| /* |
| * 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 initialize a srcu struct at build time. |
| * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it. |
| * |
| * Note that although DEFINE_STATIC_SRCU() hides the name from other |
| * files, the per-CPU variable rules nevertheless require that the |
| * chosen name be globally unique. These rules also prohibit use of |
| * DEFINE_STATIC_SRCU() within a function. If these rules are too |
| * restrictive, declare the srcu_struct manually. For example, in |
| * each file: |
| * |
| * static struct srcu_struct my_srcu; |
| * |
| * Then, before the first use of each my_srcu, manually initialize it: |
| * |
| * init_srcu_struct(&my_srcu); |
| * |
| * See include/linux/percpu-defs.h for the rules on per-CPU variables. |
| */ |
| #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; |
| |
| preempt_disable(); |
| retval = __srcu_read_lock(sp); |
| preempt_enable(); |
| 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 |