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Diffstat (limited to 'include/linux/srcu.h')
| -rw-r--r-- | include/linux/srcu.h | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h new file mode 100644 index 000000000..bdeb4567b --- /dev/null +++ b/include/linux/srcu.h @@ -0,0 +1,252 @@ +/* + * 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 + * + */ + +#ifndef _LINUX_SRCU_H +#define _LINUX_SRCU_H + +#include <linux/mutex.h> +#include <linux/rcupdate.h> +#include <linux/workqueue.h> + +struct srcu_struct_array { + unsigned long c[2]; + unsigned long seq[2]; +}; + +struct rcu_batch { + struct rcu_head *head, **tail; +}; + +#define RCU_BATCH_INIT(name) { NULL, &(name.head) } + +struct srcu_struct { + unsigned long completed; + struct srcu_struct_array __percpu *per_cpu_ref; + spinlock_t queue_lock; /* protect ->batch_queue, ->running */ + bool running; + /* callbacks just queued */ + struct rcu_batch batch_queue; + /* callbacks try to do the first check_zero */ + struct rcu_batch batch_check0; + /* callbacks done with the first check_zero and the flip */ + struct rcu_batch batch_check1; + struct rcu_batch batch_done; + struct delayed_work work; +#ifdef CONFIG_DEBUG_LOCK_ALLOC + struct lockdep_map dep_map; +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ +}; + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +int __init_srcu_struct(struct srcu_struct *sp, const char *name, + struct lock_class_key *key); + +#define init_srcu_struct(sp) \ +({ \ + static struct lock_class_key __srcu_key; \ + \ + __init_srcu_struct((sp), #sp, &__srcu_key); \ +}) + +#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +int init_srcu_struct(struct srcu_struct *sp); + +#define __SRCU_DEP_MAP_INIT(srcu_name) +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +void process_srcu(struct work_struct *work); + +#define __SRCU_STRUCT_INIT(name) \ + { \ + .completed = -300, \ + .per_cpu_ref = &name##_srcu_array, \ + .queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \ + .running = false, \ + .batch_queue = RCU_BATCH_INIT(name.batch_queue), \ + .batch_check0 = RCU_BATCH_INIT(name.batch_check0), \ + .batch_check1 = RCU_BATCH_INIT(name.batch_check1), \ + .batch_done = RCU_BATCH_INIT(name.batch_done), \ + .work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\ + __SRCU_DEP_MAP_INIT(name) \ + } + +/* + * define and init a srcu struct at build time. + * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it. + */ +#define __DEFINE_SRCU(name, is_static) \ + static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\ + is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name) +#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */) +#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static) + +/** + * call_srcu() - Queue a callback for invocation after an SRCU grace period + * @sp: srcu_struct in queue the callback + * @head: structure to be used for queueing the SRCU callback. + * @func: function to be invoked after the SRCU grace period + * + * The callback function will be invoked some time after a full SRCU + * grace period elapses, in other words after all pre-existing SRCU + * read-side critical sections have completed. However, the callback + * function might well execute concurrently with other SRCU read-side + * critical sections that started after call_srcu() was invoked. SRCU + * read-side critical sections are delimited by srcu_read_lock() and + * srcu_read_unlock(), and may be nested. + * + * The callback will be invoked from process context, but must nevertheless + * be fast and must not block. + */ +void call_srcu(struct srcu_struct *sp, struct rcu_head *head, + void (*func)(struct rcu_head *head)); + +void cleanup_srcu_struct(struct srcu_struct *sp); +int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); +void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); +void synchronize_srcu(struct srcu_struct *sp); +void synchronize_srcu_expedited(struct srcu_struct *sp); +unsigned long srcu_batches_completed(struct srcu_struct *sp); +void srcu_barrier(struct srcu_struct *sp); + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +/** + * srcu_read_lock_held - might we be in SRCU read-side critical section? + * + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU + * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, + * this assumes we are in an SRCU read-side critical section unless it can + * prove otherwise. + * + * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. + * + * Note that SRCU is based on its own statemachine and it doesn't + * relies on normal RCU, it can be called from the CPU which + * is in the idle loop from an RCU point of view or offline. + */ +static inline int srcu_read_lock_held(struct srcu_struct *sp) +{ + if (!debug_lockdep_rcu_enabled()) + return 1; + return lock_is_held(&sp->dep_map); +} + +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +static inline int srcu_read_lock_held(struct srcu_struct *sp) +{ + return 1; +} + +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +/** + * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing + * @p: the pointer to fetch and protect for later dereferencing + * @sp: pointer to the srcu_struct, which is used to check that we + * really are in an SRCU read-side critical section. + * @c: condition to check for update-side use + * + * If PROVE_RCU is enabled, invoking this outside of an RCU read-side + * critical section will result in an RCU-lockdep splat, unless @c evaluates + * to 1. The @c argument will normally be a logical expression containing + * lockdep_is_held() calls. + */ +#define srcu_dereference_check(p, sp, c) \ + __rcu_dereference_check((p), (c) || srcu_read_lock_held(sp), __rcu) + +/** + * srcu_dereference - fetch SRCU-protected pointer for later dereferencing + * @p: the pointer to fetch and protect for later dereferencing + * @sp: pointer to the srcu_struct, which is used to check that we + * really are in an SRCU read-side critical section. + * + * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU + * is enabled, invoking this outside of an RCU read-side critical + * section will result in an RCU-lockdep splat. + */ +#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) + +/** + * srcu_read_lock - register a new reader for an SRCU-protected structure. + * @sp: srcu_struct in which to register the new reader. + * + * Enter an SRCU read-side critical section. Note that SRCU read-side + * critical sections may be nested. However, it is illegal to + * call anything that waits on an SRCU grace period for the same + * srcu_struct, whether directly or indirectly. Please note that + * one way to indirectly wait on an SRCU grace period is to acquire + * a mutex that is held elsewhere while calling synchronize_srcu() or + * synchronize_srcu_expedited(). + * + * Note that srcu_read_lock() and the matching srcu_read_unlock() must + * occur in the same context, for example, it is illegal to invoke + * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() + * was invoked in process context. + */ +static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) +{ + int retval = __srcu_read_lock(sp); + + rcu_lock_acquire(&(sp)->dep_map); + return retval; +} + +/** + * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. + * @sp: srcu_struct in which to unregister the old reader. + * @idx: return value from corresponding srcu_read_lock(). + * + * Exit an SRCU read-side critical section. + */ +static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) + __releases(sp) +{ + rcu_lock_release(&(sp)->dep_map); + __srcu_read_unlock(sp, idx); +} + +/** + * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock + * + * Converts the preceding srcu_read_unlock into a two-way memory barrier. + * + * Call this after srcu_read_unlock, to guarantee that all memory operations + * that occur after smp_mb__after_srcu_read_unlock will appear to happen after + * the preceding srcu_read_unlock. + */ +static inline void smp_mb__after_srcu_read_unlock(void) +{ + /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ +} + +#endif |