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-rw-r--r--kernel/rcu/Makefile7
-rw-r--r--kernel/rcu/rcu.h146
-rw-r--r--kernel/rcu/rcutorture.c1861
-rw-r--r--kernel/rcu/srcu.c676
-rw-r--r--kernel/rcu/tiny.c288
-rw-r--r--kernel/rcu/tiny_plugin.h173
-rw-r--r--kernel/rcu/tree.c4136
-rw-r--r--kernel/rcu/tree.h620
-rw-r--r--kernel/rcu/tree_plugin.h3090
-rw-r--r--kernel/rcu/tree_trace.c505
-rw-r--r--kernel/rcu/update.c831
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(&current->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 */