threaded hardware-interrupt handlers, in progress on entry will + * have completed before this primitive returns. However, this does not + * guarantee that softirq handlers will have completed, since in some + * kernels, these handlers can run in process context, and can block. + * + * Note that this guarantee implies further memory-ordering guarantees. + * On systems with more than one CPU, when synchronize_sched() returns, + * each CPU is guaranteed to have executed a full memory barrier since the + * end of its last RCU-sched read-side critical section whose beginning + * preceded the call to synchronize_sched(). In addition, each CPU having + * an RCU read-side critical section that extends beyond the return from + * synchronize_sched() is guaranteed to have executed a full memory barrier + * after the beginning of synchronize_sched() and before the beginning of + * that RCU read-side critical section. Note that these guarantees include + * CPUs that are offline, idle, or executing in user mode, as well as CPUs + * that are executing in the kernel. + * + * Furthermore, if CPU A invoked synchronize_sched(), which returned + * to its caller on CPU B, then both CPU A and CPU B are guaranteed + * to have executed a full memory barrier during the execution of + * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but + * again only if the system has more than one CPU). + * + * This primitive provides the guarantees made by the (now removed) + * synchronize_kernel() API. In contrast, synchronize_rcu() only + * guarantees that rcu_read_lock() sections will have completed. + * In "classic RCU", these two guarantees happen to be one and + * the same, but can differ in realtime RCU implementations. + */ +void synchronize_sched(void) +{ + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && + !lock_is_held(&rcu_lock_map) && + !lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_sched() in RCU-sched read-side critical section"); + if (rcu_blocking_is_gp()) + return; + if (rcu_gp_is_expedited()) + synchronize_sched_expedited(); + else + wait_rcu_gp(call_rcu_sched); +} +EXPORT_SYMBOL_GPL(synchronize_sched); + +/** + * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. + * + * Control will return to the caller some time after a full rcu_bh grace + * period has elapsed, in other words after all currently executing rcu_bh + * read-side critical sections have completed. RCU read-side critical + * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), + * and may be nested. + * + * See the description of synchronize_sched() for more detailed information + * on memory ordering guarantees. + */ +void synchronize_rcu_bh(void) +{ + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && + !lock_is_held(&rcu_lock_map) && + !lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section"); + if (rcu_blocking_is_gp()) + return; + if (rcu_gp_is_expedited()) + synchronize_rcu_bh_expedited(); + else + wait_rcu_gp(call_rcu_bh); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_bh); + +/** + * get_state_synchronize_rcu - Snapshot current RCU state + * + * Returns a cookie that is used by a later call to cond_synchronize_rcu() + * to determine whether or not a full grace period has elapsed in the + * meantime. + */ +unsigned long get_state_synchronize_rcu(void) +{ + /* + * Any prior manipulation of RCU-protected data must happen + * before the load from ->gpnum. + */ + smp_mb(); /* ^^^ */ + + /* + * Make sure this load happens before the purportedly + * time-consuming work between get_state_synchronize_rcu() + * and cond_synchronize_rcu(). + */ + return smp_load_acquire(&rcu_state_p->gpnum); +} +EXPORT_SYMBOL_GPL(get_state_synchronize_rcu); + +/** + * cond_synchronize_rcu - Conditionally wait for an RCU grace period + * + * @oldstate: return value from earlier call to get_state_synchronize_rcu() + * + * If a full RCU grace period has elapsed since the earlier call to + * get_state_synchronize_rcu(), just return. Otherwise, invoke + * synchronize_rcu() to wait for a full grace period. + * + * Yes, this function does not take counter wrap into account. But + * counter wrap is harmless. If the counter wraps, we have waited for + * more than 2 billion grace periods (and way more on a 64-bit system!), + * so waiting for one additional grace period should be just fine. + */ +void cond_synchronize_rcu(unsigned long oldstate) +{ + unsigned long newstate; + + /* + * Ensure that this load happens before any RCU-destructive + * actions the caller might carry out after we return. + */ + newstate = smp_load_acquire(&rcu_state_p->completed); + if (ULONG_CMP_GE(oldstate, newstate)) + synchronize_rcu(); +} +EXPORT_SYMBOL_GPL(cond_synchronize_rcu); + +static int synchronize_sched_expedited_cpu_stop(void *data) +{ + /* + * There must be a full memory barrier on each affected CPU + * between the time that try_stop_cpus() is called and the + * time that it returns. + * + * In the current initial implementation of cpu_stop, the + * above condition is already met when the control reaches + * this point and the following smp_mb() is not strictly + * necessary. Do smp_mb() anyway for documentation and + * robustness against future implementation changes. + */ + smp_mb(); /* See above comment block. */ + return 0; +} + +/** + * synchronize_sched_expedited - Brute-force RCU-sched grace period + * + * Wait for an RCU-sched grace period to elapse, but use a "big hammer" + * approach to force the grace period to end quickly. This consumes + * significant time on all CPUs and is unfriendly to real-time workloads, + * so is thus not recommended for any sort of common-case code. In fact, + * if you are using synchronize_sched_expedited() in a loop, please + * restructure your code to batch your updates, and then use a single + * synchronize_sched() instead. + * + * This implementation can be thought of as an application of ticket + * locking to RCU, with sync_sched_expedited_started and + * sync_sched_expedited_done taking on the roles of the halves + * of the ticket-lock word. Each task atomically increments + * sync_sched_expedited_started upon entry, snapshotting the old value, + * then attempts to stop all the CPUs. If this succeeds, then each + * CPU will have executed a context switch, resulting in an RCU-sched + * grace period. We are then done, so we use atomic_cmpxchg() to + * update sync_sched_expedited_done to match our snapshot -- but + * only if someone else has not already advanced past our snapshot. + * + * On the other hand, if try_stop_cpus() fails, we check the value + * of sync_sched_expedited_done. If it has advanced past our + * initial snapshot, then someone else must have forced a grace period + * some time after we took our snapshot. In this case, our work is + * done for us, and we can simply return. Otherwise, we try again, + * but keep our initial snapshot for purposes of checking for someone + * doing our work for us. + * + * If we fail too many times in a row, we fall back to synchronize_sched(). + */ +void synchronize_sched_expedited(void) +{ + cpumask_var_t cm; + bool cma = false; + int cpu; + long firstsnap, s, snap; + int trycount = 0; + struct rcu_state *rsp = &rcu_sched_state; + + /* + * If we are in danger of counter wrap, just do synchronize_sched(). + * By allowing sync_sched_expedited_started to advance no more than + * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring + * that more than 3.5 billion CPUs would be required to force a + * counter wrap on a 32-bit system. Quite a few more CPUs would of + * course be required on a 64-bit system. + */ + if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start), + (ulong)atomic_long_read(&rsp->expedited_done) + + ULONG_MAX / 8)) { + synchronize_sched(); + atomic_long_inc(&rsp->expedited_wrap); + return; + } + + /* + * Take a ticket. Note that atomic_inc_return() implies a + * full memory barrier. + */ + snap = atomic_long_inc_return(&rsp->expedited_start); + firstsnap = snap; + if (!try_get_online_cpus()) { + /* CPU hotplug operation in flight, fall back to normal GP. */ + wait_rcu_gp(call_rcu_sched); + atomic_long_inc(&rsp->expedited_normal); + return; + } + WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id())); + + /* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */ + cma = zalloc_cpumask_var(&cm, GFP_KERNEL); + if (cma) { + cpumask_copy(cm, cpu_online_mask); + cpumask_clear_cpu(raw_smp_processor_id(), cm); + for_each_cpu(cpu, cm) { + struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); + + if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1)) + cpumask_clear_cpu(cpu, cm); + } + if (cpumask_weight(cm) == 0) + goto all_cpus_idle; + } + + /* + * Each pass through the following loop attempts to force a + * context switch on each CPU. + */ + while (try_stop_cpus(cma ? cm : cpu_online_mask, + synchronize_sched_expedited_cpu_stop, + NULL) == -EAGAIN) { + put_online_cpus(); + atomic_long_inc(&rsp->expedited_tryfail); + + /* Check to see if someone else did our work for us. */ + s = atomic_long_read(&rsp->expedited_done); + if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { + /* ensure test happens before caller kfree */ + smp_mb__before_atomic(); /* ^^^ */ + atomic_long_inc(&rsp->expedited_workdone1); + free_cpumask_var(cm); + return; + } + + /* No joy, try again later. Or just synchronize_sched(). */ + if (trycount++ < 10) { + udelay(trycount * num_online_cpus()); + } else { + wait_rcu_gp(call_rcu_sched); + atomic_long_inc(&rsp->expedited_normal); + free_cpumask_var(cm); + return; + } + + /* Recheck to see if someone else did our work for us. */ + s = atomic_long_read(&rsp->expedited_done); + if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) { + /* ensure test happens before caller kfree */ + smp_mb__before_atomic(); /* ^^^ */ + atomic_long_inc(&rsp->expedited_workdone2); + free_cpumask_var(cm); + return; + } + + /* + * Refetching sync_sched_expedited_started allows later + * callers to piggyback on our grace period. We retry + * after they started, so our grace period works for them, + * and they started after our first try, so their grace + * period works for us. + */ + if (!try_get_online_cpus()) { + /* CPU hotplug operation in flight, use normal GP. */ + wait_rcu_gp(call_rcu_sched); + atomic_long_inc(&rsp->expedited_normal); + free_cpumask_var(cm); + return; + } + snap = atomic_long_read(&rsp->expedited_start); + smp_mb(); /* ensure read is before try_stop_cpus(). */ + } + atomic_long_inc(&rsp->expedited_stoppedcpus); + +all_cpus_idle: + free_cpumask_var(cm); + + /* + * Everyone up to our most recent fetch is covered by our grace + * period. Update the counter, but only if our work is still + * relevant -- which it won't be if someone who started later + * than we did already did their update. + */ + do { + atomic_long_inc(&rsp->expedited_done_tries); + s = atomic_long_read(&rsp->expedited_done); + if (ULONG_CMP_GE((ulong)s, (ulong)snap)) { + /* ensure test happens before caller kfree */ + smp_mb__before_atomic(); /* ^^^ */ + atomic_long_inc(&rsp->expedited_done_lost); + break; + } + } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s); + atomic_long_inc(&rsp->expedited_done_exit); + + put_online_cpus(); +} +EXPORT_SYMBOL_GPL(synchronize_sched_expedited); + +/* + * Check to see if there is any immediate RCU-related work to be done + * by the current CPU, for the specified type of RCU, returning 1 if so. + * The checks are in order of increasing expense: checks that can be + * carried out against CPU-local state are performed first. However, + * we must check for CPU stalls first, else we might not get a chance. + */ +static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) +{ + struct rcu_node *rnp = rdp->mynode; + + rdp->n_rcu_pending++; + + /* Check for CPU stalls, if enabled. */ + check_cpu_stall(rsp, rdp); + + /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */ + if (rcu_nohz_full_cpu(rsp)) + return 0; + + /* Is the RCU core waiting for a quiescent state from this CPU? */ + if (rcu_scheduler_fully_active && + rdp->qs_pending && !rdp->passed_quiesce && + rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) { + rdp->n_rp_qs_pending++; + } else if (rdp->qs_pending && + (rdp->passed_quiesce || + rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) { + rdp->n_rp_report_qs++; + return 1; + } + + /* Does this CPU have callbacks ready to invoke? */ + if (cpu_has_callbacks_ready_to_invoke(rdp)) { + rdp->n_rp_cb_ready++; + return 1; + } + + /* Has RCU gone idle with this CPU needing another grace period? */ + if (cpu_needs_another_gp(rsp, rdp)) { + rdp->n_rp_cpu_needs_gp++; + return 1; + } + + /* Has another RCU grace period completed? */ + if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ + rdp->n_rp_gp_completed++; + return 1; + } + + /* Has a new RCU grace period started? */ + if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum || + unlikely(ACCESS_ONCE(rdp->gpwrap))) { /* outside lock */ + rdp->n_rp_gp_started++; + return 1; + } + + /* Does this CPU need a deferred NOCB wakeup? */ + if (rcu_nocb_need_deferred_wakeup(rdp)) { + rdp->n_rp_nocb_defer_wakeup++; + return 1; + } + + /* nothing to do */ + rdp->n_rp_need_nothing++; + return 0; +} + +/* + * Check to see if there is any immediate RCU-related work to be done + * by the current CPU, returning 1 if so. This function is part of the + * RCU implementation; it is -not- an exported member of the RCU API. + */ +static int rcu_pending(void) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + if (__rcu_pending(rsp, this_cpu_ptr(rsp->rda))) + return 1; + return 0; +} + +/* + * Return true if the specified CPU has any callback. If all_lazy is + * non-NULL, store an indication of whether all callbacks are lazy. + * (If there are no callbacks, all of them are deemed to be lazy.) + */ +static int __maybe_unused rcu_cpu_has_callbacks(bool *all_lazy) +{ + bool al = true; + bool hc = false; + struct rcu_data *rdp; + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + if (!rdp->nxtlist) + continue; + hc = true; + if (rdp->qlen != rdp->qlen_lazy || !all_lazy) { + al = false; + break; + } + } + if (all_lazy) + *all_lazy = al; + return hc; +} + +/* + * Helper function for _rcu_barrier() tracing. If tracing is disabled, + * the compiler is expected to optimize this away. + */ +static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s, + int cpu, unsigned long done) +{ + trace_rcu_barrier(rsp->name, s, cpu, + atomic_read(&rsp->barrier_cpu_count), done); +} + +/* + * RCU callback function for _rcu_barrier(). If we are last, wake + * up the task executing _rcu_barrier(). + */ +static void rcu_barrier_callback(struct rcu_head *rhp) +{ + struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); + struct rcu_state *rsp = rdp->rsp; + + if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { + _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done); + complete(&rsp->barrier_completion); + } else { + _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done); + } +} + +/* + * Called with preemption disabled, and from cross-cpu IRQ context. + */ +static void rcu_barrier_func(void *type) +{ + struct rcu_state *rsp = type; + struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); + + _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done); + atomic_inc(&rsp->barrier_cpu_count); + rsp->call(&rdp->barrier_head, rcu_barrier_callback); +} + +/* + * Orchestrate the specified type of RCU barrier, waiting for all + * RCU callbacks of the specified type to complete. + */ +static void _rcu_barrier(struct rcu_state *rsp) +{ + int cpu; + struct rcu_data *rdp; + unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done); + unsigned long snap_done; + + _rcu_barrier_trace(rsp, "Begin", -1, snap); + + /* Take mutex to serialize concurrent rcu_barrier() requests. */ + mutex_lock(&rsp->barrier_mutex); + + /* + * Ensure that all prior references, including to ->n_barrier_done, + * are ordered before the _rcu_barrier() machinery. + */ + smp_mb(); /* See above block comment. */ + + /* + * Recheck ->n_barrier_done to see if others did our work for us. + * This means checking ->n_barrier_done for an even-to-odd-to-even + * transition. The "if" expression below therefore rounds the old + * value up to the next even number and adds two before comparing. + */ + snap_done = rsp->n_barrier_done; + _rcu_barrier_trace(rsp, "Check", -1, snap_done); + + /* + * If the value in snap is odd, we needed to wait for the current + * rcu_barrier() to complete, then wait for the next one, in other + * words, we need the value of snap_done to be three larger than + * the value of snap. On the other hand, if the value in snap is + * even, we only had to wait for the next rcu_barrier() to complete, + * in other words, we need the value of snap_done to be only two + * greater than the value of snap. The "(snap + 3) & ~0x1" computes + * this for us (thank you, Linus!). + */ + if (ULONG_CMP_GE(snap_done, (snap + 3) & ~0x1)) { + _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done); + smp_mb(); /* caller's subsequent code after above check. */ + mutex_unlock(&rsp->barrier_mutex); + return; + } + + /* + * Increment ->n_barrier_done to avoid duplicate work. Use + * ACCESS_ONCE() to prevent the compiler from speculating + * the increment to precede the early-exit check. + */ + ACCESS_ONCE(rsp->n_barrier_done) = rsp->n_barrier_done + 1; + WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); + _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); + smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ + + /* + * Initialize the count to one rather than to zero in order to + * avoid a too-soon return to zero in case of a short grace period + * (or preemption of this task). Exclude CPU-hotplug operations + * to ensure that no offline CPU has callbacks queued. + */ + init_completion(&rsp->barrier_completion); + atomic_set(&rsp->barrier_cpu_count, 1); + get_online_cpus(); + + /* + * Force each CPU with callbacks to register a new callback. + * When that callback is invoked, we will know that all of the + * corresponding CPU's preceding callbacks have been invoked. + */ + for_each_possible_cpu(cpu) { + if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) + continue; + rdp = per_cpu_ptr(rsp->rda, cpu); + if (rcu_is_nocb_cpu(cpu)) { + if (!rcu_nocb_cpu_needs_barrier(rsp, cpu)) { + _rcu_barrier_trace(rsp, "OfflineNoCB", cpu, + rsp->n_barrier_done); + } else { + _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, + rsp->n_barrier_done); + smp_mb__before_atomic(); + atomic_inc(&rsp->barrier_cpu_count); + __call_rcu(&rdp->barrier_head, + rcu_barrier_callback, rsp, cpu, 0); + } + } else if (ACCESS_ONCE(rdp->qlen)) { + _rcu_barrier_trace(rsp, "OnlineQ", cpu, + rsp->n_barrier_done); + smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); + } else { + _rcu_barrier_trace(rsp, "OnlineNQ", cpu, + rsp->n_barrier_done); + } + } + put_online_cpus(); + + /* + * Now that we have an rcu_barrier_callback() callback on each + * CPU, and thus each counted, remove the initial count. + */ + if (atomic_dec_and_test(&rsp->barrier_cpu_count)) + complete(&rsp->barrier_completion); + + /* Increment ->n_barrier_done to prevent duplicate work. */ + smp_mb(); /* Keep increment after above mechanism. */ + ACCESS_ONCE(rsp->n_barrier_done) = rsp->n_barrier_done + 1; + WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); + _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); + smp_mb(); /* Keep increment before caller's subsequent code. */ + + /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ + wait_for_completion(&rsp->barrier_completion); + + /* Other rcu_barrier() invocations can now safely proceed. */ + mutex_unlock(&rsp->barrier_mutex); +} + +/** + * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. + */ +void rcu_barrier_bh(void) +{ + _rcu_barrier(&rcu_bh_state); +} +EXPORT_SYMBOL_GPL(rcu_barrier_bh); + +/** + * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. + */ +void rcu_barrier_sched(void) +{ + _rcu_barrier(&rcu_sched_state); +} +EXPORT_SYMBOL_GPL(rcu_barrier_sched); + +/* + * Propagate ->qsinitmask bits up the rcu_node tree to account for the + * first CPU in a given leaf rcu_node structure coming online. The caller + * must hold the corresponding leaf rcu_node ->lock with interrrupts + * disabled. + */ +static void rcu_init_new_rnp(struct rcu_node *rnp_leaf) +{ + long mask; + struct rcu_node *rnp = rnp_leaf; + + for (;;) { + mask = rnp->grpmask; + rnp = rnp->parent; + if (rnp == NULL) + return; + raw_spin_lock(&rnp->lock); /* Interrupts already disabled. */ + rnp->qsmaskinit |= mask; + raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */ + } +} + +/* + * Do boot-time initialization of a CPU's per-CPU RCU data. + */ +static void __init +rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) +{ + unsigned long flags; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_node *rnp = rcu_get_root(rsp); + + /* Set up local state, ensuring consistent view of global state. */ + raw_spin_lock_irqsave(&rnp->lock, flags); + rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); + rdp->dynticks = &per_cpu(rcu_dynticks, cpu); + WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE); + WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1); + rdp->cpu = cpu; + rdp->rsp = rsp; + rcu_boot_init_nocb_percpu_data(rdp); + raw_spin_unlock_irqrestore(&rnp->lock, flags); +} + +/* + * Initialize a CPU's per-CPU RCU data. Note that only one online or + * offline event can be happening at a given time. Note also that we + * can accept some slop in the rsp->completed access due to the fact + * that this CPU cannot possibly have any RCU callbacks in flight yet. + */ +static void +rcu_init_percpu_data(int cpu, struct rcu_state *rsp) +{ + unsigned long flags; + unsigned long mask; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_node *rnp = rcu_get_root(rsp); + + /* Set up local state, ensuring consistent view of global state. */ + raw_spin_lock_irqsave(&rnp->lock, flags); + rdp->beenonline = 1; /* We have now been online. */ + rdp->qlen_last_fqs_check = 0; + rdp->n_force_qs_snap = rsp->n_force_qs; + rdp->blimit = blimit; + if (!rdp->nxtlist) + init_callback_list(rdp); /* Re-enable callbacks on this CPU. */ + rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; + rcu_sysidle_init_percpu_data(rdp->dynticks); + atomic_set(&rdp->dynticks->dynticks, + (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1); + raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + + /* + * Add CPU to leaf rcu_node pending-online bitmask. Any needed + * propagation up the rcu_node tree will happen at the beginning + * of the next grace period. + */ + rnp = rdp->mynode; + mask = rdp->grpmask; + raw_spin_lock(&rnp->lock); /* irqs already disabled. */ + smp_mb__after_unlock_lock(); + rnp->qsmaskinitnext |= mask; + rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */ + rdp->completed = rnp->completed; + rdp->passed_quiesce = false; + rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr); + rdp->qs_pending = false; + trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl")); + raw_spin_unlock_irqrestore(&rnp->lock, flags); +} + +static void rcu_prepare_cpu(int cpu) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + rcu_init_percpu_data(cpu, rsp); +} + +/* + * Handle CPU online/offline notification events. + */ +int rcu_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + long cpu = (long)hcpu; + struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); + struct rcu_node *rnp = rdp->mynode; + struct rcu_state *rsp; + + switch (action) { + case CPU_UP_PREPARE: + case CPU_UP_PREPARE_FROZEN: + rcu_prepare_cpu(cpu); + rcu_prepare_kthreads(cpu); + rcu_spawn_all_nocb_kthreads(cpu); + break; + case CPU_ONLINE: + case CPU_DOWN_FAILED: + rcu_boost_kthread_setaffinity(rnp, -1); + break; + case CPU_DOWN_PREPARE: + rcu_boost_kthread_setaffinity(rnp, cpu); + break; + case CPU_DYING: + case CPU_DYING_FROZEN: + for_each_rcu_flavor(rsp) + rcu_cleanup_dying_cpu(rsp); + break; + case CPU_DYING_IDLE: + for_each_rcu_flavor(rsp) { + rcu_cleanup_dying_idle_cpu(cpu, rsp); + } + break; + case CPU_DEAD: + case CPU_DEAD_FROZEN: + case CPU_UP_CANCELED: + case CPU_UP_CANCELED_FROZEN: + for_each_rcu_flavor(rsp) { + rcu_cleanup_dead_cpu(cpu, rsp); + do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu)); + } + break; + default: + break; + } + return NOTIFY_OK; +} + +static int rcu_pm_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + switch (action) { + case PM_HIBERNATION_PREPARE: + case PM_SUSPEND_PREPARE: + if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ + rcu_expedite_gp(); + break; + case PM_POST_HIBERNATION: + case PM_POST_SUSPEND: + if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ + rcu_unexpedite_gp(); + break; + default: + break; + } + return NOTIFY_OK; +} + +/* + * Spawn the kthreads that handle each RCU flavor's grace periods. + */ +static int __init rcu_spawn_gp_kthread(void) +{ + unsigned long flags; + int kthread_prio_in = kthread_prio; + struct rcu_node *rnp; + struct rcu_state *rsp; + struct sched_param sp; + struct task_struct *t; + + /* Force priority into range. */ + if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1) + kthread_prio = 1; + else if (kthread_prio < 0) + kthread_prio = 0; + else if (kthread_prio > 99) + kthread_prio = 99; + if (kthread_prio != kthread_prio_in) + pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n", + kthread_prio, kthread_prio_in); + + rcu_scheduler_fully_active = 1; + for_each_rcu_flavor(rsp) { + t = kthread_create(rcu_gp_kthread, rsp, "%s", rsp->name); + BUG_ON(IS_ERR(t)); + rnp = rcu_get_root(rsp); + raw_spin_lock_irqsave(&rnp->lock, flags); + rsp->gp_kthread = t; + if (kthread_prio) { + sp.sched_priority = kthread_prio; + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); + } + wake_up_process(t); + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } + rcu_spawn_nocb_kthreads(); + rcu_spawn_boost_kthreads(); + return 0; +} +early_initcall(rcu_spawn_gp_kthread); + +/* + * This function is invoked towards the end of the scheduler's initialization + * process. Before this is called, the idle task might contain + * RCU read-side critical sections (during which time, this idle + * task is booting the system). After this function is called, the + * idle tasks are prohibited from containing RCU read-side critical + * sections. This function also enables RCU lockdep checking. + */ +void rcu_scheduler_starting(void) +{ + WARN_ON(num_online_cpus() != 1); + WARN_ON(nr_context_switches() > 0); + rcu_scheduler_active = 1; +} + +/* + * Compute the per-level fanout, either using the exact fanout specified + * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. + */ +static void __init rcu_init_levelspread(struct rcu_state *rsp) +{ + int i; + + if (IS_ENABLED(CONFIG_RCU_FANOUT_EXACT)) { + rsp->levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf; + for (i = rcu_num_lvls - 2; i >= 0; i--) + rsp->levelspread[i] = CONFIG_RCU_FANOUT; + } else { + int ccur; + int cprv; + + cprv = nr_cpu_ids; + for (i = rcu_num_lvls - 1; i >= 0; i--) { + ccur = rsp->levelcnt[i]; + rsp->levelspread[i] = (cprv + ccur - 1) / ccur; + cprv = ccur; + } + } +} + +/* + * Helper function for rcu_init() that initializes one rcu_state structure. + */ +static void __init rcu_init_one(struct rcu_state *rsp, + struct rcu_data __percpu *rda) +{ + static const char * const buf[] = { + "rcu_node_0", + "rcu_node_1", + "rcu_node_2", + "rcu_node_3" }; /* Match MAX_RCU_LVLS */ + static const char * const fqs[] = { + "rcu_node_fqs_0", + "rcu_node_fqs_1", + "rcu_node_fqs_2", + "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ + static u8 fl_mask = 0x1; + int cpustride = 1; + int i; + int j; + struct rcu_node *rnp; + + BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ + + /* Silence gcc 4.8 warning about array index out of range. */ + if (rcu_num_lvls > RCU_NUM_LVLS) + panic("rcu_init_one: rcu_num_lvls overflow"); + + /* Initialize the level-tracking arrays. */ + + for (i = 0; i < rcu_num_lvls; i++) + rsp->levelcnt[i] = num_rcu_lvl[i]; + for (i = 1; i < rcu_num_lvls; i++) + rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; + rcu_init_levelspread(rsp); + rsp->flavor_mask = fl_mask; + fl_mask <<= 1; + + /* Initialize the elements themselves, starting from the leaves. */ + + for (i = rcu_num_lvls - 1; i >= 0; i--) { + cpustride *= rsp->levelspread[i]; + rnp = rsp->level[i]; + for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { + raw_spin_lock_init(&rnp->lock); + lockdep_set_class_and_name(&rnp->lock, + &rcu_node_class[i], buf[i]); + raw_spin_lock_init(&rnp->fqslock); + lockdep_set_class_and_name(&rnp->fqslock, + &rcu_fqs_class[i], fqs[i]); + rnp->gpnum = rsp->gpnum; + rnp->completed = rsp->completed; + rnp->qsmask = 0; + rnp->qsmaskinit = 0; + rnp->grplo = j * cpustride; + rnp->grphi = (j + 1) * cpustride - 1; + if (rnp->grphi >= nr_cpu_ids) + rnp->grphi = nr_cpu_ids - 1; + if (i == 0) { + rnp->grpnum = 0; + rnp->grpmask = 0; + rnp->parent = NULL; + } else { + rnp->grpnum = j % rsp->levelspread[i - 1]; + rnp->grpmask = 1UL << rnp->grpnum; + rnp->parent = rsp->level[i - 1] + + j / rsp->levelspread[i - 1]; + } + rnp->level = i; + INIT_LIST_HEAD(&rnp->blkd_tasks); + rcu_init_one_nocb(rnp); + } + } + + init_waitqueue_head(&rsp->gp_wq); + rnp = rsp->level[rcu_num_lvls - 1]; + for_each_possible_cpu(i) { + while (i > rnp->grphi) + rnp++; + per_cpu_ptr(rsp->rda, i)->mynode = rnp; + rcu_boot_init_percpu_data(i, rsp); + } + list_add(&rsp->flavors, &rcu_struct_flavors); +} + +/* + * Compute the rcu_node tree geometry from kernel parameters. This cannot + * replace the definitions in tree.h because those are needed to size + * the ->node array in the rcu_state structure. + */ +static void __init rcu_init_geometry(void) +{ + ulong d; + int i; + int j; + int n = nr_cpu_ids; + int rcu_capacity[MAX_RCU_LVLS + 1]; + + /* + * Initialize any unspecified boot parameters. + * The default values of jiffies_till_first_fqs and + * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS + * value, which is a function of HZ, then adding one for each + * RCU_JIFFIES_FQS_DIV CPUs that might be on the system. + */ + d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; + if (jiffies_till_first_fqs == ULONG_MAX) + jiffies_till_first_fqs = d; + if (jiffies_till_next_fqs == ULONG_MAX) + jiffies_till_next_fqs = d; + + /* If the compile-time values are accurate, just leave. */ + if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF && + nr_cpu_ids == NR_CPUS) + return; + pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n", + rcu_fanout_leaf, nr_cpu_ids); + + /* + * Compute number of nodes that can be handled an rcu_node tree + * with the given number of levels. Setting rcu_capacity[0] makes + * some of the arithmetic easier. + */ + rcu_capacity[0] = 1; + rcu_capacity[1] = rcu_fanout_leaf; + for (i = 2; i <= MAX_RCU_LVLS; i++) + rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; + + /* + * The boot-time rcu_fanout_leaf parameter is only permitted + * to increase the leaf-level fanout, not decrease it. Of course, + * the leaf-level fanout cannot exceed the number of bits in + * the rcu_node masks. Finally, the tree must be able to accommodate + * the configured number of CPUs. Complain and fall back to the + * compile-time values if these limits are exceeded. + */ + if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || + rcu_fanout_leaf > sizeof(unsigned long) * 8 || + n > rcu_capacity[MAX_RCU_LVLS]) { + WARN_ON(1); + return; + } + + /* Calculate the number of rcu_nodes at each level of the tree. */ + for (i = 1; i <= MAX_RCU_LVLS; i++) + if (n <= rcu_capacity[i]) { + for (j = 0; j <= i; j++) + num_rcu_lvl[j] = + DIV_ROUND_UP(n, rcu_capacity[i - j]); + rcu_num_lvls = i; + for (j = i + 1; j <= MAX_RCU_LVLS; j++) + num_rcu_lvl[j] = 0; + break; + } + + /* Calculate the total number of rcu_node structures. */ + rcu_num_nodes = 0; + for (i = 0; i <= MAX_RCU_LVLS; i++) + rcu_num_nodes += num_rcu_lvl[i]; + rcu_num_nodes -= n; +} + +void __init rcu_init(void) +{ + int cpu; + + rcu_early_boot_tests(); + + rcu_bootup_announce(); + rcu_init_geometry(); + rcu_init_one(&rcu_bh_state, &rcu_bh_data); + rcu_init_one(&rcu_sched_state, &rcu_sched_data); + __rcu_init_preempt(); + open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); + + /* + * We don't need protection against CPU-hotplug here because + * this is called early in boot, before either interrupts + * or the scheduler are operational. + */ + cpu_notifier(rcu_cpu_notify, 0); + pm_notifier(rcu_pm_notify, 0); + for_each_online_cpu(cpu) + rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); +} + +#include "tree_plugin.h" diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h new file mode 100644 index 000000000..a69d3dab2 --- /dev/null +++ b/kernel/rcu/tree.h @@ -0,0 +1,620 @@ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * Internal non-public definitions. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2008 + * + * Author: Ingo Molnar <mingo@elte.hu> + * Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#include <linux/cache.h> +#include <linux/spinlock.h> +#include <linux/threads.h> +#include <linux/cpumask.h> +#include <linux/seqlock.h> + +/* + * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and + * CONFIG_RCU_FANOUT_LEAF. + * In theory, it should be possible to add more levels straightforwardly. + * In practice, this did work well going from three levels to four. + * Of course, your mileage may vary. + */ +#define MAX_RCU_LVLS 4 +#define RCU_FANOUT_1 (CONFIG_RCU_FANOUT_LEAF) +#define RCU_FANOUT_2 (RCU_FANOUT_1 * CONFIG_RCU_FANOUT) +#define RCU_FANOUT_3 (RCU_FANOUT_2 * CONFIG_RCU_FANOUT) +#define RCU_FANOUT_4 (RCU_FANOUT_3 * CONFIG_RCU_FANOUT) + +#if NR_CPUS <= RCU_FANOUT_1 +# define RCU_NUM_LVLS 1 +# define NUM_RCU_LVL_0 1 +# define NUM_RCU_LVL_1 (NR_CPUS) +# define NUM_RCU_LVL_2 0 +# define NUM_RCU_LVL_3 0 +# define NUM_RCU_LVL_4 0 +#elif NR_CPUS <= RCU_FANOUT_2 +# define RCU_NUM_LVLS 2 +# define NUM_RCU_LVL_0 1 +# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) +# define NUM_RCU_LVL_2 (NR_CPUS) +# define NUM_RCU_LVL_3 0 +# define NUM_RCU_LVL_4 0 +#elif NR_CPUS <= RCU_FANOUT_3 +# define RCU_NUM_LVLS 3 +# define NUM_RCU_LVL_0 1 +# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) +# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) +# define NUM_RCU_LVL_3 (NR_CPUS) +# define NUM_RCU_LVL_4 0 +#elif NR_CPUS <= RCU_FANOUT_4 +# define RCU_NUM_LVLS 4 +# define NUM_RCU_LVL_0 1 +# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) +# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) +# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) +# define NUM_RCU_LVL_4 (NR_CPUS) +#else +# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" +#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ + +#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4) +#define NUM_RCU_NODES (RCU_SUM - NR_CPUS) + +extern int rcu_num_lvls; +extern int rcu_num_nodes; + +/* + * Dynticks per-CPU state. + */ +struct rcu_dynticks { + long long dynticks_nesting; /* Track irq/process nesting level. */ + /* Process level is worth LLONG_MAX/2. */ + int dynticks_nmi_nesting; /* Track NMI nesting level. */ + atomic_t dynticks; /* Even value for idle, else odd. */ +#ifdef CONFIG_NO_HZ_FULL_SYSIDLE + long long dynticks_idle_nesting; + /* irq/process nesting level from idle. */ + atomic_t dynticks_idle; /* Even value for idle, else odd. */ + /* "Idle" excludes userspace execution. */ + unsigned long dynticks_idle_jiffies; + /* End of last non-NMI non-idle period. */ +#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ +#ifdef CONFIG_RCU_FAST_NO_HZ + bool all_lazy; /* Are all CPU's CBs lazy? */ + unsigned long nonlazy_posted; + /* # times non-lazy CBs posted to CPU. */ + unsigned long nonlazy_posted_snap; + /* idle-period nonlazy_posted snapshot. */ + unsigned long last_accelerate; + /* Last jiffy CBs were accelerated. */ + unsigned long last_advance_all; + /* Last jiffy CBs were all advanced. */ + int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ +#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ +}; + +/* RCU's kthread states for tracing. */ +#define RCU_KTHREAD_STOPPED 0 +#define RCU_KTHREAD_RUNNING 1 +#define RCU_KTHREAD_WAITING 2 +#define RCU_KTHREAD_OFFCPU 3 +#define RCU_KTHREAD_YIELDING 4 +#define RCU_KTHREAD_MAX 4 + +/* + * Definition for node within the RCU grace-period-detection hierarchy. + */ +struct rcu_node { + raw_spinlock_t lock; /* Root rcu_node's lock protects some */ + /* rcu_state fields as well as following. */ + unsigned long gpnum; /* Current grace period for this node. */ + /* This will either be equal to or one */ + /* behind the root rcu_node's gpnum. */ + unsigned long completed; /* Last GP completed for this node. */ + /* This will either be equal to or one */ + /* behind the root rcu_node's gpnum. */ + unsigned long qsmask; /* CPUs or groups that need to switch in */ + /* order for current grace period to proceed.*/ + /* In leaf rcu_node, each bit corresponds to */ + /* an rcu_data structure, otherwise, each */ + /* bit corresponds to a child rcu_node */ + /* structure. */ + unsigned long expmask; /* Groups that have ->blkd_tasks */ + /* elements that need to drain to allow the */ + /* current expedited grace period to */ + /* complete (only for PREEMPT_RCU). */ + unsigned long qsmaskinit; + /* Per-GP initial value for qsmask & expmask. */ + /* Initialized from ->qsmaskinitnext at the */ + /* beginning of each grace period. */ + unsigned long qsmaskinitnext; + /* Online CPUs for next grace period. */ + unsigned long grpmask; /* Mask to apply to parent qsmask. */ + /* Only one bit will be set in this mask. */ + int grplo; /* lowest-numbered CPU or group here. */ + int grphi; /* highest-numbered CPU or group here. */ + u8 grpnum; /* CPU/group number for next level up. */ + u8 level; /* root is at level 0. */ + bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ + /* exit RCU read-side critical sections */ + /* before propagating offline up the */ + /* rcu_node tree? */ + struct rcu_node *parent; + struct list_head blkd_tasks; + /* Tasks blocked in RCU read-side critical */ + /* section. Tasks are placed at the head */ + /* of this list and age towards the tail. */ + struct list_head *gp_tasks; + /* Pointer to the first task blocking the */ + /* current grace period, or NULL if there */ + /* is no such task. */ + struct list_head *exp_tasks; + /* Pointer to the first task blocking the */ + /* current expedited grace period, or NULL */ + /* if there is no such task. If there */ + /* is no current expedited grace period, */ + /* then there can cannot be any such task. */ +#ifdef CONFIG_RCU_BOOST + struct list_head *boost_tasks; + /* Pointer to first task that needs to be */ + /* priority boosted, or NULL if no priority */ + /* boosting is needed for this rcu_node */ + /* structure. If there are no tasks */ + /* queued on this rcu_node structure that */ + /* are blocking the current grace period, */ + /* there can be no such task. */ + struct rt_mutex boost_mtx; + /* Used only for the priority-boosting */ + /* side effect, not as a lock. */ + unsigned long boost_time; + /* When to start boosting (jiffies). */ + struct task_struct *boost_kthread_task; + /* kthread that takes care of priority */ + /* boosting for this rcu_node structure. */ + unsigned int boost_kthread_status; + /* State of boost_kthread_task for tracing. */ + unsigned long n_tasks_boosted; + /* Total number of tasks boosted. */ + unsigned long n_exp_boosts; + /* Number of tasks boosted for expedited GP. */ + unsigned long n_normal_boosts; + /* Number of tasks boosted for normal GP. */ + unsigned long n_balk_blkd_tasks; + /* Refused to boost: no blocked tasks. */ + unsigned long n_balk_exp_gp_tasks; + /* Refused to boost: nothing blocking GP. */ + unsigned long n_balk_boost_tasks; + /* Refused to boost: already boosting. */ + unsigned long n_balk_notblocked; + /* Refused to boost: RCU RS CS still running. */ + unsigned long n_balk_notyet; + /* Refused to boost: not yet time. */ + unsigned long n_balk_nos; + /* Refused to boost: not sure why, though. */ + /* This can happen due to race conditions. */ +#endif /* #ifdef CONFIG_RCU_BOOST */ +#ifdef CONFIG_RCU_NOCB_CPU + wait_queue_head_t nocb_gp_wq[2]; + /* Place for rcu_nocb_kthread() to wait GP. */ +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ + int need_future_gp[2]; + /* Counts of upcoming no-CB GP requests. */ + raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; +} ____cacheline_internodealigned_in_smp; + +/* + * Do a full breadth-first scan of the rcu_node structures for the + * specified rcu_state structure. + */ +#define rcu_for_each_node_breadth_first(rsp, rnp) \ + for ((rnp) = &(rsp)->node[0]; \ + (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) + +/* + * Do a breadth-first scan of the non-leaf rcu_node structures for the + * specified rcu_state structure. Note that if there is a singleton + * rcu_node tree with but one rcu_node structure, this loop is a no-op. + */ +#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \ + for ((rnp) = &(rsp)->node[0]; \ + (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++) + +/* + * Scan the leaves of the rcu_node hierarchy for the specified rcu_state + * structure. Note that if there is a singleton rcu_node tree with but + * one rcu_node structure, this loop -will- visit the rcu_node structure. + * It is still a leaf node, even if it is also the root node. + */ +#define rcu_for_each_leaf_node(rsp, rnp) \ + for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \ + (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) + +/* Index values for nxttail array in struct rcu_data. */ +#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ +#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ +#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */ +#define RCU_NEXT_TAIL 3 +#define RCU_NEXT_SIZE 4 + +/* Per-CPU data for read-copy update. */ +struct rcu_data { + /* 1) quiescent-state and grace-period handling : */ + unsigned long completed; /* Track rsp->completed gp number */ + /* in order to detect GP end. */ + unsigned long gpnum; /* Highest gp number that this CPU */ + /* is aware of having started. */ + unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */ + /* for rcu_all_qs() invocations. */ + bool passed_quiesce; /* User-mode/idle loop etc. */ + bool qs_pending; /* Core waits for quiesc state. */ + bool beenonline; /* CPU online at least once. */ + bool gpwrap; /* Possible gpnum/completed wrap. */ + struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ + unsigned long grpmask; /* Mask to apply to leaf qsmask. */ +#ifdef CONFIG_RCU_CPU_STALL_INFO + unsigned long ticks_this_gp; /* The number of scheduling-clock */ + /* ticks this CPU has handled */ + /* during and after the last grace */ + /* period it is aware of. */ +#endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ + + /* 2) batch handling */ + /* + * If nxtlist is not NULL, it is partitioned as follows. + * Any of the partitions might be empty, in which case the + * pointer to that partition will be equal to the pointer for + * the following partition. When the list is empty, all of + * the nxttail elements point to the ->nxtlist pointer itself, + * which in that case is NULL. + * + * [nxtlist, *nxttail[RCU_DONE_TAIL]): + * Entries that batch # <= ->completed + * The grace period for these entries has completed, and + * the other grace-period-completed entries may be moved + * here temporarily in rcu_process_callbacks(). + * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): + * Entries that batch # <= ->completed - 1: waiting for current GP + * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): + * Entries known to have arrived before current GP ended + * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]): + * Entries that might have arrived after current GP ended + * Note that the value of *nxttail[RCU_NEXT_TAIL] will + * always be NULL, as this is the end of the list. + */ + struct rcu_head *nxtlist; + struct rcu_head **nxttail[RCU_NEXT_SIZE]; + unsigned long nxtcompleted[RCU_NEXT_SIZE]; + /* grace periods for sublists. */ + long qlen_lazy; /* # of lazy queued callbacks */ + long qlen; /* # of queued callbacks, incl lazy */ + long qlen_last_fqs_check; + /* qlen at last check for QS forcing */ + unsigned long n_cbs_invoked; /* count of RCU cbs invoked. */ + unsigned long n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */ + unsigned long n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */ + unsigned long n_cbs_adopted; /* RCU cbs adopted from dying CPU */ + unsigned long n_force_qs_snap; + /* did other CPU force QS recently? */ + long blimit; /* Upper limit on a processed batch */ + + /* 3) dynticks interface. */ + struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ + int dynticks_snap; /* Per-GP tracking for dynticks. */ + + /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ + unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ + unsigned long offline_fqs; /* Kicked due to being offline. */ + unsigned long cond_resched_completed; + /* Grace period that needs help */ + /* from cond_resched(). */ + + /* 5) __rcu_pending() statistics. */ + unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */ + unsigned long n_rp_qs_pending; + unsigned long n_rp_report_qs; + unsigned long n_rp_cb_ready; + unsigned long n_rp_cpu_needs_gp; + unsigned long n_rp_gp_completed; + unsigned long n_rp_gp_started; + unsigned long n_rp_nocb_defer_wakeup; + unsigned long n_rp_need_nothing; + + /* 6) _rcu_barrier() and OOM callbacks. */ + struct rcu_head barrier_head; +#ifdef CONFIG_RCU_FAST_NO_HZ + struct rcu_head oom_head; +#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ + + /* 7) Callback offloading. */ +#ifdef CONFIG_RCU_NOCB_CPU + struct rcu_head *nocb_head; /* CBs waiting for kthread. */ + struct rcu_head **nocb_tail; + atomic_long_t nocb_q_count; /* # CBs waiting for nocb */ + atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */ + struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */ + struct rcu_head **nocb_follower_tail; + wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */ + struct task_struct *nocb_kthread; + int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ + + /* The following fields are used by the leader, hence own cacheline. */ + struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp; + /* CBs waiting for GP. */ + struct rcu_head **nocb_gp_tail; + bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */ + struct rcu_data *nocb_next_follower; + /* Next follower in wakeup chain. */ + + /* The following fields are used by the follower, hence new cachline. */ + struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp; + /* Leader CPU takes GP-end wakeups. */ +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ + + /* 8) RCU CPU stall data. */ +#ifdef CONFIG_RCU_CPU_STALL_INFO + unsigned int softirq_snap; /* Snapshot of softirq activity. */ +#endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ + + int cpu; + struct rcu_state *rsp; +}; + +/* Values for fqs_state field in struct rcu_state. */ +#define RCU_GP_IDLE 0 /* No grace period in progress. */ +#define RCU_GP_INIT 1 /* Grace period being initialized. */ +#define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */ +#define RCU_FORCE_QS 3 /* Need to force quiescent state. */ +#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK + +/* Values for nocb_defer_wakeup field in struct rcu_data. */ +#define RCU_NOGP_WAKE_NOT 0 +#define RCU_NOGP_WAKE 1 +#define RCU_NOGP_WAKE_FORCE 2 + +#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) + /* For jiffies_till_first_fqs and */ + /* and jiffies_till_next_fqs. */ + +#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ + /* delay between bouts of */ + /* quiescent-state forcing. */ + +#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ + /* at least one scheduling clock */ + /* irq before ratting on them. */ + +#define rcu_wait(cond) \ +do { \ + for (;;) { \ + set_current_state(TASK_INTERRUPTIBLE); \ + if (cond) \ + break; \ + schedule(); \ + } \ + __set_current_state(TASK_RUNNING); \ +} while (0) + +/* + * RCU global state, including node hierarchy. This hierarchy is + * represented in "heap" form in a dense array. The root (first level) + * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second + * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), + * and the third level in ->node[m+1] and following (->node[m+1] referenced + * by ->level[2]). The number of levels is determined by the number of + * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" + * consisting of a single rcu_node. + */ +struct rcu_state { + struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ + struct rcu_node *level[RCU_NUM_LVLS]; /* Hierarchy levels. */ + u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ + u8 levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */ + u8 flavor_mask; /* bit in flavor mask. */ + struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ + void (*call)(struct rcu_head *head, /* call_rcu() flavor. */ + void (*func)(struct rcu_head *head)); + + /* The following fields are guarded by the root rcu_node's lock. */ + + u8 fqs_state ____cacheline_internodealigned_in_smp; + /* Force QS state. */ + u8 boost; /* Subject to priority boost. */ + unsigned long gpnum; /* Current gp number. */ + unsigned long completed; /* # of last completed gp. */ + struct task_struct *gp_kthread; /* Task for grace periods. */ + wait_queue_head_t gp_wq; /* Where GP task waits. */ + short gp_flags; /* Commands for GP task. */ + short gp_state; /* GP kthread sleep state. */ + + /* End of fields guarded by root rcu_node's lock. */ + + raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp; + /* Protect following fields. */ + struct rcu_head *orphan_nxtlist; /* Orphaned callbacks that */ + /* need a grace period. */ + struct rcu_head **orphan_nxttail; /* Tail of above. */ + struct rcu_head *orphan_donelist; /* Orphaned callbacks that */ + /* are ready to invoke. */ + struct rcu_head **orphan_donetail; /* Tail of above. */ + long qlen_lazy; /* Number of lazy callbacks. */ + long qlen; /* Total number of callbacks. */ + /* End of fields guarded by orphan_lock. */ + + struct mutex barrier_mutex; /* Guards barrier fields. */ + atomic_t barrier_cpu_count; /* # CPUs waiting on. */ + struct completion barrier_completion; /* Wake at barrier end. */ + unsigned long n_barrier_done; /* ++ at start and end of */ + /* _rcu_barrier(). */ + /* End of fields guarded by barrier_mutex. */ + + atomic_long_t expedited_start; /* Starting ticket. */ + atomic_long_t expedited_done; /* Done ticket. */ + atomic_long_t expedited_wrap; /* # near-wrap incidents. */ + atomic_long_t expedited_tryfail; /* # acquisition failures. */ + atomic_long_t expedited_workdone1; /* # done by others #1. */ + atomic_long_t expedited_workdone2; /* # done by others #2. */ + atomic_long_t expedited_normal; /* # fallbacks to normal. */ + atomic_long_t expedited_stoppedcpus; /* # successful stop_cpus. */ + atomic_long_t expedited_done_tries; /* # tries to update _done. */ + atomic_long_t expedited_done_lost; /* # times beaten to _done. */ + atomic_long_t expedited_done_exit; /* # times exited _done loop. */ + + unsigned long jiffies_force_qs; /* Time at which to invoke */ + /* force_quiescent_state(). */ + unsigned long n_force_qs; /* Number of calls to */ + /* force_quiescent_state(). */ + unsigned long n_force_qs_lh; /* ~Number of calls leaving */ + /* due to lock unavailable. */ + unsigned long n_force_qs_ngp; /* Number of calls leaving */ + /* due to no GP active. */ + unsigned long gp_start; /* Time at which GP started, */ + /* but in jiffies. */ + unsigned long gp_activity; /* Time of last GP kthread */ + /* activity in jiffies. */ + unsigned long jiffies_stall; /* Time at which to check */ + /* for CPU stalls. */ + unsigned long jiffies_resched; /* Time at which to resched */ + /* a reluctant CPU. */ + unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ + /* GP start. */ + unsigned long gp_max; /* Maximum GP duration in */ + /* jiffies. */ + const char *name; /* Name of structure. */ + char abbr; /* Abbreviated name. */ + struct list_head flavors; /* List of RCU flavors. */ +}; + +/* Values for rcu_state structure's gp_flags field. */ +#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */ +#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */ + +/* Values for rcu_state structure's gp_flags field. */ +#define RCU_GP_WAIT_INIT 0 /* Initial state. */ +#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ +#define RCU_GP_WAIT_FQS 2 /* Wait for force-quiescent-state time. */ + +extern struct list_head rcu_struct_flavors; + +/* Sequence through rcu_state structures for each RCU flavor. */ +#define for_each_rcu_flavor(rsp) \ + list_for_each_entry((rsp), &rcu_struct_flavors, flavors) + +/* + * RCU implementation internal declarations: + */ +extern struct rcu_state rcu_sched_state; +DECLARE_PER_CPU(struct rcu_data, rcu_sched_data); + +extern struct rcu_state rcu_bh_state; +DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); + +#ifdef CONFIG_PREEMPT_RCU +extern struct rcu_state rcu_preempt_state; +DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data); +#endif /* #ifdef CONFIG_PREEMPT_RCU */ + +#ifdef CONFIG_RCU_BOOST +DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status); +DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu); +DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); +DECLARE_PER_CPU(char, rcu_cpu_has_work); +#endif /* #ifdef CONFIG_RCU_BOOST */ + +#ifndef RCU_TREE_NONCORE + +/* Forward declarations for rcutree_plugin.h */ +static void rcu_bootup_announce(void); +static void rcu_preempt_note_context_switch(void); +static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); +#ifdef CONFIG_HOTPLUG_CPU +static bool rcu_preempt_has_tasks(struct rcu_node *rnp); +#endif /* #ifdef CONFIG_HOTPLUG_CPU */ +static void rcu_print_detail_task_stall(struct rcu_state *rsp); +static int rcu_print_task_stall(struct rcu_node *rnp); +static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); +static void rcu_preempt_check_callbacks(void); +void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); +static void __init __rcu_init_preempt(void); +static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); +static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); +static void invoke_rcu_callbacks_kthread(void); +static bool rcu_is_callbacks_kthread(void); +#ifdef CONFIG_RCU_BOOST +static void rcu_preempt_do_callbacks(void); +static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, + struct rcu_node *rnp); +#endif /* #ifdef CONFIG_RCU_BOOST */ +static void __init rcu_spawn_boost_kthreads(void); +static void rcu_prepare_kthreads(int cpu); +static void rcu_cleanup_after_idle(void); +static void rcu_prepare_for_idle(void); +static void rcu_idle_count_callbacks_posted(void); +static bool rcu_preempt_has_tasks(struct rcu_node *rnp); +static void print_cpu_stall_info_begin(void); +static void print_cpu_stall_info(struct rcu_state *rsp, int cpu); +static void print_cpu_stall_info_end(void); +static void zero_cpu_stall_ticks(struct rcu_data *rdp); +static void increment_cpu_stall_ticks(void); +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu); +static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq); +static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp); +static void rcu_init_one_nocb(struct rcu_node *rnp); +static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, + bool lazy, unsigned long flags); +static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, + struct rcu_data *rdp, + unsigned long flags); +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); +static void do_nocb_deferred_wakeup(struct rcu_data *rdp); +static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); +static void rcu_spawn_all_nocb_kthreads(int cpu); +static void __init rcu_spawn_nocb_kthreads(void); +#ifdef CONFIG_RCU_NOCB_CPU +static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp); +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ +static void __maybe_unused rcu_kick_nohz_cpu(int cpu); +static bool init_nocb_callback_list(struct rcu_data *rdp); +static void rcu_sysidle_enter(int irq); +static void rcu_sysidle_exit(int irq); +static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, + unsigned long *maxj); +static bool is_sysidle_rcu_state(struct rcu_state *rsp); +static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, + unsigned long maxj); +static void rcu_bind_gp_kthread(void); +static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp); +static bool rcu_nohz_full_cpu(struct rcu_state *rsp); +static void rcu_dynticks_task_enter(void); +static void rcu_dynticks_task_exit(void); + +#endif /* #ifndef RCU_TREE_NONCORE */ + +#ifdef CONFIG_RCU_TRACE +/* Read out queue lengths for tracing. */ +static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll) +{ +#ifdef CONFIG_RCU_NOCB_CPU + *ql = atomic_long_read(&rdp->nocb_q_count); + *qll = atomic_long_read(&rdp->nocb_q_count_lazy); +#else /* #ifdef CONFIG_RCU_NOCB_CPU */ + *ql = 0; + *qll = 0; +#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ +} +#endif /* #ifdef CONFIG_RCU_TRACE */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h new file mode 100644 index 000000000..8c0ec0f5a --- /dev/null +++ b/kernel/rcu/tree_plugin.h @@ -0,0 +1,3090 @@ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * Internal non-public definitions that provide either classic + * or preemptible semantics. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright Red Hat, 2009 + * Copyright IBM Corporation, 2009 + * + * Author: Ingo Molnar <mingo@elte.hu> + * Paul E. McKenney <paulmck@linux.vnet.ibm.com> + */ + +#include <linux/delay.h> +#include <linux/gfp.h> +#include <linux/oom.h> +#include <linux/smpboot.h> +#include "../time/tick-internal.h" + +#ifdef CONFIG_RCU_BOOST + +#include "../locking/rtmutex_common.h" + +/* + * Control variables for per-CPU and per-rcu_node kthreads. These + * handle all flavors of RCU. + */ +static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); +DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); +DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); +DEFINE_PER_CPU(char, rcu_cpu_has_work); + +#endif /* #ifdef CONFIG_RCU_BOOST */ + +#ifdef CONFIG_RCU_NOCB_CPU +static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ +static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */ +static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ + +/* + * Check the RCU kernel configuration parameters and print informative + * messages about anything out of the ordinary. If you like #ifdef, you + * will love this function. + */ +static void __init rcu_bootup_announce_oddness(void) +{ + if (IS_ENABLED(CONFIG_RCU_TRACE)) + pr_info("\tRCU debugfs-based tracing is enabled.\n"); + if ((IS_ENABLED(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || + (!IS_ENABLED(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32)) + pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n", + CONFIG_RCU_FANOUT); + if (IS_ENABLED(CONFIG_RCU_FANOUT_EXACT)) + pr_info("\tHierarchical RCU autobalancing is disabled.\n"); + if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ)) + pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); + if (IS_ENABLED(CONFIG_PROVE_RCU)) + pr_info("\tRCU lockdep checking is enabled.\n"); + if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_RUNNABLE)) + pr_info("\tRCU torture testing starts during boot.\n"); + if (IS_ENABLED(CONFIG_RCU_CPU_STALL_INFO)) + pr_info("\tAdditional per-CPU info printed with stalls.\n"); + if (NUM_RCU_LVL_4 != 0) + pr_info("\tFour-level hierarchy is enabled.\n"); + if (CONFIG_RCU_FANOUT_LEAF != 16) + pr_info("\tBuild-time adjustment of leaf fanout to %d.\n", + CONFIG_RCU_FANOUT_LEAF); + if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF) + pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); + if (nr_cpu_ids != NR_CPUS) + pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); + if (IS_ENABLED(CONFIG_RCU_BOOST)) + pr_info("\tRCU kthread priority: %d.\n", kthread_prio); +} + +#ifdef CONFIG_PREEMPT_RCU + +RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); +static struct rcu_state *rcu_state_p = &rcu_preempt_state; + +static int rcu_preempted_readers_exp(struct rcu_node *rnp); +static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, + bool wake); + +/* + * Tell them what RCU they are running. + */ +static void __init rcu_bootup_announce(void) +{ + pr_info("Preemptible hierarchical RCU implementation.\n"); + rcu_bootup_announce_oddness(); +} + +/* + * Record a preemptible-RCU quiescent state for the specified CPU. Note + * that this just means that the task currently running on the CPU is + * not in a quiescent state. There might be any number of tasks blocked + * while in an RCU read-side critical section. + * + * As with the other rcu_*_qs() functions, callers to this function + * must disable preemption. + */ +static void rcu_preempt_qs(void) +{ + if (!__this_cpu_read(rcu_preempt_data.passed_quiesce)) { + trace_rcu_grace_period(TPS("rcu_preempt"), + __this_cpu_read(rcu_preempt_data.gpnum), + TPS("cpuqs")); + __this_cpu_write(rcu_preempt_data.passed_quiesce, 1); + barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */ + current->rcu_read_unlock_special.b.need_qs = false; + } +} + +/* + * We have entered the scheduler, and the current task might soon be + * context-switched away from. If this task is in an RCU read-side + * critical section, we will no longer be able to rely on the CPU to + * record that fact, so we enqueue the task on the blkd_tasks list. + * The task will dequeue itself when it exits the outermost enclosing + * RCU read-side critical section. Therefore, the current grace period + * cannot be permitted to complete until the blkd_tasks list entries + * predating the current grace period drain, in other words, until + * rnp->gp_tasks becomes NULL. + * + * Caller must disable preemption. + */ +static void rcu_preempt_note_context_switch(void) +{ + struct task_struct *t = current; + unsigned long flags; + struct rcu_data *rdp; + struct rcu_node *rnp; + + if (t->rcu_read_lock_nesting > 0 && + !t->rcu_read_unlock_special.b.blocked) { + + /* Possibly blocking in an RCU read-side critical section. */ + rdp = this_cpu_ptr(rcu_preempt_state.rda); + rnp = rdp->mynode; + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + t->rcu_read_unlock_special.b.blocked = true; + t->rcu_blocked_node = rnp; + + /* + * If this CPU has already checked in, then this task + * will hold up the next grace period rather than the + * current grace period. Queue the task accordingly. + * If the task is queued for the current grace period + * (i.e., this CPU has not yet passed through a quiescent + * state for the current grace period), then as long + * as that task remains queued, the current grace period + * cannot end. Note that there is some uncertainty as + * to exactly when the current grace period started. + * We take a conservative approach, which can result + * in unnecessarily waiting on tasks that started very + * slightly after the current grace period began. C'est + * la vie!!! + * + * But first, note that the current CPU must still be + * on line! + */ + WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0); + WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); + if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) { + list_add(&t->rcu_node_entry, rnp->gp_tasks->prev); + rnp->gp_tasks = &t->rcu_node_entry; +#ifdef CONFIG_RCU_BOOST + if (rnp->boost_tasks != NULL) + rnp->boost_tasks = rnp->gp_tasks; +#endif /* #ifdef CONFIG_RCU_BOOST */ + } else { + list_add(&t->rcu_node_entry, &rnp->blkd_tasks); + if (rnp->qsmask & rdp->grpmask) + rnp->gp_tasks = &t->rcu_node_entry; + } + trace_rcu_preempt_task(rdp->rsp->name, + t->pid, + (rnp->qsmask & rdp->grpmask) + ? rnp->gpnum + : rnp->gpnum + 1); + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } else if (t->rcu_read_lock_nesting < 0 && + t->rcu_read_unlock_special.s) { + + /* + * Complete exit from RCU read-side critical section on + * behalf of preempted instance of __rcu_read_unlock(). + */ + rcu_read_unlock_special(t); + } + + /* + * Either we were not in an RCU read-side critical section to + * begin with, or we have now recorded that critical section + * globally. Either way, we can now note a quiescent state + * for this CPU. Again, if we were in an RCU read-side critical + * section, and if that critical section was blocking the current + * grace period, then the fact that the task has been enqueued + * means that we continue to block the current grace period. + */ + rcu_preempt_qs(); +} + +/* + * Check for preempted RCU readers blocking the current grace period + * for the specified rcu_node structure. If the caller needs a reliable + * answer, it must hold the rcu_node's ->lock. + */ +static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) +{ + return rnp->gp_tasks != NULL; +} + +/* + * Advance a ->blkd_tasks-list pointer to the next entry, instead + * returning NULL if at the end of the list. + */ +static struct list_head *rcu_next_node_entry(struct task_struct *t, + struct rcu_node *rnp) +{ + struct list_head *np; + + np = t->rcu_node_entry.next; + if (np == &rnp->blkd_tasks) + np = NULL; + return np; +} + +/* + * Return true if the specified rcu_node structure has tasks that were + * preempted within an RCU read-side critical section. + */ +static bool rcu_preempt_has_tasks(struct rcu_node *rnp) +{ + return !list_empty(&rnp->blkd_tasks); +} + +/* + * Handle special cases during rcu_read_unlock(), such as needing to + * notify RCU core processing or task having blocked during the RCU + * read-side critical section. + */ +void rcu_read_unlock_special(struct task_struct *t) +{ + bool empty_exp; + bool empty_norm; + bool empty_exp_now; + unsigned long flags; + struct list_head *np; +#ifdef CONFIG_RCU_BOOST + bool drop_boost_mutex = false; +#endif /* #ifdef CONFIG_RCU_BOOST */ + struct rcu_node *rnp; + union rcu_special special; + + /* NMI handlers cannot block and cannot safely manipulate state. */ + if (in_nmi()) + return; + + local_irq_save(flags); + + /* + * If RCU core is waiting for this CPU to exit critical section, + * let it know that we have done so. Because irqs are disabled, + * t->rcu_read_unlock_special cannot change. + */ + special = t->rcu_read_unlock_special; + if (special.b.need_qs) { + rcu_preempt_qs(); + t->rcu_read_unlock_special.b.need_qs = false; + if (!t->rcu_read_unlock_special.s) { + local_irq_restore(flags); + return; + } + } + + /* Hardware IRQ handlers cannot block, complain if they get here. */ + if (in_irq() || in_serving_softirq()) { + lockdep_rcu_suspicious(__FILE__, __LINE__, + "rcu_read_unlock() from irq or softirq with blocking in critical section!!!\n"); + pr_alert("->rcu_read_unlock_special: %#x (b: %d, nq: %d)\n", + t->rcu_read_unlock_special.s, + t->rcu_read_unlock_special.b.blocked, + t->rcu_read_unlock_special.b.need_qs); + local_irq_restore(flags); + return; + } + + /* Clean up if blocked during RCU read-side critical section. */ + if (special.b.blocked) { + t->rcu_read_unlock_special.b.blocked = false; + + /* + * Remove this task from the list it blocked on. The + * task can migrate while we acquire the lock, but at + * most one time. So at most two passes through loop. + */ + for (;;) { + rnp = t->rcu_blocked_node; + raw_spin_lock(&rnp->lock); /* irqs already disabled. */ + smp_mb__after_unlock_lock(); + if (rnp == t->rcu_blocked_node) + break; + raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + } + empty_norm = !rcu_preempt_blocked_readers_cgp(rnp); + empty_exp = !rcu_preempted_readers_exp(rnp); + smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ + np = rcu_next_node_entry(t, rnp); + list_del_init(&t->rcu_node_entry); + t->rcu_blocked_node = NULL; + trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), + rnp->gpnum, t->pid); + if (&t->rcu_node_entry == rnp->gp_tasks) + rnp->gp_tasks = np; + if (&t->rcu_node_entry == rnp->exp_tasks) + rnp->exp_tasks = np; +#ifdef CONFIG_RCU_BOOST + if (&t->rcu_node_entry == rnp->boost_tasks) + rnp->boost_tasks = np; + /* Snapshot ->boost_mtx ownership with rcu_node lock held. */ + drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; +#endif /* #ifdef CONFIG_RCU_BOOST */ + + /* + * If this was the last task on the current list, and if + * we aren't waiting on any CPUs, report the quiescent state. + * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, + * so we must take a snapshot of the expedited state. + */ + empty_exp_now = !rcu_preempted_readers_exp(rnp); + if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) { + trace_rcu_quiescent_state_report(TPS("preempt_rcu"), + rnp->gpnum, + 0, rnp->qsmask, + rnp->level, + rnp->grplo, + rnp->grphi, + !!rnp->gp_tasks); + rcu_report_unblock_qs_rnp(&rcu_preempt_state, + rnp, flags); + } else { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } + +#ifdef CONFIG_RCU_BOOST + /* Unboost if we were boosted. */ + if (drop_boost_mutex) + rt_mutex_unlock(&rnp->boost_mtx); +#endif /* #ifdef CONFIG_RCU_BOOST */ + + /* + * If this was the last task on the expedited lists, + * then we need to report up the rcu_node hierarchy. + */ + if (!empty_exp && empty_exp_now) + rcu_report_exp_rnp(&rcu_preempt_state, rnp, true); + } else { + local_irq_restore(flags); + } +} + +/* + * Dump detailed information for all tasks blocking the current RCU + * grace period on the specified rcu_node structure. + */ +static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) +{ + unsigned long flags; + struct task_struct *t; + + raw_spin_lock_irqsave(&rnp->lock, flags); + if (!rcu_preempt_blocked_readers_cgp(rnp)) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + t = list_entry(rnp->gp_tasks, + struct task_struct, rcu_node_entry); + list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) + sched_show_task(t); + raw_spin_unlock_irqrestore(&rnp->lock, flags); +} + +/* + * Dump detailed information for all tasks blocking the current RCU + * grace period. + */ +static void rcu_print_detail_task_stall(struct rcu_state *rsp) +{ + struct rcu_node *rnp = rcu_get_root(rsp); + + rcu_print_detail_task_stall_rnp(rnp); + rcu_for_each_leaf_node(rsp, rnp) + rcu_print_detail_task_stall_rnp(rnp); +} + +#ifdef CONFIG_RCU_CPU_STALL_INFO + +static void rcu_print_task_stall_begin(struct rcu_node *rnp) +{ + pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", + rnp->level, rnp->grplo, rnp->grphi); +} + +static void rcu_print_task_stall_end(void) +{ + pr_cont("\n"); +} + +#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ + +static void rcu_print_task_stall_begin(struct rcu_node *rnp) +{ +} + +static void rcu_print_task_stall_end(void) +{ +} + +#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ + +/* + * Scan the current list of tasks blocked within RCU read-side critical + * sections, printing out the tid of each. + */ +static int rcu_print_task_stall(struct rcu_node *rnp) +{ + struct task_struct *t; + int ndetected = 0; + + if (!rcu_preempt_blocked_readers_cgp(rnp)) + return 0; + rcu_print_task_stall_begin(rnp); + t = list_entry(rnp->gp_tasks, + struct task_struct, rcu_node_entry); + list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { + pr_cont(" P%d", t->pid); + ndetected++; + } + rcu_print_task_stall_end(); + return ndetected; +} + +/* + * Check that the list of blocked tasks for the newly completed grace + * period is in fact empty. It is a serious bug to complete a grace + * period that still has RCU readers blocked! This function must be + * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock + * must be held by the caller. + * + * Also, if there are blocked tasks on the list, they automatically + * block the newly created grace period, so set up ->gp_tasks accordingly. + */ +static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) +{ + WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); + if (rcu_preempt_has_tasks(rnp)) + rnp->gp_tasks = rnp->blkd_tasks.next; + WARN_ON_ONCE(rnp->qsmask); +} + +/* + * Check for a quiescent state from the current CPU. When a task blocks, + * the task is recorded in the corresponding CPU's rcu_node structure, + * which is checked elsewhere. + * + * Caller must disable hard irqs. + */ +static void rcu_preempt_check_callbacks(void) +{ + struct task_struct *t = current; + + if (t->rcu_read_lock_nesting == 0) { + rcu_preempt_qs(); + return; + } + if (t->rcu_read_lock_nesting > 0 && + __this_cpu_read(rcu_preempt_data.qs_pending) && + !__this_cpu_read(rcu_preempt_data.passed_quiesce)) + t->rcu_read_unlock_special.b.need_qs = true; +} + +#ifdef CONFIG_RCU_BOOST + +static void rcu_preempt_do_callbacks(void) +{ + rcu_do_batch(&rcu_preempt_state, this_cpu_ptr(&rcu_preempt_data)); +} + +#endif /* #ifdef CONFIG_RCU_BOOST */ + +/* + * Queue a preemptible-RCU callback for invocation after a grace period. + */ +void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_preempt_state, -1, 0); +} +EXPORT_SYMBOL_GPL(call_rcu); + +/** + * synchronize_rcu - wait until a grace period has elapsed. + * + * Control will return to the caller some time after a full grace + * period has elapsed, in other words after all currently executing RCU + * read-side critical sections have completed. Note, however, that + * upon return from synchronize_rcu(), the caller might well be executing + * concurrently with new RCU read-side critical sections that began while + * synchronize_rcu() was waiting. RCU read-side critical sections are + * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. + * + * See the description of synchronize_sched() for more detailed information + * on memory ordering guarantees. + */ +void synchronize_rcu(void) +{ + rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && + !lock_is_held(&rcu_lock_map) && + !lock_is_held(&rcu_sched_lock_map), + "Illegal synchronize_rcu() in RCU read-side critical section"); + if (!rcu_scheduler_active) + return; + if (rcu_gp_is_expedited()) + synchronize_rcu_expedited(); + else + wait_rcu_gp(call_rcu); +} +EXPORT_SYMBOL_GPL(synchronize_rcu); + +static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); +static unsigned long sync_rcu_preempt_exp_count; +static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); + +/* + * Return non-zero if there are any tasks in RCU read-side critical + * sections blocking the current preemptible-RCU expedited grace period. + * If there is no preemptible-RCU expedited grace period currently in + * progress, returns zero unconditionally. + */ +static int rcu_preempted_readers_exp(struct rcu_node *rnp) +{ + return rnp->exp_tasks != NULL; +} + +/* + * return non-zero if there is no RCU expedited grace period in progress + * for the specified rcu_node structure, in other words, if all CPUs and + * tasks covered by the specified rcu_node structure have done their bit + * for the current expedited grace period. Works only for preemptible + * RCU -- other RCU implementation use other means. + * + * Caller must hold sync_rcu_preempt_exp_mutex. + */ +static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) +{ + return !rcu_preempted_readers_exp(rnp) && + ACCESS_ONCE(rnp->expmask) == 0; +} + +/* + * Report the exit from RCU read-side critical section for the last task + * that queued itself during or before the current expedited preemptible-RCU + * grace period. This event is reported either to the rcu_node structure on + * which the task was queued or to one of that rcu_node structure's ancestors, + * recursively up the tree. (Calm down, calm down, we do the recursion + * iteratively!) + * + * Caller must hold sync_rcu_preempt_exp_mutex. + */ +static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, + bool wake) +{ + unsigned long flags; + unsigned long mask; + + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + for (;;) { + if (!sync_rcu_preempt_exp_done(rnp)) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + break; + } + if (rnp->parent == NULL) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + if (wake) { + smp_mb(); /* EGP done before wake_up(). */ + wake_up(&sync_rcu_preempt_exp_wq); + } + break; + } + mask = rnp->grpmask; + raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ + rnp = rnp->parent; + raw_spin_lock(&rnp->lock); /* irqs already disabled */ + smp_mb__after_unlock_lock(); + rnp->expmask &= ~mask; + } +} + +/* + * Snapshot the tasks blocking the newly started preemptible-RCU expedited + * grace period for the specified rcu_node structure, phase 1. If there + * are such tasks, set the ->expmask bits up the rcu_node tree and also + * set the ->expmask bits on the leaf rcu_node structures to tell phase 2 + * that work is needed here. + * + * Caller must hold sync_rcu_preempt_exp_mutex. + */ +static void +sync_rcu_preempt_exp_init1(struct rcu_state *rsp, struct rcu_node *rnp) +{ + unsigned long flags; + unsigned long mask; + struct rcu_node *rnp_up; + + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + WARN_ON_ONCE(rnp->expmask); + WARN_ON_ONCE(rnp->exp_tasks); + if (!rcu_preempt_has_tasks(rnp)) { + /* No blocked tasks, nothing to do. */ + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + /* Call for Phase 2 and propagate ->expmask bits up the tree. */ + rnp->expmask = 1; + rnp_up = rnp; + while (rnp_up->parent) { + mask = rnp_up->grpmask; + rnp_up = rnp_up->parent; + if (rnp_up->expmask & mask) + break; + raw_spin_lock(&rnp_up->lock); /* irqs already off */ + smp_mb__after_unlock_lock(); + rnp_up->expmask |= mask; + raw_spin_unlock(&rnp_up->lock); /* irqs still off */ + } + raw_spin_unlock_irqrestore(&rnp->lock, flags); +} + +/* + * Snapshot the tasks blocking the newly started preemptible-RCU expedited + * grace period for the specified rcu_node structure, phase 2. If the + * leaf rcu_node structure has its ->expmask field set, check for tasks. + * If there are some, clear ->expmask and set ->exp_tasks accordingly, + * then initiate RCU priority boosting. Otherwise, clear ->expmask and + * invoke rcu_report_exp_rnp() to clear out the upper-level ->expmask bits, + * enabling rcu_read_unlock_special() to do the bit-clearing. + * + * Caller must hold sync_rcu_preempt_exp_mutex. + */ +static void +sync_rcu_preempt_exp_init2(struct rcu_state *rsp, struct rcu_node *rnp) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + if (!rnp->expmask) { + /* Phase 1 didn't do anything, so Phase 2 doesn't either. */ + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + + /* Phase 1 is over. */ + rnp->expmask = 0; + + /* + * If there are still blocked tasks, set up ->exp_tasks so that + * rcu_read_unlock_special() will wake us and then boost them. + */ + if (rcu_preempt_has_tasks(rnp)) { + rnp->exp_tasks = rnp->blkd_tasks.next; + rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ + return; + } + + /* No longer any blocked tasks, so undo bit setting. */ + raw_spin_unlock_irqrestore(&rnp->lock, flags); + rcu_report_exp_rnp(rsp, rnp, false); +} + +/** + * synchronize_rcu_expedited - Brute-force RCU grace period + * + * Wait for an RCU-preempt grace period, but expedite it. The basic + * idea is to invoke synchronize_sched_expedited() to push all the tasks to + * the ->blkd_tasks lists and wait for this list to drain. This consumes + * significant time on all CPUs and is unfriendly to real-time workloads, + * so is thus not recommended for any sort of common-case code. + * In fact, if you are using synchronize_rcu_expedited() in a loop, + * please restructure your code to batch your updates, and then Use a + * single synchronize_rcu() instead. + */ +void synchronize_rcu_expedited(void) +{ + struct rcu_node *rnp; + struct rcu_state *rsp = &rcu_preempt_state; + unsigned long snap; + int trycount = 0; + + smp_mb(); /* Caller's modifications seen first by other CPUs. */ + snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1; + smp_mb(); /* Above access cannot bleed into critical section. */ + + /* + * Block CPU-hotplug operations. This means that any CPU-hotplug + * operation that finds an rcu_node structure with tasks in the + * process of being boosted will know that all tasks blocking + * this expedited grace period will already be in the process of + * being boosted. This simplifies the process of moving tasks + * from leaf to root rcu_node structures. + */ + if (!try_get_online_cpus()) { + /* CPU-hotplug operation in flight, fall back to normal GP. */ + wait_rcu_gp(call_rcu); + return; + } + + /* + * Acquire lock, falling back to synchronize_rcu() if too many + * lock-acquisition failures. Of course, if someone does the + * expedited grace period for us, just leave. + */ + while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) { + if (ULONG_CMP_LT(snap, + ACCESS_ONCE(sync_rcu_preempt_exp_count))) { + put_online_cpus(); + goto mb_ret; /* Others did our work for us. */ + } + if (trycount++ < 10) { + udelay(trycount * num_online_cpus()); + } else { + put_online_cpus(); + wait_rcu_gp(call_rcu); + return; + } + } + if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) { + put_online_cpus(); + goto unlock_mb_ret; /* Others did our work for us. */ + } + + /* force all RCU readers onto ->blkd_tasks lists. */ + synchronize_sched_expedited(); + + /* + * Snapshot current state of ->blkd_tasks lists into ->expmask. + * Phase 1 sets bits and phase 2 permits rcu_read_unlock_special() + * to start clearing them. Doing this in one phase leads to + * strange races between setting and clearing bits, so just say "no"! + */ + rcu_for_each_leaf_node(rsp, rnp) + sync_rcu_preempt_exp_init1(rsp, rnp); + rcu_for_each_leaf_node(rsp, rnp) + sync_rcu_preempt_exp_init2(rsp, rnp); + + put_online_cpus(); + + /* Wait for snapshotted ->blkd_tasks lists to drain. */ + rnp = rcu_get_root(rsp); + wait_event(sync_rcu_preempt_exp_wq, + sync_rcu_preempt_exp_done(rnp)); + + /* Clean up and exit. */ + smp_mb(); /* ensure expedited GP seen before counter increment. */ + ACCESS_ONCE(sync_rcu_preempt_exp_count) = + sync_rcu_preempt_exp_count + 1; +unlock_mb_ret: + mutex_unlock(&sync_rcu_preempt_exp_mutex); +mb_ret: + smp_mb(); /* ensure subsequent action seen after grace period. */ +} +EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); + +/** + * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. + * + * Note that this primitive does not necessarily wait for an RCU grace period + * to complete. For example, if there are no RCU callbacks queued anywhere + * in the system, then rcu_barrier() is within its rights to return + * immediately, without waiting for anything, much less an RCU grace period. + */ +void rcu_barrier(void) +{ + _rcu_barrier(&rcu_preempt_state); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + +/* + * Initialize preemptible RCU's state structures. + */ +static void __init __rcu_init_preempt(void) +{ + rcu_init_one(&rcu_preempt_state, &rcu_preempt_data); +} + +/* + * Check for a task exiting while in a preemptible-RCU read-side + * critical section, clean up if so. No need to issue warnings, + * as debug_check_no_locks_held() already does this if lockdep + * is enabled. + */ +void exit_rcu(void) +{ + struct task_struct *t = current; + + if (likely(list_empty(¤t->rcu_node_entry))) + return; + t->rcu_read_lock_nesting = 1; + barrier(); + t->rcu_read_unlock_special.b.blocked = true; + __rcu_read_unlock(); +} + +#else /* #ifdef CONFIG_PREEMPT_RCU */ + +static struct rcu_state *rcu_state_p = &rcu_sched_state; + +/* + * Tell them what RCU they are running. + */ +static void __init rcu_bootup_announce(void) +{ + pr_info("Hierarchical RCU implementation.\n"); + rcu_bootup_announce_oddness(); +} + +/* + * Because preemptible RCU does not exist, we never have to check for + * CPUs being in quiescent states. + */ +static void rcu_preempt_note_context_switch(void) +{ +} + +/* + * Because preemptible RCU does not exist, there are never any preempted + * RCU readers. + */ +static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) +{ + return 0; +} + +/* + * Because there is no preemptible RCU, there can be no readers blocked. + */ +static bool rcu_preempt_has_tasks(struct rcu_node *rnp) +{ + return false; +} + +/* + * Because preemptible RCU does not exist, we never have to check for + * tasks blocked within RCU read-side critical sections. + */ +static void rcu_print_detail_task_stall(struct rcu_state *rsp) +{ +} + +/* + * Because preemptible RCU does not exist, we never have to check for + * tasks blocked within RCU read-side critical sections. + */ +static int rcu_print_task_stall(struct rcu_node *rnp) +{ + return 0; +} + +/* + * Because there is no preemptible RCU, there can be no readers blocked, + * so there is no need to check for blocked tasks. So check only for + * bogus qsmask values. + */ +static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) +{ + WARN_ON_ONCE(rnp->qsmask); +} + +/* + * Because preemptible RCU does not exist, it never has any callbacks + * to check. + */ +static void rcu_preempt_check_callbacks(void) +{ +} + +/* + * Wait for an rcu-preempt grace period, but make it happen quickly. + * But because preemptible RCU does not exist, map to rcu-sched. + */ +void synchronize_rcu_expedited(void) +{ + synchronize_sched_expedited(); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); + +/* + * Because preemptible RCU does not exist, rcu_barrier() is just + * another name for rcu_barrier_sched(). + */ +void rcu_barrier(void) +{ + rcu_barrier_sched(); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + +/* + * Because preemptible RCU does not exist, it need not be initialized. + */ +static void __init __rcu_init_preempt(void) +{ +} + +/* + * Because preemptible RCU does not exist, tasks cannot possibly exit + * while in preemptible RCU read-side critical sections. + */ +void exit_rcu(void) +{ +} + +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ + +#ifdef CONFIG_RCU_BOOST + +#include "../locking/rtmutex_common.h" + +#ifdef CONFIG_RCU_TRACE + +static void rcu_initiate_boost_trace(struct rcu_node *rnp) +{ + if (!rcu_preempt_has_tasks(rnp)) + rnp->n_balk_blkd_tasks++; + else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) + rnp->n_balk_exp_gp_tasks++; + else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) + rnp->n_balk_boost_tasks++; + else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) + rnp->n_balk_notblocked++; + else if (rnp->gp_tasks != NULL && + ULONG_CMP_LT(jiffies, rnp->boost_time)) + rnp->n_balk_notyet++; + else + rnp->n_balk_nos++; +} + +#else /* #ifdef CONFIG_RCU_TRACE */ + +static void rcu_initiate_boost_trace(struct rcu_node *rnp) +{ +} + +#endif /* #else #ifdef CONFIG_RCU_TRACE */ + +static void rcu_wake_cond(struct task_struct *t, int status) +{ + /* + * If the thread is yielding, only wake it when this + * is invoked from idle + */ + if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) + wake_up_process(t); +} + +/* + * Carry out RCU priority boosting on the task indicated by ->exp_tasks + * or ->boost_tasks, advancing the pointer to the next task in the + * ->blkd_tasks list. + * + * Note that irqs must be enabled: boosting the task can block. + * Returns 1 if there are more tasks needing to be boosted. + */ +static int rcu_boost(struct rcu_node *rnp) +{ + unsigned long flags; + struct task_struct *t; + struct list_head *tb; + + if (ACCESS_ONCE(rnp->exp_tasks) == NULL && + ACCESS_ONCE(rnp->boost_tasks) == NULL) + return 0; /* Nothing left to boost. */ + + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + + /* + * Recheck under the lock: all tasks in need of boosting + * might exit their RCU read-side critical sections on their own. + */ + if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return 0; + } + + /* + * Preferentially boost tasks blocking expedited grace periods. + * This cannot starve the normal grace periods because a second + * expedited grace period must boost all blocked tasks, including + * those blocking the pre-existing normal grace period. + */ + if (rnp->exp_tasks != NULL) { + tb = rnp->exp_tasks; + rnp->n_exp_boosts++; + } else { + tb = rnp->boost_tasks; + rnp->n_normal_boosts++; + } + rnp->n_tasks_boosted++; + + /* + * We boost task t by manufacturing an rt_mutex that appears to + * be held by task t. We leave a pointer to that rt_mutex where + * task t can find it, and task t will release the mutex when it + * exits its outermost RCU read-side critical section. Then + * simply acquiring this artificial rt_mutex will boost task + * t's priority. (Thanks to tglx for suggesting this approach!) + * + * Note that task t must acquire rnp->lock to remove itself from + * the ->blkd_tasks list, which it will do from exit() if from + * nowhere else. We therefore are guaranteed that task t will + * stay around at least until we drop rnp->lock. Note that + * rnp->lock also resolves races between our priority boosting + * and task t's exiting its outermost RCU read-side critical + * section. + */ + t = container_of(tb, struct task_struct, rcu_node_entry); + rt_mutex_init_proxy_locked(&rnp->boost_mtx, t); + raw_spin_unlock_irqrestore(&rnp->lock, flags); + /* Lock only for side effect: boosts task t's priority. */ + rt_mutex_lock(&rnp->boost_mtx); + rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ + + return ACCESS_ONCE(rnp->exp_tasks) != NULL || + ACCESS_ONCE(rnp->boost_tasks) != NULL; +} + +/* + * Priority-boosting kthread. One per leaf rcu_node and one for the + * root rcu_node. + */ +static int rcu_boost_kthread(void *arg) +{ + struct rcu_node *rnp = (struct rcu_node *)arg; + int spincnt = 0; + int more2boost; + + trace_rcu_utilization(TPS("Start boost kthread@init")); + for (;;) { + rnp->boost_kthread_status = RCU_KTHREAD_WAITING; + trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); + rcu_wait(rnp->boost_tasks || rnp->exp_tasks); + trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); + rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; + more2boost = rcu_boost(rnp); + if (more2boost) + spincnt++; + else + spincnt = 0; + if (spincnt > 10) { + rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; + trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); + schedule_timeout_interruptible(2); + trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); + spincnt = 0; + } + } + /* NOTREACHED */ + trace_rcu_utilization(TPS("End boost kthread@notreached")); + return 0; +} + +/* + * Check to see if it is time to start boosting RCU readers that are + * blocking the current grace period, and, if so, tell the per-rcu_node + * kthread to start boosting them. If there is an expedited grace + * period in progress, it is always time to boost. + * + * The caller must hold rnp->lock, which this function releases. + * The ->boost_kthread_task is immortal, so we don't need to worry + * about it going away. + */ +static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) + __releases(rnp->lock) +{ + struct task_struct *t; + + if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { + rnp->n_balk_exp_gp_tasks++; + raw_spin_unlock_irqrestore(&rnp->lock, flags); + return; + } + if (rnp->exp_tasks != NULL || + (rnp->gp_tasks != NULL && + rnp->boost_tasks == NULL && + rnp->qsmask == 0 && + ULONG_CMP_GE(jiffies, rnp->boost_time))) { + if (rnp->exp_tasks == NULL) + rnp->boost_tasks = rnp->gp_tasks; + raw_spin_unlock_irqrestore(&rnp->lock, flags); + t = rnp->boost_kthread_task; + if (t) + rcu_wake_cond(t, rnp->boost_kthread_status); + } else { + rcu_initiate_boost_trace(rnp); + raw_spin_unlock_irqrestore(&rnp->lock, flags); + } +} + +/* + * Wake up the per-CPU kthread to invoke RCU callbacks. + */ +static void invoke_rcu_callbacks_kthread(void) +{ + unsigned long flags; + + local_irq_save(flags); + __this_cpu_write(rcu_cpu_has_work, 1); + if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && + current != __this_cpu_read(rcu_cpu_kthread_task)) { + rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), + __this_cpu_read(rcu_cpu_kthread_status)); + } + local_irq_restore(flags); +} + +/* + * Is the current CPU running the RCU-callbacks kthread? + * Caller must have preemption disabled. + */ +static bool rcu_is_callbacks_kthread(void) +{ + return __this_cpu_read(rcu_cpu_kthread_task) == current; +} + +#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) + +/* + * Do priority-boost accounting for the start of a new grace period. + */ +static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) +{ + rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; +} + +/* + * Create an RCU-boost kthread for the specified node if one does not + * already exist. We only create this kthread for preemptible RCU. + * Returns zero if all is well, a negated errno otherwise. + */ +static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, + struct rcu_node *rnp) +{ + int rnp_index = rnp - &rsp->node[0]; + unsigned long flags; + struct sched_param sp; + struct task_struct *t; + + if (&rcu_preempt_state != rsp) + return 0; + + if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0) + return 0; + + rsp->boost = 1; + if (rnp->boost_kthread_task != NULL) + return 0; + t = kthread_create(rcu_boost_kthread, (void *)rnp, + "rcub/%d", rnp_index); + if (IS_ERR(t)) + return PTR_ERR(t); + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + rnp->boost_kthread_task = t; + raw_spin_unlock_irqrestore(&rnp->lock, flags); + sp.sched_priority = kthread_prio; + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); + wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ + return 0; +} + +static void rcu_kthread_do_work(void) +{ + rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data)); + rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data)); + rcu_preempt_do_callbacks(); +} + +static void rcu_cpu_kthread_setup(unsigned int cpu) +{ + struct sched_param sp; + + sp.sched_priority = kthread_prio; + sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); +} + +static void rcu_cpu_kthread_park(unsigned int cpu) +{ + per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; +} + +static int rcu_cpu_kthread_should_run(unsigned int cpu) +{ + return __this_cpu_read(rcu_cpu_has_work); +} + +/* + * Per-CPU kernel thread that invokes RCU callbacks. This replaces the + * RCU softirq used in flavors and configurations of RCU that do not + * support RCU priority boosting. + */ +static void rcu_cpu_kthread(unsigned int cpu) +{ + unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); + char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); + int spincnt; + + for (spincnt = 0; spincnt < 10; spincnt++) { + trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); + local_bh_disable(); + *statusp = RCU_KTHREAD_RUNNING; + this_cpu_inc(rcu_cpu_kthread_loops); + local_irq_disable(); + work = *workp; + *workp = 0; + local_irq_enable(); + if (work) + rcu_kthread_do_work(); + local_bh_enable(); + if (*workp == 0) { + trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); + *statusp = RCU_KTHREAD_WAITING; + return; + } + } + *statusp = RCU_KTHREAD_YIELDING; + trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); + schedule_timeout_interruptible(2); + trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); + *statusp = RCU_KTHREAD_WAITING; +} + +/* + * Set the per-rcu_node kthread's affinity to cover all CPUs that are + * served by the rcu_node in question. The CPU hotplug lock is still + * held, so the value of rnp->qsmaskinit will be stable. + * + * We don't include outgoingcpu in the affinity set, use -1 if there is + * no outgoing CPU. If there are no CPUs left in the affinity set, + * this function allows the kthread to execute on any CPU. + */ +static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) +{ + struct task_struct *t = rnp->boost_kthread_task; + unsigned long mask = rcu_rnp_online_cpus(rnp); + cpumask_var_t cm; + int cpu; + + if (!t) + return; + if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) + return; + for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) + if ((mask & 0x1) && cpu != outgoingcpu) + cpumask_set_cpu(cpu, cm); + if (cpumask_weight(cm) == 0) + cpumask_setall(cm); + set_cpus_allowed_ptr(t, cm); + free_cpumask_var(cm); +} + +static struct smp_hotplug_thread rcu_cpu_thread_spec = { + .store = &rcu_cpu_kthread_task, + .thread_should_run = rcu_cpu_kthread_should_run, + .thread_fn = rcu_cpu_kthread, + .thread_comm = "rcuc/%u", + .setup = rcu_cpu_kthread_setup, + .park = rcu_cpu_kthread_park, +}; + +/* + * Spawn boost kthreads -- called as soon as the scheduler is running. + */ +static void __init rcu_spawn_boost_kthreads(void) +{ + struct rcu_node *rnp; + int cpu; + + for_each_possible_cpu(cpu) + per_cpu(rcu_cpu_has_work, cpu) = 0; + BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); + rcu_for_each_leaf_node(rcu_state_p, rnp) + (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); +} + +static void rcu_prepare_kthreads(int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); + struct rcu_node *rnp = rdp->mynode; + + /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ + if (rcu_scheduler_fully_active) + (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); +} + +#else /* #ifdef CONFIG_RCU_BOOST */ + +static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) + __releases(rnp->lock) +{ + raw_spin_unlock_irqrestore(&rnp->lock, flags); +} + +static void invoke_rcu_callbacks_kthread(void) +{ + WARN_ON_ONCE(1); +} + +static bool rcu_is_callbacks_kthread(void) +{ + return false; +} + +static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) +{ +} + +static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) +{ +} + +static void __init rcu_spawn_boost_kthreads(void) +{ +} + +static void rcu_prepare_kthreads(int cpu) +{ +} + +#endif /* #else #ifdef CONFIG_RCU_BOOST */ + +#if !defined(CONFIG_RCU_FAST_NO_HZ) + +/* + * Check to see if any future RCU-related work will need to be done + * by the current CPU, even if none need be done immediately, returning + * 1 if so. This function is part of the RCU implementation; it is -not- + * an exported member of the RCU API. + * + * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs + * any flavor of RCU. + */ +#ifndef CONFIG_RCU_NOCB_CPU_ALL +int rcu_needs_cpu(unsigned long *delta_jiffies) +{ + *delta_jiffies = ULONG_MAX; + return rcu_cpu_has_callbacks(NULL); +} +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ + +/* + * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up + * after it. + */ +static void rcu_cleanup_after_idle(void) +{ +} + +/* + * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, + * is nothing. + */ +static void rcu_prepare_for_idle(void) +{ +} + +/* + * Don't bother keeping a running count of the number of RCU callbacks + * posted because CONFIG_RCU_FAST_NO_HZ=n. + */ +static void rcu_idle_count_callbacks_posted(void) +{ +} + +#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ + +/* + * This code is invoked when a CPU goes idle, at which point we want + * to have the CPU do everything required for RCU so that it can enter + * the energy-efficient dyntick-idle mode. This is handled by a + * state machine implemented by rcu_prepare_for_idle() below. + * + * The following three proprocessor symbols control this state machine: + * + * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted + * to sleep in dyntick-idle mode with RCU callbacks pending. This + * is sized to be roughly one RCU grace period. Those energy-efficiency + * benchmarkers who might otherwise be tempted to set this to a large + * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your + * system. And if you are -that- concerned about energy efficiency, + * just power the system down and be done with it! + * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is + * permitted to sleep in dyntick-idle mode with only lazy RCU + * callbacks pending. Setting this too high can OOM your system. + * + * The values below work well in practice. If future workloads require + * adjustment, they can be converted into kernel config parameters, though + * making the state machine smarter might be a better option. + */ +#define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ +#define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ + +static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; +module_param(rcu_idle_gp_delay, int, 0644); +static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY; +module_param(rcu_idle_lazy_gp_delay, int, 0644); + +extern int tick_nohz_active; + +/* + * Try to advance callbacks for all flavors of RCU on the current CPU, but + * only if it has been awhile since the last time we did so. Afterwards, + * if there are any callbacks ready for immediate invocation, return true. + */ +static bool __maybe_unused rcu_try_advance_all_cbs(void) +{ + bool cbs_ready = false; + struct rcu_data *rdp; + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + struct rcu_node *rnp; + struct rcu_state *rsp; + + /* Exit early if we advanced recently. */ + if (jiffies == rdtp->last_advance_all) + return false; + rdtp->last_advance_all = jiffies; + + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + rnp = rdp->mynode; + + /* + * Don't bother checking unless a grace period has + * completed since we last checked and there are + * callbacks not yet ready to invoke. + */ + if ((rdp->completed != rnp->completed || + unlikely(ACCESS_ONCE(rdp->gpwrap))) && + rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL]) + note_gp_changes(rsp, rdp); + + if (cpu_has_callbacks_ready_to_invoke(rdp)) + cbs_ready = true; + } + return cbs_ready; +} + +/* + * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready + * to invoke. If the CPU has callbacks, try to advance them. Tell the + * caller to set the timeout based on whether or not there are non-lazy + * callbacks. + * + * The caller must have disabled interrupts. + */ +#ifndef CONFIG_RCU_NOCB_CPU_ALL +int rcu_needs_cpu(unsigned long *dj) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + /* Snapshot to detect later posting of non-lazy callback. */ + rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; + + /* If no callbacks, RCU doesn't need the CPU. */ + if (!rcu_cpu_has_callbacks(&rdtp->all_lazy)) { + *dj = ULONG_MAX; + return 0; + } + + /* Attempt to advance callbacks. */ + if (rcu_try_advance_all_cbs()) { + /* Some ready to invoke, so initiate later invocation. */ + invoke_rcu_core(); + return 1; + } + rdtp->last_accelerate = jiffies; + + /* Request timer delay depending on laziness, and round. */ + if (!rdtp->all_lazy) { + *dj = round_up(rcu_idle_gp_delay + jiffies, + rcu_idle_gp_delay) - jiffies; + } else { + *dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; + } + return 0; +} +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ + +/* + * Prepare a CPU for idle from an RCU perspective. The first major task + * is to sense whether nohz mode has been enabled or disabled via sysfs. + * The second major task is to check to see if a non-lazy callback has + * arrived at a CPU that previously had only lazy callbacks. The third + * major task is to accelerate (that is, assign grace-period numbers to) + * any recently arrived callbacks. + * + * The caller must have disabled interrupts. + */ +static void rcu_prepare_for_idle(void) +{ +#ifndef CONFIG_RCU_NOCB_CPU_ALL + bool needwake; + struct rcu_data *rdp; + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + struct rcu_node *rnp; + struct rcu_state *rsp; + int tne; + + /* Handle nohz enablement switches conservatively. */ + tne = ACCESS_ONCE(tick_nohz_active); + if (tne != rdtp->tick_nohz_enabled_snap) { + if (rcu_cpu_has_callbacks(NULL)) + invoke_rcu_core(); /* force nohz to see update. */ + rdtp->tick_nohz_enabled_snap = tne; + return; + } + if (!tne) + return; + + /* If this is a no-CBs CPU, no callbacks, just return. */ + if (rcu_is_nocb_cpu(smp_processor_id())) + return; + + /* + * If a non-lazy callback arrived at a CPU having only lazy + * callbacks, invoke RCU core for the side-effect of recalculating + * idle duration on re-entry to idle. + */ + if (rdtp->all_lazy && + rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) { + rdtp->all_lazy = false; + rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; + invoke_rcu_core(); + return; + } + + /* + * If we have not yet accelerated this jiffy, accelerate all + * callbacks on this CPU. + */ + if (rdtp->last_accelerate == jiffies) + return; + rdtp->last_accelerate = jiffies; + for_each_rcu_flavor(rsp) { + rdp = this_cpu_ptr(rsp->rda); + if (!*rdp->nxttail[RCU_DONE_TAIL]) + continue; + rnp = rdp->mynode; + raw_spin_lock(&rnp->lock); /* irqs already disabled. */ + smp_mb__after_unlock_lock(); + needwake = rcu_accelerate_cbs(rsp, rnp, rdp); + raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ + if (needwake) + rcu_gp_kthread_wake(rsp); + } +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ +} + +/* + * Clean up for exit from idle. Attempt to advance callbacks based on + * any grace periods that elapsed while the CPU was idle, and if any + * callbacks are now ready to invoke, initiate invocation. + */ +static void rcu_cleanup_after_idle(void) +{ +#ifndef CONFIG_RCU_NOCB_CPU_ALL + if (rcu_is_nocb_cpu(smp_processor_id())) + return; + if (rcu_try_advance_all_cbs()) + invoke_rcu_core(); +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ +} + +/* + * Keep a running count of the number of non-lazy callbacks posted + * on this CPU. This running counter (which is never decremented) allows + * rcu_prepare_for_idle() to detect when something out of the idle loop + * posts a callback, even if an equal number of callbacks are invoked. + * Of course, callbacks should only be posted from within a trace event + * designed to be called from idle or from within RCU_NONIDLE(). + */ +static void rcu_idle_count_callbacks_posted(void) +{ + __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); +} + +/* + * Data for flushing lazy RCU callbacks at OOM time. + */ +static atomic_t oom_callback_count; +static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); + +/* + * RCU OOM callback -- decrement the outstanding count and deliver the + * wake-up if we are the last one. + */ +static void rcu_oom_callback(struct rcu_head *rhp) +{ + if (atomic_dec_and_test(&oom_callback_count)) + wake_up(&oom_callback_wq); +} + +/* + * Post an rcu_oom_notify callback on the current CPU if it has at + * least one lazy callback. This will unnecessarily post callbacks + * to CPUs that already have a non-lazy callback at the end of their + * callback list, but this is an infrequent operation, so accept some + * extra overhead to keep things simple. + */ +static void rcu_oom_notify_cpu(void *unused) +{ + struct rcu_state *rsp; + struct rcu_data *rdp; + + for_each_rcu_flavor(rsp) { + rdp = raw_cpu_ptr(rsp->rda); + if (rdp->qlen_lazy != 0) { + atomic_inc(&oom_callback_count); + rsp->call(&rdp->oom_head, rcu_oom_callback); + } + } +} + +/* + * If low on memory, ensure that each CPU has a non-lazy callback. + * This will wake up CPUs that have only lazy callbacks, in turn + * ensuring that they free up the corresponding memory in a timely manner. + * Because an uncertain amount of memory will be freed in some uncertain + * timeframe, we do not claim to have freed anything. + */ +static int rcu_oom_notify(struct notifier_block *self, + unsigned long notused, void *nfreed) +{ + int cpu; + + /* Wait for callbacks from earlier instance to complete. */ + wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); + smp_mb(); /* Ensure callback reuse happens after callback invocation. */ + + /* + * Prevent premature wakeup: ensure that all increments happen + * before there is a chance of the counter reaching zero. + */ + atomic_set(&oom_callback_count, 1); + + get_online_cpus(); + for_each_online_cpu(cpu) { + smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); + cond_resched_rcu_qs(); + } + put_online_cpus(); + + /* Unconditionally decrement: no need to wake ourselves up. */ + atomic_dec(&oom_callback_count); + + return NOTIFY_OK; +} + +static struct notifier_block rcu_oom_nb = { + .notifier_call = rcu_oom_notify +}; + +static int __init rcu_register_oom_notifier(void) +{ + register_oom_notifier(&rcu_oom_nb); + return 0; +} +early_initcall(rcu_register_oom_notifier); + +#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ + +#ifdef CONFIG_RCU_CPU_STALL_INFO + +#ifdef CONFIG_RCU_FAST_NO_HZ + +static void print_cpu_stall_fast_no_hz(char *cp, int cpu) +{ + struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); + unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap; + + sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", + rdtp->last_accelerate & 0xffff, jiffies & 0xffff, + ulong2long(nlpd), + rdtp->all_lazy ? 'L' : '.', + rdtp->tick_nohz_enabled_snap ? '.' : 'D'); +} + +#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ + +static void print_cpu_stall_fast_no_hz(char *cp, int cpu) +{ + *cp = '\0'; +} + +#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ + +/* Initiate the stall-info list. */ +static void print_cpu_stall_info_begin(void) +{ + pr_cont("\n"); +} + +/* + * Print out diagnostic information for the specified stalled CPU. + * + * If the specified CPU is aware of the current RCU grace period + * (flavor specified by rsp), then print the number of scheduling + * clock interrupts the CPU has taken during the time that it has + * been aware. Otherwise, print the number of RCU grace periods + * that this CPU is ignorant of, for example, "1" if the CPU was + * aware of the previous grace period. + * + * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. + */ +static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) +{ + char fast_no_hz[72]; + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_dynticks *rdtp = rdp->dynticks; + char *ticks_title; + unsigned long ticks_value; + + if (rsp->gpnum == rdp->gpnum) { + ticks_title = "ticks this GP"; + ticks_value = rdp->ticks_this_gp; + } else { + ticks_title = "GPs behind"; + ticks_value = rsp->gpnum - rdp->gpnum; + } + print_cpu_stall_fast_no_hz(fast_no_hz, cpu); + pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u fqs=%ld %s\n", + cpu, ticks_value, ticks_title, + atomic_read(&rdtp->dynticks) & 0xfff, + rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, + rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), + ACCESS_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart, + fast_no_hz); +} + +/* Terminate the stall-info list. */ +static void print_cpu_stall_info_end(void) +{ + pr_err("\t"); +} + +/* Zero ->ticks_this_gp for all flavors of RCU. */ +static void zero_cpu_stall_ticks(struct rcu_data *rdp) +{ + rdp->ticks_this_gp = 0; + rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); +} + +/* Increment ->ticks_this_gp for all flavors of RCU. */ +static void increment_cpu_stall_ticks(void) +{ + struct rcu_state *rsp; + + for_each_rcu_flavor(rsp) + raw_cpu_inc(rsp->rda->ticks_this_gp); +} + +#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ + +static void print_cpu_stall_info_begin(void) +{ + pr_cont(" {"); +} + +static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) +{ + pr_cont(" %d", cpu); +} + +static void print_cpu_stall_info_end(void) +{ + pr_cont("} "); +} + +static void zero_cpu_stall_ticks(struct rcu_data *rdp) +{ +} + +static void increment_cpu_stall_ticks(void) +{ +} + +#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ + +#ifdef CONFIG_RCU_NOCB_CPU + +/* + * Offload callback processing from the boot-time-specified set of CPUs + * specified by rcu_nocb_mask. For each CPU in the set, there is a + * kthread created that pulls the callbacks from the corresponding CPU, + * waits for a grace period to elapse, and invokes the callbacks. + * The no-CBs CPUs do a wake_up() on their kthread when they insert + * a callback into any empty list, unless the rcu_nocb_poll boot parameter + * has been specified, in which case each kthread actively polls its + * CPU. (Which isn't so great for energy efficiency, but which does + * reduce RCU's overhead on that CPU.) + * + * This is intended to be used in conjunction with Frederic Weisbecker's + * adaptive-idle work, which would seriously reduce OS jitter on CPUs + * running CPU-bound user-mode computations. + * + * Offloading of callback processing could also in theory be used as + * an energy-efficiency measure because CPUs with no RCU callbacks + * queued are more aggressive about entering dyntick-idle mode. + */ + + +/* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ +static int __init rcu_nocb_setup(char *str) +{ + alloc_bootmem_cpumask_var(&rcu_nocb_mask); + have_rcu_nocb_mask = true; + cpulist_parse(str, rcu_nocb_mask); + return 1; +} +__setup("rcu_nocbs=", rcu_nocb_setup); + +static int __init parse_rcu_nocb_poll(char *arg) +{ + rcu_nocb_poll = 1; + return 0; +} +early_param("rcu_nocb_poll", parse_rcu_nocb_poll); + +/* + * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended + * grace period. + */ +static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) +{ + wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]); +} + +/* + * Set the root rcu_node structure's ->need_future_gp field + * based on the sum of those of all rcu_node structures. This does + * double-count the root rcu_node structure's requests, but this + * is necessary to handle the possibility of a rcu_nocb_kthread() + * having awakened during the time that the rcu_node structures + * were being updated for the end of the previous grace period. + */ +static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) +{ + rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq; +} + +static void rcu_init_one_nocb(struct rcu_node *rnp) +{ + init_waitqueue_head(&rnp->nocb_gp_wq[0]); + init_waitqueue_head(&rnp->nocb_gp_wq[1]); +} + +#ifndef CONFIG_RCU_NOCB_CPU_ALL +/* Is the specified CPU a no-CBs CPU? */ +bool rcu_is_nocb_cpu(int cpu) +{ + if (have_rcu_nocb_mask) + return cpumask_test_cpu(cpu, rcu_nocb_mask); + return false; +} +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ + +/* + * Kick the leader kthread for this NOCB group. + */ +static void wake_nocb_leader(struct rcu_data *rdp, bool force) +{ + struct rcu_data *rdp_leader = rdp->nocb_leader; + + if (!ACCESS_ONCE(rdp_leader->nocb_kthread)) + return; + if (ACCESS_ONCE(rdp_leader->nocb_leader_sleep) || force) { + /* Prior smp_mb__after_atomic() orders against prior enqueue. */ + ACCESS_ONCE(rdp_leader->nocb_leader_sleep) = false; + wake_up(&rdp_leader->nocb_wq); + } +} + +/* + * Does the specified CPU need an RCU callback for the specified flavor + * of rcu_barrier()? + */ +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + unsigned long ret; +#ifdef CONFIG_PROVE_RCU + struct rcu_head *rhp; +#endif /* #ifdef CONFIG_PROVE_RCU */ + + /* + * Check count of all no-CBs callbacks awaiting invocation. + * There needs to be a barrier before this function is called, + * but associated with a prior determination that no more + * callbacks would be posted. In the worst case, the first + * barrier in _rcu_barrier() suffices (but the caller cannot + * necessarily rely on this, not a substitute for the caller + * getting the concurrency design right!). There must also be + * a barrier between the following load an posting of a callback + * (if a callback is in fact needed). This is associated with an + * atomic_inc() in the caller. + */ + ret = atomic_long_read(&rdp->nocb_q_count); + +#ifdef CONFIG_PROVE_RCU + rhp = ACCESS_ONCE(rdp->nocb_head); + if (!rhp) + rhp = ACCESS_ONCE(rdp->nocb_gp_head); + if (!rhp) + rhp = ACCESS_ONCE(rdp->nocb_follower_head); + + /* Having no rcuo kthread but CBs after scheduler starts is bad! */ + if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp && + rcu_scheduler_fully_active) { + /* RCU callback enqueued before CPU first came online??? */ + pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n", + cpu, rhp->func); + WARN_ON_ONCE(1); + } +#endif /* #ifdef CONFIG_PROVE_RCU */ + + return !!ret; +} + +/* + * Enqueue the specified string of rcu_head structures onto the specified + * CPU's no-CBs lists. The CPU is specified by rdp, the head of the + * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy + * counts are supplied by rhcount and rhcount_lazy. + * + * If warranted, also wake up the kthread servicing this CPUs queues. + */ +static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, + struct rcu_head *rhp, + struct rcu_head **rhtp, + int rhcount, int rhcount_lazy, + unsigned long flags) +{ + int len; + struct rcu_head **old_rhpp; + struct task_struct *t; + + /* Enqueue the callback on the nocb list and update counts. */ + atomic_long_add(rhcount, &rdp->nocb_q_count); + /* rcu_barrier() relies on ->nocb_q_count add before xchg. */ + old_rhpp = xchg(&rdp->nocb_tail, rhtp); + ACCESS_ONCE(*old_rhpp) = rhp; + atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); + smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */ + + /* If we are not being polled and there is a kthread, awaken it ... */ + t = ACCESS_ONCE(rdp->nocb_kthread); + if (rcu_nocb_poll || !t) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeNotPoll")); + return; + } + len = atomic_long_read(&rdp->nocb_q_count); + if (old_rhpp == &rdp->nocb_head) { + if (!irqs_disabled_flags(flags)) { + /* ... if queue was empty ... */ + wake_nocb_leader(rdp, false); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeEmpty")); + } else { + rdp->nocb_defer_wakeup = RCU_NOGP_WAKE; + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeEmptyIsDeferred")); + } + rdp->qlen_last_fqs_check = 0; + } else if (len > rdp->qlen_last_fqs_check + qhimark) { + /* ... or if many callbacks queued. */ + if (!irqs_disabled_flags(flags)) { + wake_nocb_leader(rdp, true); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeOvf")); + } else { + rdp->nocb_defer_wakeup = RCU_NOGP_WAKE_FORCE; + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeOvfIsDeferred")); + } + rdp->qlen_last_fqs_check = LONG_MAX / 2; + } else { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); + } + return; +} + +/* + * This is a helper for __call_rcu(), which invokes this when the normal + * callback queue is inoperable. If this is not a no-CBs CPU, this + * function returns failure back to __call_rcu(), which can complain + * appropriately. + * + * Otherwise, this function queues the callback where the corresponding + * "rcuo" kthread can find it. + */ +static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, + bool lazy, unsigned long flags) +{ + + if (!rcu_is_nocb_cpu(rdp->cpu)) + return false; + __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy, flags); + if (__is_kfree_rcu_offset((unsigned long)rhp->func)) + trace_rcu_kfree_callback(rdp->rsp->name, rhp, + (unsigned long)rhp->func, + -atomic_long_read(&rdp->nocb_q_count_lazy), + -atomic_long_read(&rdp->nocb_q_count)); + else + trace_rcu_callback(rdp->rsp->name, rhp, + -atomic_long_read(&rdp->nocb_q_count_lazy), + -atomic_long_read(&rdp->nocb_q_count)); + + /* + * If called from an extended quiescent state with interrupts + * disabled, invoke the RCU core in order to allow the idle-entry + * deferred-wakeup check to function. + */ + if (irqs_disabled_flags(flags) && + !rcu_is_watching() && + cpu_online(smp_processor_id())) + invoke_rcu_core(); + + return true; +} + +/* + * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is + * not a no-CBs CPU. + */ +static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, + struct rcu_data *rdp, + unsigned long flags) +{ + long ql = rsp->qlen; + long qll = rsp->qlen_lazy; + + /* If this is not a no-CBs CPU, tell the caller to do it the old way. */ + if (!rcu_is_nocb_cpu(smp_processor_id())) + return false; + rsp->qlen = 0; + rsp->qlen_lazy = 0; + + /* First, enqueue the donelist, if any. This preserves CB ordering. */ + if (rsp->orphan_donelist != NULL) { + __call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist, + rsp->orphan_donetail, ql, qll, flags); + ql = qll = 0; + rsp->orphan_donelist = NULL; + rsp->orphan_donetail = &rsp->orphan_donelist; + } + if (rsp->orphan_nxtlist != NULL) { + __call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist, + rsp->orphan_nxttail, ql, qll, flags); + ql = qll = 0; + rsp->orphan_nxtlist = NULL; + rsp->orphan_nxttail = &rsp->orphan_nxtlist; + } + return true; +} + +/* + * If necessary, kick off a new grace period, and either way wait + * for a subsequent grace period to complete. + */ +static void rcu_nocb_wait_gp(struct rcu_data *rdp) +{ + unsigned long c; + bool d; + unsigned long flags; + bool needwake; + struct rcu_node *rnp = rdp->mynode; + + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + needwake = rcu_start_future_gp(rnp, rdp, &c); + raw_spin_unlock_irqrestore(&rnp->lock, flags); + if (needwake) + rcu_gp_kthread_wake(rdp->rsp); + + /* + * Wait for the grace period. Do so interruptibly to avoid messing + * up the load average. + */ + trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait")); + for (;;) { + wait_event_interruptible( + rnp->nocb_gp_wq[c & 0x1], + (d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c))); + if (likely(d)) + break; + WARN_ON(signal_pending(current)); + trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait")); + } + trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait")); + smp_mb(); /* Ensure that CB invocation happens after GP end. */ +} + +/* + * Leaders come here to wait for additional callbacks to show up. + * This function does not return until callbacks appear. + */ +static void nocb_leader_wait(struct rcu_data *my_rdp) +{ + bool firsttime = true; + bool gotcbs; + struct rcu_data *rdp; + struct rcu_head **tail; + +wait_again: + + /* Wait for callbacks to appear. */ + if (!rcu_nocb_poll) { + trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep"); + wait_event_interruptible(my_rdp->nocb_wq, + !ACCESS_ONCE(my_rdp->nocb_leader_sleep)); + /* Memory barrier handled by smp_mb() calls below and repoll. */ + } else if (firsttime) { + firsttime = false; /* Don't drown trace log with "Poll"! */ + trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Poll"); + } + + /* + * Each pass through the following loop checks a follower for CBs. + * We are our own first follower. Any CBs found are moved to + * nocb_gp_head, where they await a grace period. + */ + gotcbs = false; + for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { + rdp->nocb_gp_head = ACCESS_ONCE(rdp->nocb_head); + if (!rdp->nocb_gp_head) + continue; /* No CBs here, try next follower. */ + + /* Move callbacks to wait-for-GP list, which is empty. */ + ACCESS_ONCE(rdp->nocb_head) = NULL; + rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); + gotcbs = true; + } + + /* + * If there were no callbacks, sleep a bit, rescan after a + * memory barrier, and go retry. + */ + if (unlikely(!gotcbs)) { + if (!rcu_nocb_poll) + trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, + "WokeEmpty"); + WARN_ON(signal_pending(current)); + schedule_timeout_interruptible(1); + + /* Rescan in case we were a victim of memory ordering. */ + my_rdp->nocb_leader_sleep = true; + smp_mb(); /* Ensure _sleep true before scan. */ + for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) + if (ACCESS_ONCE(rdp->nocb_head)) { + /* Found CB, so short-circuit next wait. */ + my_rdp->nocb_leader_sleep = false; + break; + } + goto wait_again; + } + + /* Wait for one grace period. */ + rcu_nocb_wait_gp(my_rdp); + + /* + * We left ->nocb_leader_sleep unset to reduce cache thrashing. + * We set it now, but recheck for new callbacks while + * traversing our follower list. + */ + my_rdp->nocb_leader_sleep = true; + smp_mb(); /* Ensure _sleep true before scan of ->nocb_head. */ + + /* Each pass through the following loop wakes a follower, if needed. */ + for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { + if (ACCESS_ONCE(rdp->nocb_head)) + my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/ + if (!rdp->nocb_gp_head) + continue; /* No CBs, so no need to wake follower. */ + + /* Append callbacks to follower's "done" list. */ + tail = xchg(&rdp->nocb_follower_tail, rdp->nocb_gp_tail); + *tail = rdp->nocb_gp_head; + smp_mb__after_atomic(); /* Store *tail before wakeup. */ + if (rdp != my_rdp && tail == &rdp->nocb_follower_head) { + /* + * List was empty, wake up the follower. + * Memory barriers supplied by atomic_long_add(). + */ + wake_up(&rdp->nocb_wq); + } + } + + /* If we (the leader) don't have CBs, go wait some more. */ + if (!my_rdp->nocb_follower_head) + goto wait_again; +} + +/* + * Followers come here to wait for additional callbacks to show up. + * This function does not return until callbacks appear. + */ +static void nocb_follower_wait(struct rcu_data *rdp) +{ + bool firsttime = true; + + for (;;) { + if (!rcu_nocb_poll) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + "FollowerSleep"); + wait_event_interruptible(rdp->nocb_wq, + ACCESS_ONCE(rdp->nocb_follower_head)); + } else if (firsttime) { + /* Don't drown trace log with "Poll"! */ + firsttime = false; + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "Poll"); + } + if (smp_load_acquire(&rdp->nocb_follower_head)) { + /* ^^^ Ensure CB invocation follows _head test. */ + return; + } + if (!rcu_nocb_poll) + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + "WokeEmpty"); + WARN_ON(signal_pending(current)); + schedule_timeout_interruptible(1); + } +} + +/* + * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes + * callbacks queued by the corresponding no-CBs CPU, however, there is + * an optional leader-follower relationship so that the grace-period + * kthreads don't have to do quite so many wakeups. + */ +static int rcu_nocb_kthread(void *arg) +{ + int c, cl; + struct rcu_head *list; + struct rcu_head *next; + struct rcu_head **tail; + struct rcu_data *rdp = arg; + + /* Each pass through this loop invokes one batch of callbacks */ + for (;;) { + /* Wait for callbacks. */ + if (rdp->nocb_leader == rdp) + nocb_leader_wait(rdp); + else + nocb_follower_wait(rdp); + + /* Pull the ready-to-invoke callbacks onto local list. */ + list = ACCESS_ONCE(rdp->nocb_follower_head); + BUG_ON(!list); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty"); + ACCESS_ONCE(rdp->nocb_follower_head) = NULL; + tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head); + + /* Each pass through the following loop invokes a callback. */ + trace_rcu_batch_start(rdp->rsp->name, + atomic_long_read(&rdp->nocb_q_count_lazy), + atomic_long_read(&rdp->nocb_q_count), -1); + c = cl = 0; + while (list) { + next = list->next; + /* Wait for enqueuing to complete, if needed. */ + while (next == NULL && &list->next != tail) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WaitQueue")); + schedule_timeout_interruptible(1); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WokeQueue")); + next = list->next; + } + debug_rcu_head_unqueue(list); + local_bh_disable(); + if (__rcu_reclaim(rdp->rsp->name, list)) + cl++; + c++; + local_bh_enable(); + list = next; + } + trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); + smp_mb__before_atomic(); /* _add after CB invocation. */ + atomic_long_add(-c, &rdp->nocb_q_count); + atomic_long_add(-cl, &rdp->nocb_q_count_lazy); + rdp->n_nocbs_invoked += c; + } + return 0; +} + +/* Is a deferred wakeup of rcu_nocb_kthread() required? */ +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) +{ + return ACCESS_ONCE(rdp->nocb_defer_wakeup); +} + +/* Do a deferred wakeup of rcu_nocb_kthread(). */ +static void do_nocb_deferred_wakeup(struct rcu_data *rdp) +{ + int ndw; + + if (!rcu_nocb_need_deferred_wakeup(rdp)) + return; + ndw = ACCESS_ONCE(rdp->nocb_defer_wakeup); + ACCESS_ONCE(rdp->nocb_defer_wakeup) = RCU_NOGP_WAKE_NOT; + wake_nocb_leader(rdp, ndw == RCU_NOGP_WAKE_FORCE); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWake")); +} + +void __init rcu_init_nohz(void) +{ + int cpu; + bool need_rcu_nocb_mask = true; + struct rcu_state *rsp; + +#ifdef CONFIG_RCU_NOCB_CPU_NONE + need_rcu_nocb_mask = false; +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ + +#if defined(CONFIG_NO_HZ_FULL) + if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) + need_rcu_nocb_mask = true; +#endif /* #if defined(CONFIG_NO_HZ_FULL) */ + + if (!have_rcu_nocb_mask && need_rcu_nocb_mask) { + if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { + pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); + return; + } + have_rcu_nocb_mask = true; + } + if (!have_rcu_nocb_mask) + return; + +#ifdef CONFIG_RCU_NOCB_CPU_ZERO + pr_info("\tOffload RCU callbacks from CPU 0\n"); + cpumask_set_cpu(0, rcu_nocb_mask); +#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */ +#ifdef CONFIG_RCU_NOCB_CPU_ALL + pr_info("\tOffload RCU callbacks from all CPUs\n"); + cpumask_copy(rcu_nocb_mask, cpu_possible_mask); +#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ +#if defined(CONFIG_NO_HZ_FULL) + if (tick_nohz_full_running) + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); +#endif /* #if defined(CONFIG_NO_HZ_FULL) */ + + if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { + pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); + cpumask_and(rcu_nocb_mask, cpu_possible_mask, + rcu_nocb_mask); + } + pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n", + cpumask_pr_args(rcu_nocb_mask)); + if (rcu_nocb_poll) + pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); + + for_each_rcu_flavor(rsp) { + for_each_cpu(cpu, rcu_nocb_mask) + init_nocb_callback_list(per_cpu_ptr(rsp->rda, cpu)); + rcu_organize_nocb_kthreads(rsp); + } +} + +/* Initialize per-rcu_data variables for no-CBs CPUs. */ +static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) +{ + rdp->nocb_tail = &rdp->nocb_head; + init_waitqueue_head(&rdp->nocb_wq); + rdp->nocb_follower_tail = &rdp->nocb_follower_head; +} + +/* + * If the specified CPU is a no-CBs CPU that does not already have its + * rcuo kthread for the specified RCU flavor, spawn it. If the CPUs are + * brought online out of order, this can require re-organizing the + * leader-follower relationships. + */ +static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) +{ + struct rcu_data *rdp; + struct rcu_data *rdp_last; + struct rcu_data *rdp_old_leader; + struct rcu_data *rdp_spawn = per_cpu_ptr(rsp->rda, cpu); + struct task_struct *t; + + /* + * If this isn't a no-CBs CPU or if it already has an rcuo kthread, + * then nothing to do. + */ + if (!rcu_is_nocb_cpu(cpu) || rdp_spawn->nocb_kthread) + return; + + /* If we didn't spawn the leader first, reorganize! */ + rdp_old_leader = rdp_spawn->nocb_leader; + if (rdp_old_leader != rdp_spawn && !rdp_old_leader->nocb_kthread) { + rdp_last = NULL; + rdp = rdp_old_leader; + do { + rdp->nocb_leader = rdp_spawn; + if (rdp_last && rdp != rdp_spawn) + rdp_last->nocb_next_follower = rdp; + if (rdp == rdp_spawn) { + rdp = rdp->nocb_next_follower; + } else { + rdp_last = rdp; + rdp = rdp->nocb_next_follower; + rdp_last->nocb_next_follower = NULL; + } + } while (rdp); + rdp_spawn->nocb_next_follower = rdp_old_leader; + } + + /* Spawn the kthread for this CPU and RCU flavor. */ + t = kthread_run(rcu_nocb_kthread, rdp_spawn, + "rcuo%c/%d", rsp->abbr, cpu); + BUG_ON(IS_ERR(t)); + ACCESS_ONCE(rdp_spawn->nocb_kthread) = t; +} + +/* + * If the specified CPU is a no-CBs CPU that does not already have its + * rcuo kthreads, spawn them. + */ +static void rcu_spawn_all_nocb_kthreads(int cpu) +{ + struct rcu_state *rsp; + + if (rcu_scheduler_fully_active) + for_each_rcu_flavor(rsp) + rcu_spawn_one_nocb_kthread(rsp, cpu); +} + +/* + * Once the scheduler is running, spawn rcuo kthreads for all online + * no-CBs CPUs. This assumes that the early_initcall()s happen before + * non-boot CPUs come online -- if this changes, we will need to add + * some mutual exclusion. + */ +static void __init rcu_spawn_nocb_kthreads(void) +{ + int cpu; + + for_each_online_cpu(cpu) + rcu_spawn_all_nocb_kthreads(cpu); +} + +/* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ +static int rcu_nocb_leader_stride = -1; +module_param(rcu_nocb_leader_stride, int, 0444); + +/* + * Initialize leader-follower relationships for all no-CBs CPU. + */ +static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) +{ + int cpu; + int ls = rcu_nocb_leader_stride; + int nl = 0; /* Next leader. */ + struct rcu_data *rdp; + struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ + struct rcu_data *rdp_prev = NULL; + + if (!have_rcu_nocb_mask) + return; + if (ls == -1) { + ls = int_sqrt(nr_cpu_ids); + rcu_nocb_leader_stride = ls; + } + + /* + * Each pass through this loop sets up one rcu_data structure and + * spawns one rcu_nocb_kthread(). + */ + for_each_cpu(cpu, rcu_nocb_mask) { + rdp = per_cpu_ptr(rsp->rda, cpu); + if (rdp->cpu >= nl) { + /* New leader, set up for followers & next leader. */ + nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls; + rdp->nocb_leader = rdp; + rdp_leader = rdp; + } else { + /* Another follower, link to previous leader. */ + rdp->nocb_leader = rdp_leader; + rdp_prev->nocb_next_follower = rdp; + } + rdp_prev = rdp; + } +} + +/* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ +static bool init_nocb_callback_list(struct rcu_data *rdp) +{ + if (!rcu_is_nocb_cpu(rdp->cpu)) + return false; + + /* If there are early-boot callbacks, move them to nocb lists. */ + if (rdp->nxtlist) { + rdp->nocb_head = rdp->nxtlist; + rdp->nocb_tail = rdp->nxttail[RCU_NEXT_TAIL]; + atomic_long_set(&rdp->nocb_q_count, rdp->qlen); + atomic_long_set(&rdp->nocb_q_count_lazy, rdp->qlen_lazy); + rdp->nxtlist = NULL; + rdp->qlen = 0; + rdp->qlen_lazy = 0; + } + rdp->nxttail[RCU_NEXT_TAIL] = NULL; + return true; +} + +#else /* #ifdef CONFIG_RCU_NOCB_CPU */ + +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) +{ + WARN_ON_ONCE(1); /* Should be dead code. */ + return false; +} + +static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) +{ +} + +static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) +{ +} + +static void rcu_init_one_nocb(struct rcu_node *rnp) +{ +} + +static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, + bool lazy, unsigned long flags) +{ + return false; +} + +static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, + struct rcu_data *rdp, + unsigned long flags) +{ + return false; +} + +static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) +{ +} + +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) +{ + return false; +} + +static void do_nocb_deferred_wakeup(struct rcu_data *rdp) +{ +} + +static void rcu_spawn_all_nocb_kthreads(int cpu) +{ +} + +static void __init rcu_spawn_nocb_kthreads(void) +{ +} + +static bool init_nocb_callback_list(struct rcu_data *rdp) +{ + return false; +} + +#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ + +/* + * An adaptive-ticks CPU can potentially execute in kernel mode for an + * arbitrarily long period of time with the scheduling-clock tick turned + * off. RCU will be paying attention to this CPU because it is in the + * kernel, but the CPU cannot be guaranteed to be executing the RCU state + * machine because the scheduling-clock tick has been disabled. Therefore, + * if an adaptive-ticks CPU is failing to respond to the current grace + * period and has not be idle from an RCU perspective, kick it. + */ +static void __maybe_unused rcu_kick_nohz_cpu(int cpu) +{ +#ifdef CONFIG_NO_HZ_FULL + if (tick_nohz_full_cpu(cpu)) + smp_send_reschedule(cpu); +#endif /* #ifdef CONFIG_NO_HZ_FULL */ +} + + +#ifdef CONFIG_NO_HZ_FULL_SYSIDLE + +static int full_sysidle_state; /* Current system-idle state. */ +#define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ +#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ +#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ +#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ +#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ + +/* + * Invoked to note exit from irq or task transition to idle. Note that + * usermode execution does -not- count as idle here! After all, we want + * to detect full-system idle states, not RCU quiescent states and grace + * periods. The caller must have disabled interrupts. + */ +static void rcu_sysidle_enter(int irq) +{ + unsigned long j; + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + /* If there are no nohz_full= CPUs, no need to track this. */ + if (!tick_nohz_full_enabled()) + return; + + /* Adjust nesting, check for fully idle. */ + if (irq) { + rdtp->dynticks_idle_nesting--; + WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); + if (rdtp->dynticks_idle_nesting != 0) + return; /* Still not fully idle. */ + } else { + if ((rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) == + DYNTICK_TASK_NEST_VALUE) { + rdtp->dynticks_idle_nesting = 0; + } else { + rdtp->dynticks_idle_nesting -= DYNTICK_TASK_NEST_VALUE; + WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); + return; /* Still not fully idle. */ + } + } + + /* Record start of fully idle period. */ + j = jiffies; + ACCESS_ONCE(rdtp->dynticks_idle_jiffies) = j; + smp_mb__before_atomic(); + atomic_inc(&rdtp->dynticks_idle); + smp_mb__after_atomic(); + WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1); +} + +/* + * Unconditionally force exit from full system-idle state. This is + * invoked when a normal CPU exits idle, but must be called separately + * for the timekeeping CPU (tick_do_timer_cpu). The reason for this + * is that the timekeeping CPU is permitted to take scheduling-clock + * interrupts while the system is in system-idle state, and of course + * rcu_sysidle_exit() has no way of distinguishing a scheduling-clock + * interrupt from any other type of interrupt. + */ +void rcu_sysidle_force_exit(void) +{ + int oldstate = ACCESS_ONCE(full_sysidle_state); + int newoldstate; + + /* + * Each pass through the following loop attempts to exit full + * system-idle state. If contention proves to be a problem, + * a trylock-based contention tree could be used here. + */ + while (oldstate > RCU_SYSIDLE_SHORT) { + newoldstate = cmpxchg(&full_sysidle_state, + oldstate, RCU_SYSIDLE_NOT); + if (oldstate == newoldstate && + oldstate == RCU_SYSIDLE_FULL_NOTED) { + rcu_kick_nohz_cpu(tick_do_timer_cpu); + return; /* We cleared it, done! */ + } + oldstate = newoldstate; + } + smp_mb(); /* Order initial oldstate fetch vs. later non-idle work. */ +} + +/* + * Invoked to note entry to irq or task transition from idle. Note that + * usermode execution does -not- count as idle here! The caller must + * have disabled interrupts. + */ +static void rcu_sysidle_exit(int irq) +{ + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + /* If there are no nohz_full= CPUs, no need to track this. */ + if (!tick_nohz_full_enabled()) + return; + + /* Adjust nesting, check for already non-idle. */ + if (irq) { + rdtp->dynticks_idle_nesting++; + WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); + if (rdtp->dynticks_idle_nesting != 1) + return; /* Already non-idle. */ + } else { + /* + * Allow for irq misnesting. Yes, it really is possible + * to enter an irq handler then never leave it, and maybe + * also vice versa. Handle both possibilities. + */ + if (rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) { + rdtp->dynticks_idle_nesting += DYNTICK_TASK_NEST_VALUE; + WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); + return; /* Already non-idle. */ + } else { + rdtp->dynticks_idle_nesting = DYNTICK_TASK_EXIT_IDLE; + } + } + + /* Record end of idle period. */ + smp_mb__before_atomic(); + atomic_inc(&rdtp->dynticks_idle); + smp_mb__after_atomic(); + WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1)); + + /* + * If we are the timekeeping CPU, we are permitted to be non-idle + * during a system-idle state. This must be the case, because + * the timekeeping CPU has to take scheduling-clock interrupts + * during the time that the system is transitioning to full + * system-idle state. This means that the timekeeping CPU must + * invoke rcu_sysidle_force_exit() directly if it does anything + * more than take a scheduling-clock interrupt. + */ + if (smp_processor_id() == tick_do_timer_cpu) + return; + + /* Update system-idle state: We are clearly no longer fully idle! */ + rcu_sysidle_force_exit(); +} + +/* + * Check to see if the current CPU is idle. Note that usermode execution + * does not count as idle. The caller must have disabled interrupts, + * and must be running on tick_do_timer_cpu. + */ +static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, + unsigned long *maxj) +{ + int cur; + unsigned long j; + struct rcu_dynticks *rdtp = rdp->dynticks; + + /* If there are no nohz_full= CPUs, don't check system-wide idleness. */ + if (!tick_nohz_full_enabled()) + return; + + /* + * If some other CPU has already reported non-idle, if this is + * not the flavor of RCU that tracks sysidle state, or if this + * is an offline or the timekeeping CPU, nothing to do. + */ + if (!*isidle || rdp->rsp != rcu_state_p || + cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) + return; + /* Verify affinity of current kthread. */ + WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); + + /* Pick up current idle and NMI-nesting counter and check. */ + cur = atomic_read(&rdtp->dynticks_idle); + if (cur & 0x1) { + *isidle = false; /* We are not idle! */ + return; + } + smp_mb(); /* Read counters before timestamps. */ + + /* Pick up timestamps. */ + j = ACCESS_ONCE(rdtp->dynticks_idle_jiffies); + /* If this CPU entered idle more recently, update maxj timestamp. */ + if (ULONG_CMP_LT(*maxj, j)) + *maxj = j; +} + +/* + * Is this the flavor of RCU that is handling full-system idle? + */ +static bool is_sysidle_rcu_state(struct rcu_state *rsp) +{ + return rsp == rcu_state_p; +} + +/* + * Return a delay in jiffies based on the number of CPUs, rcu_node + * leaf fanout, and jiffies tick rate. The idea is to allow larger + * systems more time to transition to full-idle state in order to + * avoid the cache thrashing that otherwise occur on the state variable. + * Really small systems (less than a couple of tens of CPUs) should + * instead use a single global atomically incremented counter, and later + * versions of this will automatically reconfigure themselves accordingly. + */ +static unsigned long rcu_sysidle_delay(void) +{ + if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) + return 0; + return DIV_ROUND_UP(nr_cpu_ids * HZ, rcu_fanout_leaf * 1000); +} + +/* + * Advance the full-system-idle state. This is invoked when all of + * the non-timekeeping CPUs are idle. + */ +static void rcu_sysidle(unsigned long j) +{ + /* Check the current state. */ + switch (ACCESS_ONCE(full_sysidle_state)) { + case RCU_SYSIDLE_NOT: + + /* First time all are idle, so note a short idle period. */ + ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_SHORT; + break; + + case RCU_SYSIDLE_SHORT: + + /* + * Idle for a bit, time to advance to next state? + * cmpxchg failure means race with non-idle, let them win. + */ + if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) + (void)cmpxchg(&full_sysidle_state, + RCU_SYSIDLE_SHORT, RCU_SYSIDLE_LONG); + break; + + case RCU_SYSIDLE_LONG: + + /* + * Do an additional check pass before advancing to full. + * cmpxchg failure means race with non-idle, let them win. + */ + if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) + (void)cmpxchg(&full_sysidle_state, + RCU_SYSIDLE_LONG, RCU_SYSIDLE_FULL); + break; + + default: + break; + } +} + +/* + * Found a non-idle non-timekeeping CPU, so kick the system-idle state + * back to the beginning. + */ +static void rcu_sysidle_cancel(void) +{ + smp_mb(); + if (full_sysidle_state > RCU_SYSIDLE_SHORT) + ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT; +} + +/* + * Update the sysidle state based on the results of a force-quiescent-state + * scan of the CPUs' dyntick-idle state. + */ +static void rcu_sysidle_report(struct rcu_state *rsp, int isidle, + unsigned long maxj, bool gpkt) +{ + if (rsp != rcu_state_p) + return; /* Wrong flavor, ignore. */ + if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) + return; /* Running state machine from timekeeping CPU. */ + if (isidle) + rcu_sysidle(maxj); /* More idle! */ + else + rcu_sysidle_cancel(); /* Idle is over. */ +} + +/* + * Wrapper for rcu_sysidle_report() when called from the grace-period + * kthread's context. + */ +static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, + unsigned long maxj) +{ + /* If there are no nohz_full= CPUs, no need to track this. */ + if (!tick_nohz_full_enabled()) + return; + + rcu_sysidle_report(rsp, isidle, maxj, true); +} + +/* Callback and function for forcing an RCU grace period. */ +struct rcu_sysidle_head { + struct rcu_head rh; + int inuse; +}; + +static void rcu_sysidle_cb(struct rcu_head *rhp) +{ + struct rcu_sysidle_head *rshp; + + /* + * The following memory barrier is needed to replace the + * memory barriers that would normally be in the memory + * allocator. + */ + smp_mb(); /* grace period precedes setting inuse. */ + + rshp = container_of(rhp, struct rcu_sysidle_head, rh); + ACCESS_ONCE(rshp->inuse) = 0; +} + +/* + * Check to see if the system is fully idle, other than the timekeeping CPU. + * The caller must have disabled interrupts. This is not intended to be + * called unless tick_nohz_full_enabled(). + */ +bool rcu_sys_is_idle(void) +{ + static struct rcu_sysidle_head rsh; + int rss = ACCESS_ONCE(full_sysidle_state); + + if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu)) + return false; + + /* Handle small-system case by doing a full scan of CPUs. */ + if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) { + int oldrss = rss - 1; + + /* + * One pass to advance to each state up to _FULL. + * Give up if any pass fails to advance the state. + */ + while (rss < RCU_SYSIDLE_FULL && oldrss < rss) { + int cpu; + bool isidle = true; + unsigned long maxj = jiffies - ULONG_MAX / 4; + struct rcu_data *rdp; + + /* Scan all the CPUs looking for nonidle CPUs. */ + for_each_possible_cpu(cpu) { + rdp = per_cpu_ptr(rcu_state_p->rda, cpu); + rcu_sysidle_check_cpu(rdp, &isidle, &maxj); + if (!isidle) + break; + } + rcu_sysidle_report(rcu_state_p, isidle, maxj, false); + oldrss = rss; + rss = ACCESS_ONCE(full_sysidle_state); + } + } + + /* If this is the first observation of an idle period, record it. */ + if (rss == RCU_SYSIDLE_FULL) { + rss = cmpxchg(&full_sysidle_state, + RCU_SYSIDLE_FULL, RCU_SYSIDLE_FULL_NOTED); + return rss == RCU_SYSIDLE_FULL; + } + + smp_mb(); /* ensure rss load happens before later caller actions. */ + + /* If already fully idle, tell the caller (in case of races). */ + if (rss == RCU_SYSIDLE_FULL_NOTED) + return true; + + /* + * If we aren't there yet, and a grace period is not in flight, + * initiate a grace period. Either way, tell the caller that + * we are not there yet. We use an xchg() rather than an assignment + * to make up for the memory barriers that would otherwise be + * provided by the memory allocator. + */ + if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL && + !rcu_gp_in_progress(rcu_state_p) && + !rsh.inuse && xchg(&rsh.inuse, 1) == 0) + call_rcu(&rsh.rh, rcu_sysidle_cb); + return false; +} + +/* + * Initialize dynticks sysidle state for CPUs coming online. + */ +static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) +{ + rdtp->dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE; +} + +#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ + +static void rcu_sysidle_enter(int irq) +{ +} + +static void rcu_sysidle_exit(int irq) +{ +} + +static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, + unsigned long *maxj) +{ +} + +static bool is_sysidle_rcu_state(struct rcu_state *rsp) +{ + return false; +} + +static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, + unsigned long maxj) +{ +} + +static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) +{ +} + +#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ + +/* + * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the + * grace-period kthread will do force_quiescent_state() processing? + * The idea is to avoid waking up RCU core processing on such a + * CPU unless the grace period has extended for too long. + * + * This code relies on the fact that all NO_HZ_FULL CPUs are also + * CONFIG_RCU_NOCB_CPU CPUs. + */ +static bool rcu_nohz_full_cpu(struct rcu_state *rsp) +{ +#ifdef CONFIG_NO_HZ_FULL + if (tick_nohz_full_cpu(smp_processor_id()) && + (!rcu_gp_in_progress(rsp) || + ULONG_CMP_LT(jiffies, ACCESS_ONCE(rsp->gp_start) + HZ))) + return 1; +#endif /* #ifdef CONFIG_NO_HZ_FULL */ + return 0; +} + +/* + * Bind the grace-period kthread for the sysidle flavor of RCU to the + * timekeeping CPU. + */ +static void rcu_bind_gp_kthread(void) +{ + int __maybe_unused cpu; + + if (!tick_nohz_full_enabled()) + return; +#ifdef CONFIG_NO_HZ_FULL_SYSIDLE + cpu = tick_do_timer_cpu; + if (cpu >= 0 && cpu < nr_cpu_ids) + set_cpus_allowed_ptr(current, cpumask_of(cpu)); +#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ + housekeeping_affine(current); +#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ +} + +/* Record the current task on dyntick-idle entry. */ +static void rcu_dynticks_task_enter(void) +{ +#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) + ACCESS_ONCE(current->rcu_tasks_idle_cpu) = smp_processor_id(); +#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ +} + +/* Record no current task on dyntick-idle exit. */ +static void rcu_dynticks_task_exit(void) +{ +#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) + ACCESS_ONCE(current->rcu_tasks_idle_cpu) = -1; +#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ +} diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c new file mode 100644 index 000000000..f92361efd --- /dev/null +++ b/kernel/rcu/tree_trace.c @@ -0,0 +1,505 @@ +/* + * Read-Copy Update tracing for classic implementation + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2008 + * + * Papers: http://www.rdrop.com/users/paulmck/RCU + * + * For detailed explanation of Read-Copy Update mechanism see - + * Documentation/RCU + * + */ +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/rcupdate.h> +#include <linux/interrupt.h> +#include <linux/sched.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/module.h> +#include <linux/completion.h> +#include <linux/moduleparam.h> +#include <linux/percpu.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/mutex.h> +#include <linux/debugfs.h> +#include <linux/seq_file.h> + +#define RCU_TREE_NONCORE +#include "tree.h" + +DECLARE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr); + +static int r_open(struct inode *inode, struct file *file, + const struct seq_operations *op) +{ + int ret = seq_open(file, op); + if (!ret) { + struct seq_file *m = (struct seq_file *)file->private_data; + m->private = inode->i_private; + } + return ret; +} + +static void *r_start(struct seq_file *m, loff_t *pos) +{ + struct rcu_state *rsp = (struct rcu_state *)m->private; + *pos = cpumask_next(*pos - 1, cpu_possible_mask); + if ((*pos) < nr_cpu_ids) + return per_cpu_ptr(rsp->rda, *pos); + return NULL; +} + +static void *r_next(struct seq_file *m, void *v, loff_t *pos) +{ + (*pos)++; + return r_start(m, pos); +} + +static void r_stop(struct seq_file *m, void *v) +{ +} + +static int show_rcubarrier(struct seq_file *m, void *v) +{ + struct rcu_state *rsp = (struct rcu_state *)m->private; + seq_printf(m, "bcc: %d nbd: %lu\n", + atomic_read(&rsp->barrier_cpu_count), + rsp->n_barrier_done); + return 0; +} + +static int rcubarrier_open(struct inode *inode, struct file *file) +{ + return single_open(file, show_rcubarrier, inode->i_private); +} + +static const struct file_operations rcubarrier_fops = { + .owner = THIS_MODULE, + .open = rcubarrier_open, + .read = seq_read, + .llseek = no_llseek, + .release = single_release, +}; + +#ifdef CONFIG_RCU_BOOST + +static char convert_kthread_status(unsigned int kthread_status) +{ + if (kthread_status > RCU_KTHREAD_MAX) + return '?'; + return "SRWOY"[kthread_status]; +} + +#endif /* #ifdef CONFIG_RCU_BOOST */ + +static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) +{ + long ql, qll; + + if (!rdp->beenonline) + return; + seq_printf(m, "%3d%cc=%ld g=%ld pq=%d/%d qp=%d", + rdp->cpu, + cpu_is_offline(rdp->cpu) ? '!' : ' ', + ulong2long(rdp->completed), ulong2long(rdp->gpnum), + rdp->passed_quiesce, + rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu), + rdp->qs_pending); + seq_printf(m, " dt=%d/%llx/%d df=%lu", + atomic_read(&rdp->dynticks->dynticks), + rdp->dynticks->dynticks_nesting, + rdp->dynticks->dynticks_nmi_nesting, + rdp->dynticks_fqs); + seq_printf(m, " of=%lu", rdp->offline_fqs); + rcu_nocb_q_lengths(rdp, &ql, &qll); + qll += rdp->qlen_lazy; + ql += rdp->qlen; + seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c", + qll, ql, + ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] != + rdp->nxttail[RCU_NEXT_TAIL]], + ".R"[rdp->nxttail[RCU_WAIT_TAIL] != + rdp->nxttail[RCU_NEXT_READY_TAIL]], + ".W"[rdp->nxttail[RCU_DONE_TAIL] != + rdp->nxttail[RCU_WAIT_TAIL]], + ".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]]); +#ifdef CONFIG_RCU_BOOST + seq_printf(m, " kt=%d/%c ktl=%x", + per_cpu(rcu_cpu_has_work, rdp->cpu), + convert_kthread_status(per_cpu(rcu_cpu_kthread_status, + rdp->cpu)), + per_cpu(rcu_cpu_kthread_loops, rdp->cpu) & 0xffff); +#endif /* #ifdef CONFIG_RCU_BOOST */ + seq_printf(m, " b=%ld", rdp->blimit); + seq_printf(m, " ci=%lu nci=%lu co=%lu ca=%lu\n", + rdp->n_cbs_invoked, rdp->n_nocbs_invoked, + rdp->n_cbs_orphaned, rdp->n_cbs_adopted); +} + +static int show_rcudata(struct seq_file *m, void *v) +{ + print_one_rcu_data(m, (struct rcu_data *)v); + return 0; +} + +static const struct seq_operations rcudate_op = { + .start = r_start, + .next = r_next, + .stop = r_stop, + .show = show_rcudata, +}; + +static int rcudata_open(struct inode *inode, struct file *file) +{ + return r_open(inode, file, &rcudate_op); +} + +static const struct file_operations rcudata_fops = { + .owner = THIS_MODULE, + .open = rcudata_open, + .read = seq_read, + .llseek = no_llseek, + .release = seq_release, +}; + +static int show_rcuexp(struct seq_file *m, void *v) +{ + struct rcu_state *rsp = (struct rcu_state *)m->private; + + seq_printf(m, "s=%lu d=%lu w=%lu tf=%lu wd1=%lu wd2=%lu n=%lu sc=%lu dt=%lu dl=%lu dx=%lu\n", + atomic_long_read(&rsp->expedited_start), + atomic_long_read(&rsp->expedited_done), + atomic_long_read(&rsp->expedited_wrap), + atomic_long_read(&rsp->expedited_tryfail), + atomic_long_read(&rsp->expedited_workdone1), + atomic_long_read(&rsp->expedited_workdone2), + atomic_long_read(&rsp->expedited_normal), + atomic_long_read(&rsp->expedited_stoppedcpus), + atomic_long_read(&rsp->expedited_done_tries), + atomic_long_read(&rsp->expedited_done_lost), + atomic_long_read(&rsp->expedited_done_exit)); + return 0; +} + +static int rcuexp_open(struct inode *inode, struct file *file) +{ + return single_open(file, show_rcuexp, inode->i_private); +} + +static const struct file_operations rcuexp_fops = { + .owner = THIS_MODULE, + .open = rcuexp_open, + .read = seq_read, + .llseek = no_llseek, + .release = single_release, +}; + +#ifdef CONFIG_RCU_BOOST + +static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp) +{ + seq_printf(m, "%d:%d tasks=%c%c%c%c kt=%c ntb=%lu neb=%lu nnb=%lu ", + rnp->grplo, rnp->grphi, + "T."[list_empty(&rnp->blkd_tasks)], + "N."[!rnp->gp_tasks], + "E."[!rnp->exp_tasks], + "B."[!rnp->boost_tasks], + convert_kthread_status(rnp->boost_kthread_status), + rnp->n_tasks_boosted, rnp->n_exp_boosts, + rnp->n_normal_boosts); + seq_printf(m, "j=%04x bt=%04x\n", + (int)(jiffies & 0xffff), + (int)(rnp->boost_time & 0xffff)); + seq_printf(m, " balk: nt=%lu egt=%lu bt=%lu nb=%lu ny=%lu nos=%lu\n", + rnp->n_balk_blkd_tasks, + rnp->n_balk_exp_gp_tasks, + rnp->n_balk_boost_tasks, + rnp->n_balk_notblocked, + rnp->n_balk_notyet, + rnp->n_balk_nos); +} + +static int show_rcu_node_boost(struct seq_file *m, void *unused) +{ + struct rcu_node *rnp; + + rcu_for_each_leaf_node(&rcu_preempt_state, rnp) + print_one_rcu_node_boost(m, rnp); + return 0; +} + +static int rcu_node_boost_open(struct inode *inode, struct file *file) +{ + return single_open(file, show_rcu_node_boost, NULL); +} + +static const struct file_operations rcu_node_boost_fops = { + .owner = THIS_MODULE, + .open = rcu_node_boost_open, + .read = seq_read, + .llseek = no_llseek, + .release = single_release, +}; + +#endif /* #ifdef CONFIG_RCU_BOOST */ + +static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp) +{ + unsigned long gpnum; + int level = 0; + struct rcu_node *rnp; + + gpnum = rsp->gpnum; + seq_printf(m, "c=%ld g=%ld s=%d jfq=%ld j=%x ", + ulong2long(rsp->completed), ulong2long(gpnum), + rsp->fqs_state, + (long)(rsp->jiffies_force_qs - jiffies), + (int)(jiffies & 0xffff)); + seq_printf(m, "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld/%ld\n", + rsp->n_force_qs, rsp->n_force_qs_ngp, + rsp->n_force_qs - rsp->n_force_qs_ngp, + ACCESS_ONCE(rsp->n_force_qs_lh), rsp->qlen_lazy, rsp->qlen); + for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < rcu_num_nodes; rnp++) { + if (rnp->level != level) { + seq_puts(m, "\n"); + level = rnp->level; + } + seq_printf(m, "%lx/%lx->%lx %c%c>%c %d:%d ^%d ", + rnp->qsmask, rnp->qsmaskinit, rnp->qsmaskinitnext, + ".G"[rnp->gp_tasks != NULL], + ".E"[rnp->exp_tasks != NULL], + ".T"[!list_empty(&rnp->blkd_tasks)], + rnp->grplo, rnp->grphi, rnp->grpnum); + } + seq_puts(m, "\n"); +} + +static int show_rcuhier(struct seq_file *m, void *v) +{ + struct rcu_state *rsp = (struct rcu_state *)m->private; + print_one_rcu_state(m, rsp); + return 0; +} + +static int rcuhier_open(struct inode *inode, struct file *file) +{ + return single_open(file, show_rcuhier, inode->i_private); +} + +static const struct file_operations rcuhier_fops = { + .owner = THIS_MODULE, + .open = rcuhier_open, + .read = seq_read, + .llseek = no_llseek, + .release = single_release, +}; + +static void show_one_rcugp(struct seq_file *m, struct rcu_state *rsp) +{ + unsigned long flags; + unsigned long completed; + unsigned long gpnum; + unsigned long gpage; + unsigned long gpmax; + struct rcu_node *rnp = &rsp->node[0]; + + raw_spin_lock_irqsave(&rnp->lock, flags); + completed = ACCESS_ONCE(rsp->completed); + gpnum = ACCESS_ONCE(rsp->gpnum); + if (completed == gpnum) + gpage = 0; + else + gpage = jiffies - rsp->gp_start; + gpmax = rsp->gp_max; + raw_spin_unlock_irqrestore(&rnp->lock, flags); + seq_printf(m, "completed=%ld gpnum=%ld age=%ld max=%ld\n", + ulong2long(completed), ulong2long(gpnum), gpage, gpmax); +} + +static int show_rcugp(struct seq_file *m, void *v) +{ + struct rcu_state *rsp = (struct rcu_state *)m->private; + show_one_rcugp(m, rsp); + return 0; +} + +static int rcugp_open(struct inode *inode, struct file *file) +{ + return single_open(file, show_rcugp, inode->i_private); +} + +static const struct file_operations rcugp_fops = { + .owner = THIS_MODULE, + .open = rcugp_open, + .read = seq_read, + .llseek = no_llseek, + .release = single_release, +}; + +static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp) +{ + if (!rdp->beenonline) + return; + seq_printf(m, "%3d%cnp=%ld ", + rdp->cpu, + cpu_is_offline(rdp->cpu) ? '!' : ' ', + rdp->n_rcu_pending); + seq_printf(m, "qsp=%ld rpq=%ld cbr=%ld cng=%ld ", + rdp->n_rp_qs_pending, + rdp->n_rp_report_qs, + rdp->n_rp_cb_ready, + rdp->n_rp_cpu_needs_gp); + seq_printf(m, "gpc=%ld gps=%ld nn=%ld ndw%ld\n", + rdp->n_rp_gp_completed, + rdp->n_rp_gp_started, + rdp->n_rp_nocb_defer_wakeup, + rdp->n_rp_need_nothing); +} + +static int show_rcu_pending(struct seq_file *m, void *v) +{ + print_one_rcu_pending(m, (struct rcu_data *)v); + return 0; +} + +static const struct seq_operations rcu_pending_op = { + .start = r_start, + .next = r_next, + .stop = r_stop, + .show = show_rcu_pending, +}; + +static int rcu_pending_open(struct inode *inode, struct file *file) +{ + return r_open(inode, file, &rcu_pending_op); +} + +static const struct file_operations rcu_pending_fops = { + .owner = THIS_MODULE, + .open = rcu_pending_open, + .read = seq_read, + .llseek = no_llseek, + .release = seq_release, +}; + +static int show_rcutorture(struct seq_file *m, void *unused) +{ + seq_printf(m, "rcutorture test sequence: %lu %s\n", + rcutorture_testseq >> 1, + (rcutorture_testseq & 0x1) ? "(test in progress)" : ""); + seq_printf(m, "rcutorture update version number: %lu\n", + rcutorture_vernum); + return 0; +} + +static int rcutorture_open(struct inode *inode, struct file *file) +{ + return single_open(file, show_rcutorture, NULL); +} + +static const struct file_operations rcutorture_fops = { + .owner = THIS_MODULE, + .open = rcutorture_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +static struct dentry *rcudir; + +static int __init rcutree_trace_init(void) +{ + struct rcu_state *rsp; + struct dentry *retval; + struct dentry *rspdir; + + rcudir = debugfs_create_dir("rcu", NULL); + if (!rcudir) + goto free_out; + + for_each_rcu_flavor(rsp) { + rspdir = debugfs_create_dir(rsp->name, rcudir); + if (!rspdir) + goto free_out; + + retval = debugfs_create_file("rcudata", 0444, + rspdir, rsp, &rcudata_fops); + if (!retval) + goto free_out; + + retval = debugfs_create_file("rcuexp", 0444, + rspdir, rsp, &rcuexp_fops); + if (!retval) + goto free_out; + + retval = debugfs_create_file("rcu_pending", 0444, + rspdir, rsp, &rcu_pending_fops); + if (!retval) + goto free_out; + + retval = debugfs_create_file("rcubarrier", 0444, + rspdir, rsp, &rcubarrier_fops); + if (!retval) + goto free_out; + +#ifdef CONFIG_RCU_BOOST + if (rsp == &rcu_preempt_state) { + retval = debugfs_create_file("rcuboost", 0444, + rspdir, NULL, &rcu_node_boost_fops); + if (!retval) + goto free_out; + } +#endif + + retval = debugfs_create_file("rcugp", 0444, + rspdir, rsp, &rcugp_fops); + if (!retval) + goto free_out; + + retval = debugfs_create_file("rcuhier", 0444, + rspdir, rsp, &rcuhier_fops); + if (!retval) + goto free_out; + } + + retval = debugfs_create_file("rcutorture", 0444, rcudir, + NULL, &rcutorture_fops); + if (!retval) + goto free_out; + return 0; +free_out: + debugfs_remove_recursive(rcudir); + return 1; +} + +static void __exit rcutree_trace_cleanup(void) +{ + debugfs_remove_recursive(rcudir); +} + + +module_init(rcutree_trace_init); +module_exit(rcutree_trace_cleanup); + +MODULE_AUTHOR("Paul E. McKenney"); +MODULE_DESCRIPTION("Read-Copy Update tracing for hierarchical implementation"); +MODULE_LICENSE("GPL"); diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c new file mode 100644 index 000000000..1f133350d --- /dev/null +++ b/kernel/rcu/update.c @@ -0,0 +1,831 @@ +/* + * Read-Copy Update mechanism for mutual exclusion + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, you can access it online at + * http://www.gnu.org/licenses/gpl-2.0.html. + * + * Copyright IBM Corporation, 2001 + * + * Authors: Dipankar Sarma <dipankar@in.ibm.com> + * Manfred Spraul <manfred@colorfullife.com> + * + * Based on the original work by Paul McKenney <paulmck@us.ibm.com> + * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. + * Papers: + * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf + * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) + * + * For detailed explanation of Read-Copy Update mechanism see - + * http://lse.sourceforge.net/locking/rcupdate.html + * + */ +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/spinlock.h> +#include <linux/smp.h> +#include <linux/interrupt.h> +#include <linux/sched.h> +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/percpu.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/mutex.h> +#include <linux/export.h> +#include <linux/hardirq.h> +#include <linux/delay.h> +#include <linux/module.h> +#include <linux/kthread.h> +#include <linux/tick.h> + +#define CREATE_TRACE_POINTS + +#include "rcu.h" + +MODULE_ALIAS("rcupdate"); +#ifdef MODULE_PARAM_PREFIX +#undef MODULE_PARAM_PREFIX +#endif +#define MODULE_PARAM_PREFIX "rcupdate." + +module_param(rcu_expedited, int, 0); + +#ifndef CONFIG_TINY_RCU + +static atomic_t rcu_expedited_nesting = + ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0); + +/* + * Should normal grace-period primitives be expedited? Intended for + * use within RCU. Note that this function takes the rcu_expedited + * sysfs/boot variable into account as well as the rcu_expedite_gp() + * nesting. So looping on rcu_unexpedite_gp() until rcu_gp_is_expedited() + * returns false is a -really- bad idea. + */ +bool rcu_gp_is_expedited(void) +{ + return rcu_expedited || atomic_read(&rcu_expedited_nesting); +} +EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); + +/** + * rcu_expedite_gp - Expedite future RCU grace periods + * + * After a call to this function, future calls to synchronize_rcu() and + * friends act as the corresponding synchronize_rcu_expedited() function + * had instead been called. + */ +void rcu_expedite_gp(void) +{ + atomic_inc(&rcu_expedited_nesting); +} +EXPORT_SYMBOL_GPL(rcu_expedite_gp); + +/** + * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation + * + * Undo a prior call to rcu_expedite_gp(). If all prior calls to + * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(), + * and if the rcu_expedited sysfs/boot parameter is not set, then all + * subsequent calls to synchronize_rcu() and friends will return to + * their normal non-expedited behavior. + */ +void rcu_unexpedite_gp(void) +{ + atomic_dec(&rcu_expedited_nesting); +} +EXPORT_SYMBOL_GPL(rcu_unexpedite_gp); + +#endif /* #ifndef CONFIG_TINY_RCU */ + +/* + * Inform RCU of the end of the in-kernel boot sequence. + */ +void rcu_end_inkernel_boot(void) +{ + if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT)) + rcu_unexpedite_gp(); +} + +#ifdef CONFIG_PREEMPT_RCU + +/* + * Preemptible RCU implementation for rcu_read_lock(). + * Just increment ->rcu_read_lock_nesting, shared state will be updated + * if we block. + */ +void __rcu_read_lock(void) +{ + current->rcu_read_lock_nesting++; + barrier(); /* critical section after entry code. */ +} +EXPORT_SYMBOL_GPL(__rcu_read_lock); + +/* + * Preemptible RCU implementation for rcu_read_unlock(). + * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost + * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then + * invoke rcu_read_unlock_special() to clean up after a context switch + * in an RCU read-side critical section and other special cases. + */ +void __rcu_read_unlock(void) +{ + struct task_struct *t = current; + + if (t->rcu_read_lock_nesting != 1) { + --t->rcu_read_lock_nesting; + } else { + barrier(); /* critical section before exit code. */ + t->rcu_read_lock_nesting = INT_MIN; + barrier(); /* assign before ->rcu_read_unlock_special load */ + if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special.s))) + rcu_read_unlock_special(t); + barrier(); /* ->rcu_read_unlock_special load before assign */ + t->rcu_read_lock_nesting = 0; + } +#ifdef CONFIG_PROVE_LOCKING + { + int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting); + + WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2); + } +#endif /* #ifdef CONFIG_PROVE_LOCKING */ +} +EXPORT_SYMBOL_GPL(__rcu_read_unlock); + +#endif /* #ifdef CONFIG_PREEMPT_RCU */ + +#ifdef CONFIG_DEBUG_LOCK_ALLOC +static struct lock_class_key rcu_lock_key; +struct lockdep_map rcu_lock_map = + STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); +EXPORT_SYMBOL_GPL(rcu_lock_map); + +static struct lock_class_key rcu_bh_lock_key; +struct lockdep_map rcu_bh_lock_map = + STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); +EXPORT_SYMBOL_GPL(rcu_bh_lock_map); + +static struct lock_class_key rcu_sched_lock_key; +struct lockdep_map rcu_sched_lock_map = + STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); +EXPORT_SYMBOL_GPL(rcu_sched_lock_map); + +static struct lock_class_key rcu_callback_key; +struct lockdep_map rcu_callback_map = + STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key); +EXPORT_SYMBOL_GPL(rcu_callback_map); + +int notrace debug_lockdep_rcu_enabled(void) +{ + return rcu_scheduler_active && debug_locks && + current->lockdep_recursion == 0; +} +EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); + +/** + * rcu_read_lock_held() - might we be in RCU read-side critical section? + * + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU + * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, + * this assumes we are in an RCU read-side critical section unless it can + * prove otherwise. This is useful for debug checks in functions that + * require that they be called within an RCU read-side critical section. + * + * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. + * + * Note that rcu_read_lock() and the matching rcu_read_unlock() must + * occur in the same context, for example, it is illegal to invoke + * rcu_read_unlock() in process context if the matching rcu_read_lock() + * was invoked from within an irq handler. + * + * Note that rcu_read_lock() is disallowed if the CPU is either idle or + * offline from an RCU perspective, so check for those as well. + */ +int rcu_read_lock_held(void) +{ + if (!debug_lockdep_rcu_enabled()) + return 1; + if (!rcu_is_watching()) + return 0; + if (!rcu_lockdep_current_cpu_online()) + return 0; + return lock_is_held(&rcu_lock_map); +} +EXPORT_SYMBOL_GPL(rcu_read_lock_held); + +/** + * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? + * + * Check for bottom half being disabled, which covers both the + * CONFIG_PROVE_RCU and not cases. Note that if someone uses + * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) + * will show the situation. This is useful for debug checks in functions + * that require that they be called within an RCU read-side critical + * section. + * + * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. + * + * Note that rcu_read_lock() is disallowed if the CPU is either idle or + * offline from an RCU perspective, so check for those as well. + */ +int rcu_read_lock_bh_held(void) +{ + if (!debug_lockdep_rcu_enabled()) + return 1; + if (!rcu_is_watching()) + return 0; + if (!rcu_lockdep_current_cpu_online()) + return 0; + return in_softirq() || irqs_disabled(); +} +EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); + +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/** + * wakeme_after_rcu() - Callback function to awaken a task after grace period + * @head: Pointer to rcu_head member within rcu_synchronize structure + * + * Awaken the corresponding task now that a grace period has elapsed. + */ +void wakeme_after_rcu(struct rcu_head *head) +{ + struct rcu_synchronize *rcu; + + rcu = container_of(head, struct rcu_synchronize, head); + complete(&rcu->completion); +} + +void wait_rcu_gp(call_rcu_func_t crf) +{ + struct rcu_synchronize rcu; + + init_rcu_head_on_stack(&rcu.head); + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + crf(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); + destroy_rcu_head_on_stack(&rcu.head); +} +EXPORT_SYMBOL_GPL(wait_rcu_gp); + +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +void init_rcu_head(struct rcu_head *head) +{ + debug_object_init(head, &rcuhead_debug_descr); +} + +void destroy_rcu_head(struct rcu_head *head) +{ + debug_object_free(head, &rcuhead_debug_descr); +} + +/* + * fixup_activate is called when: + * - an active object is activated + * - an unknown object is activated (might be a statically initialized object) + * Activation is performed internally by call_rcu(). + */ +static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state) +{ + struct rcu_head *head = addr; + + switch (state) { + + case ODEBUG_STATE_NOTAVAILABLE: + /* + * This is not really a fixup. We just make sure that it is + * tracked in the object tracker. + */ + debug_object_init(head, &rcuhead_debug_descr); + debug_object_activate(head, &rcuhead_debug_descr); + return 0; + default: + return 1; + } +} + +/** + * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects + * @head: pointer to rcu_head structure to be initialized + * + * This function informs debugobjects of a new rcu_head structure that + * has been allocated as an auto variable on the stack. This function + * is not required for rcu_head structures that are statically defined or + * that are dynamically allocated on the heap. This function has no + * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. + */ +void init_rcu_head_on_stack(struct rcu_head *head) +{ + debug_object_init_on_stack(head, &rcuhead_debug_descr); +} +EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); + +/** + * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects + * @head: pointer to rcu_head structure to be initialized + * + * This function informs debugobjects that an on-stack rcu_head structure + * is about to go out of scope. As with init_rcu_head_on_stack(), this + * function is not required for rcu_head structures that are statically + * defined or that are dynamically allocated on the heap. Also as with + * init_rcu_head_on_stack(), this function has no effect for + * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. + */ +void destroy_rcu_head_on_stack(struct rcu_head *head) +{ + debug_object_free(head, &rcuhead_debug_descr); +} +EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); + +struct debug_obj_descr rcuhead_debug_descr = { + .name = "rcu_head", + .fixup_activate = rcuhead_fixup_activate, +}; +EXPORT_SYMBOL_GPL(rcuhead_debug_descr); +#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ + +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE) +void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, unsigned long c) +{ + trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c); +} +EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); +#else +#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ + do { } while (0) +#endif + +#ifdef CONFIG_RCU_STALL_COMMON + +#ifdef CONFIG_PROVE_RCU +#define RCU_STALL_DELAY_DELTA (5 * HZ) +#else +#define RCU_STALL_DELAY_DELTA 0 +#endif + +int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ +static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; + +module_param(rcu_cpu_stall_suppress, int, 0644); +module_param(rcu_cpu_stall_timeout, int, 0644); + +int rcu_jiffies_till_stall_check(void) +{ + int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout); + + /* + * Limit check must be consistent with the Kconfig limits + * for CONFIG_RCU_CPU_STALL_TIMEOUT. + */ + if (till_stall_check < 3) { + ACCESS_ONCE(rcu_cpu_stall_timeout) = 3; + till_stall_check = 3; + } else if (till_stall_check > 300) { + ACCESS_ONCE(rcu_cpu_stall_timeout) = 300; + till_stall_check = 300; + } + return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; +} + +void rcu_sysrq_start(void) +{ + if (!rcu_cpu_stall_suppress) + rcu_cpu_stall_suppress = 2; +} + +void rcu_sysrq_end(void) +{ + if (rcu_cpu_stall_suppress == 2) + rcu_cpu_stall_suppress = 0; +} + +static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) +{ + rcu_cpu_stall_suppress = 1; + return NOTIFY_DONE; +} + +static struct notifier_block rcu_panic_block = { + .notifier_call = rcu_panic, +}; + +static int __init check_cpu_stall_init(void) +{ + atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); + return 0; +} +early_initcall(check_cpu_stall_init); + +#endif /* #ifdef CONFIG_RCU_STALL_COMMON */ + +#ifdef CONFIG_TASKS_RCU + +/* + * Simple variant of RCU whose quiescent states are voluntary context switch, + * user-space execution, and idle. As such, grace periods can take one good + * long time. There are no read-side primitives similar to rcu_read_lock() + * and rcu_read_unlock() because this implementation is intended to get + * the system into a safe state for some of the manipulations involved in + * tracing and the like. Finally, this implementation does not support + * high call_rcu_tasks() rates from multiple CPUs. If this is required, + * per-CPU callback lists will be needed. + */ + +/* Global list of callbacks and associated lock. */ +static struct rcu_head *rcu_tasks_cbs_head; +static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; +static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq); +static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock); + +/* Track exiting tasks in order to allow them to be waited for. */ +DEFINE_SRCU(tasks_rcu_exit_srcu); + +/* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */ +static int rcu_task_stall_timeout __read_mostly = HZ * 60 * 10; +module_param(rcu_task_stall_timeout, int, 0644); + +static void rcu_spawn_tasks_kthread(void); + +/* + * Post an RCU-tasks callback. First call must be from process context + * after the scheduler if fully operational. + */ +void call_rcu_tasks(struct rcu_head *rhp, void (*func)(struct rcu_head *rhp)) +{ + unsigned long flags; + bool needwake; + + rhp->next = NULL; + rhp->func = func; + raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); + needwake = !rcu_tasks_cbs_head; + *rcu_tasks_cbs_tail = rhp; + rcu_tasks_cbs_tail = &rhp->next; + raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); + if (needwake) { + rcu_spawn_tasks_kthread(); + wake_up(&rcu_tasks_cbs_wq); + } +} +EXPORT_SYMBOL_GPL(call_rcu_tasks); + +/** + * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed. + * + * Control will return to the caller some time after a full rcu-tasks + * grace period has elapsed, in other words after all currently + * executing rcu-tasks read-side critical sections have elapsed. These + * read-side critical sections are delimited by calls to schedule(), + * cond_resched_rcu_qs(), idle execution, userspace execution, calls + * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched(). + * + * This is a very specialized primitive, intended only for a few uses in + * tracing and other situations requiring manipulation of function + * preambles and profiling hooks. The synchronize_rcu_tasks() function + * is not (yet) intended for heavy use from multiple CPUs. + * + * Note that this guarantee implies further memory-ordering guarantees. + * On systems with more than one CPU, when synchronize_rcu_tasks() returns, + * each CPU is guaranteed to have executed a full memory barrier since the + * end of its last RCU-tasks read-side critical section whose beginning + * preceded the call to synchronize_rcu_tasks(). In addition, each CPU + * having an RCU-tasks read-side critical section that extends beyond + * the return from synchronize_rcu_tasks() is guaranteed to have executed + * a full memory barrier after the beginning of synchronize_rcu_tasks() + * and before the beginning of that RCU-tasks read-side critical section. + * Note that these guarantees include CPUs that are offline, idle, or + * executing in user mode, as well as CPUs that are executing in the kernel. + * + * Furthermore, if CPU A invoked synchronize_rcu_tasks(), which returned + * to its caller on CPU B, then both CPU A and CPU B are guaranteed + * to have executed a full memory barrier during the execution of + * synchronize_rcu_tasks() -- even if CPU A and CPU B are the same CPU + * (but again only if the system has more than one CPU). + */ +void synchronize_rcu_tasks(void) +{ + /* Complain if the scheduler has not started. */ + rcu_lockdep_assert(!rcu_scheduler_active, + "synchronize_rcu_tasks called too soon"); + + /* Wait for the grace period. */ + wait_rcu_gp(call_rcu_tasks); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_tasks); + +/** + * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks. + * + * Although the current implementation is guaranteed to wait, it is not + * obligated to, for example, if there are no pending callbacks. + */ +void rcu_barrier_tasks(void) +{ + /* There is only one callback queue, so this is easy. ;-) */ + synchronize_rcu_tasks(); +} +EXPORT_SYMBOL_GPL(rcu_barrier_tasks); + +/* See if tasks are still holding out, complain if so. */ +static void check_holdout_task(struct task_struct *t, + bool needreport, bool *firstreport) +{ + int cpu; + + if (!ACCESS_ONCE(t->rcu_tasks_holdout) || + t->rcu_tasks_nvcsw != ACCESS_ONCE(t->nvcsw) || + !ACCESS_ONCE(t->on_rq) || + (IS_ENABLED(CONFIG_NO_HZ_FULL) && + !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) { + ACCESS_ONCE(t->rcu_tasks_holdout) = false; + list_del_init(&t->rcu_tasks_holdout_list); + put_task_struct(t); + return; + } + if (!needreport) + return; + if (*firstreport) { + pr_err("INFO: rcu_tasks detected stalls on tasks:\n"); + *firstreport = false; + } + cpu = task_cpu(t); + pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n", + t, ".I"[is_idle_task(t)], + "N."[cpu < 0 || !tick_nohz_full_cpu(cpu)], + t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout, + t->rcu_tasks_idle_cpu, cpu); + sched_show_task(t); +} + +/* RCU-tasks kthread that detects grace periods and invokes callbacks. */ +static int __noreturn rcu_tasks_kthread(void *arg) +{ + unsigned long flags; + struct task_struct *g, *t; + unsigned long lastreport; + struct rcu_head *list; + struct rcu_head *next; + LIST_HEAD(rcu_tasks_holdouts); + + /* Run on housekeeping CPUs by default. Sysadm can move if desired. */ + housekeeping_affine(current); + + /* + * Each pass through the following loop makes one check for + * newly arrived callbacks, and, if there are some, waits for + * one RCU-tasks grace period and then invokes the callbacks. + * This loop is terminated by the system going down. ;-) + */ + for (;;) { + + /* Pick up any new callbacks. */ + raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); + list = rcu_tasks_cbs_head; + rcu_tasks_cbs_head = NULL; + rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; + raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); + + /* If there were none, wait a bit and start over. */ + if (!list) { + wait_event_interruptible(rcu_tasks_cbs_wq, + rcu_tasks_cbs_head); + if (!rcu_tasks_cbs_head) { + WARN_ON(signal_pending(current)); + schedule_timeout_interruptible(HZ/10); + } + continue; + } + + /* + * Wait for all pre-existing t->on_rq and t->nvcsw + * transitions to complete. Invoking synchronize_sched() + * suffices because all these transitions occur with + * interrupts disabled. Without this synchronize_sched(), + * a read-side critical section that started before the + * grace period might be incorrectly seen as having started + * after the grace period. + * + * This synchronize_sched() also dispenses with the + * need for a memory barrier on the first store to + * ->rcu_tasks_holdout, as it forces the store to happen + * after the beginning of the grace period. + */ + synchronize_sched(); + + /* + * There were callbacks, so we need to wait for an + * RCU-tasks grace period. Start off by scanning + * the task list for tasks that are not already + * voluntarily blocked. Mark these tasks and make + * a list of them in rcu_tasks_holdouts. + */ + rcu_read_lock(); + for_each_process_thread(g, t) { + if (t != current && ACCESS_ONCE(t->on_rq) && + !is_idle_task(t)) { + get_task_struct(t); + t->rcu_tasks_nvcsw = ACCESS_ONCE(t->nvcsw); + ACCESS_ONCE(t->rcu_tasks_holdout) = true; + list_add(&t->rcu_tasks_holdout_list, + &rcu_tasks_holdouts); + } + } + rcu_read_unlock(); + + /* + * Wait for tasks that are in the process of exiting. + * This does only part of the job, ensuring that all + * tasks that were previously exiting reach the point + * where they have disabled preemption, allowing the + * later synchronize_sched() to finish the job. + */ + synchronize_srcu(&tasks_rcu_exit_srcu); + + /* + * Each pass through the following loop scans the list + * of holdout tasks, removing any that are no longer + * holdouts. When the list is empty, we are done. + */ + lastreport = jiffies; + while (!list_empty(&rcu_tasks_holdouts)) { + bool firstreport; + bool needreport; + int rtst; + struct task_struct *t1; + + schedule_timeout_interruptible(HZ); + rtst = ACCESS_ONCE(rcu_task_stall_timeout); + needreport = rtst > 0 && + time_after(jiffies, lastreport + rtst); + if (needreport) + lastreport = jiffies; + firstreport = true; + WARN_ON(signal_pending(current)); + list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts, + rcu_tasks_holdout_list) { + check_holdout_task(t, needreport, &firstreport); + cond_resched(); + } + } + + /* + * Because ->on_rq and ->nvcsw are not guaranteed + * to have a full memory barriers prior to them in the + * schedule() path, memory reordering on other CPUs could + * cause their RCU-tasks read-side critical sections to + * extend past the end of the grace period. However, + * because these ->nvcsw updates are carried out with + * interrupts disabled, we can use synchronize_sched() + * to force the needed ordering on all such CPUs. + * + * This synchronize_sched() also confines all + * ->rcu_tasks_holdout accesses to be within the grace + * period, avoiding the need for memory barriers for + * ->rcu_tasks_holdout accesses. + * + * In addition, this synchronize_sched() waits for exiting + * tasks to complete their final preempt_disable() region + * of execution, cleaning up after the synchronize_srcu() + * above. + */ + synchronize_sched(); + + /* Invoke the callbacks. */ + while (list) { + next = list->next; + local_bh_disable(); + list->func(list); + local_bh_enable(); + list = next; + cond_resched(); + } + schedule_timeout_uninterruptible(HZ/10); + } +} + +/* Spawn rcu_tasks_kthread() at first call to call_rcu_tasks(). */ +static void rcu_spawn_tasks_kthread(void) +{ + static DEFINE_MUTEX(rcu_tasks_kthread_mutex); + static struct task_struct *rcu_tasks_kthread_ptr; + struct task_struct *t; + + if (ACCESS_ONCE(rcu_tasks_kthread_ptr)) { + smp_mb(); /* Ensure caller sees full kthread. */ + return; + } + mutex_lock(&rcu_tasks_kthread_mutex); + if (rcu_tasks_kthread_ptr) { + mutex_unlock(&rcu_tasks_kthread_mutex); + return; + } + t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread"); + BUG_ON(IS_ERR(t)); + smp_mb(); /* Ensure others see full kthread. */ + ACCESS_ONCE(rcu_tasks_kthread_ptr) = t; + mutex_unlock(&rcu_tasks_kthread_mutex); +} + +#endif /* #ifdef CONFIG_TASKS_RCU */ + +#ifdef CONFIG_PROVE_RCU + +/* + * Early boot self test parameters, one for each flavor + */ +static bool rcu_self_test; +static bool rcu_self_test_bh; +static bool rcu_self_test_sched; + +module_param(rcu_self_test, bool, 0444); +module_param(rcu_self_test_bh, bool, 0444); +module_param(rcu_self_test_sched, bool, 0444); + +static int rcu_self_test_counter; + +static void test_callback(struct rcu_head *r) +{ + rcu_self_test_counter++; + pr_info("RCU test callback executed %d\n", rcu_self_test_counter); +} + +static void early_boot_test_call_rcu(void) +{ + static struct rcu_head head; + + call_rcu(&head, test_callback); +} + +static void early_boot_test_call_rcu_bh(void) +{ + static struct rcu_head head; + + call_rcu_bh(&head, test_callback); +} + +static void early_boot_test_call_rcu_sched(void) +{ + static struct rcu_head head; + + call_rcu_sched(&head, test_callback); +} + +void rcu_early_boot_tests(void) +{ + pr_info("Running RCU self tests\n"); + + if (rcu_self_test) + early_boot_test_call_rcu(); + if (rcu_self_test_bh) + early_boot_test_call_rcu_bh(); + if (rcu_self_test_sched) + early_boot_test_call_rcu_sched(); +} + +static int rcu_verify_early_boot_tests(void) +{ + int ret = 0; + int early_boot_test_counter = 0; + + if (rcu_self_test) { + early_boot_test_counter++; + rcu_barrier(); + } + if (rcu_self_test_bh) { + early_boot_test_counter++; + rcu_barrier_bh(); + } + if (rcu_self_test_sched) { + early_boot_test_counter++; + rcu_barrier_sched(); + } + + if (rcu_self_test_counter != early_boot_test_counter) { + WARN_ON(1); + ret = -1; + } + + return ret; +} +late_initcall(rcu_verify_early_boot_tests); +#else +void rcu_early_boot_tests(void) {} +#endif /* CONFIG_PROVE_RCU */ |