304 строки
11 KiB
C
304 строки
11 KiB
C
/*
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* Sleepable Read-Copy Update mechanism for mutual exclusion
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2006
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* Copyright (C) Fujitsu, 2012
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*
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* Author: Paul McKenney <paulmck@us.ibm.com>
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* Lai Jiangshan <laijs@cn.fujitsu.com>
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU/ *.txt
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*
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*/
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#ifndef _LINUX_SRCU_H
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#define _LINUX_SRCU_H
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#include <linux/mutex.h>
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#include <linux/rcupdate.h>
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#include <linux/workqueue.h>
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struct srcu_struct_array {
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unsigned long c[2];
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unsigned long seq[2];
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};
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struct rcu_batch {
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struct rcu_head *head, **tail;
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};
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#define RCU_BATCH_INIT(name) { NULL, &(name.head) }
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struct srcu_struct {
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unsigned completed;
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struct srcu_struct_array __percpu *per_cpu_ref;
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spinlock_t queue_lock; /* protect ->batch_queue, ->running */
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bool running;
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/* callbacks just queued */
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struct rcu_batch batch_queue;
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/* callbacks try to do the first check_zero */
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struct rcu_batch batch_check0;
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/* callbacks done with the first check_zero and the flip */
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struct rcu_batch batch_check1;
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struct rcu_batch batch_done;
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struct delayed_work work;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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};
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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int __init_srcu_struct(struct srcu_struct *sp, const char *name,
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struct lock_class_key *key);
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#define init_srcu_struct(sp) \
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({ \
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static struct lock_class_key __srcu_key; \
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\
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__init_srcu_struct((sp), #sp, &__srcu_key); \
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})
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#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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int init_srcu_struct(struct srcu_struct *sp);
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#define __SRCU_DEP_MAP_INIT(srcu_name)
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#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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void process_srcu(struct work_struct *work);
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#define __SRCU_STRUCT_INIT(name) \
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{ \
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.completed = -300, \
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.per_cpu_ref = &name##_srcu_array, \
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.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
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.running = false, \
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.batch_queue = RCU_BATCH_INIT(name.batch_queue), \
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.batch_check0 = RCU_BATCH_INIT(name.batch_check0), \
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.batch_check1 = RCU_BATCH_INIT(name.batch_check1), \
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.batch_done = RCU_BATCH_INIT(name.batch_done), \
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.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
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__SRCU_DEP_MAP_INIT(name) \
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}
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/*
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* define and init a srcu struct at build time.
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* dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
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*/
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#define DEFINE_SRCU(name) \
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static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
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struct srcu_struct name = __SRCU_STRUCT_INIT(name);
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#define DEFINE_STATIC_SRCU(name) \
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static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
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static struct srcu_struct name = __SRCU_STRUCT_INIT(name);
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/**
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* call_srcu() - Queue a callback for invocation after an SRCU grace period
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* @sp: srcu_struct in queue the callback
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* @head: structure to be used for queueing the SRCU callback.
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* @func: function to be invoked after the SRCU grace period
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*
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* The callback function will be invoked some time after a full SRCU
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* grace period elapses, in other words after all pre-existing SRCU
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* read-side critical sections have completed. However, the callback
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* function might well execute concurrently with other SRCU read-side
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* critical sections that started after call_srcu() was invoked. SRCU
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* read-side critical sections are delimited by srcu_read_lock() and
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* srcu_read_unlock(), and may be nested.
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*
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* The callback will be invoked from process context, but must nevertheless
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* be fast and must not block.
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*/
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void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
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void (*func)(struct rcu_head *head));
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void cleanup_srcu_struct(struct srcu_struct *sp);
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int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
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void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
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void synchronize_srcu(struct srcu_struct *sp);
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void synchronize_srcu_expedited(struct srcu_struct *sp);
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long srcu_batches_completed(struct srcu_struct *sp);
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void srcu_barrier(struct srcu_struct *sp);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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/**
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* srcu_read_lock_held - might we be in SRCU read-side critical section?
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*
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* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
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* read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
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* this assumes we are in an SRCU read-side critical section unless it can
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* prove otherwise.
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*
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* Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
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* and while lockdep is disabled.
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*
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* Note that if the CPU is in the idle loop from an RCU point of view
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* (ie: that we are in the section between rcu_idle_enter() and
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* rcu_idle_exit()) then srcu_read_lock_held() returns false even if
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* the CPU did an srcu_read_lock(). The reason for this is that RCU
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* ignores CPUs that are in such a section, considering these as in
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* extended quiescent state, so such a CPU is effectively never in an
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* RCU read-side critical section regardless of what RCU primitives it
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* invokes. This state of affairs is required --- we need to keep an
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* RCU-free window in idle where the CPU may possibly enter into low
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* power mode. This way we can notice an extended quiescent state to
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* other CPUs that started a grace period. Otherwise we would delay any
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* grace period as long as we run in the idle task.
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*
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* Similarly, we avoid claiming an SRCU read lock held if the current
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* CPU is offline.
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*/
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static inline int srcu_read_lock_held(struct srcu_struct *sp)
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{
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if (!debug_lockdep_rcu_enabled())
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return 1;
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if (rcu_is_cpu_idle())
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return 0;
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if (!rcu_lockdep_current_cpu_online())
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return 0;
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return lock_is_held(&sp->dep_map);
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}
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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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static inline int srcu_read_lock_held(struct srcu_struct *sp)
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{
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return 1;
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}
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#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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/**
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* srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
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* @p: the pointer to fetch and protect for later dereferencing
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* @sp: pointer to the srcu_struct, which is used to check that we
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* really are in an SRCU read-side critical section.
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* @c: condition to check for update-side use
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*
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* If PROVE_RCU is enabled, invoking this outside of an RCU read-side
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* critical section will result in an RCU-lockdep splat, unless @c evaluates
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* to 1. The @c argument will normally be a logical expression containing
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* lockdep_is_held() calls.
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*/
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#define srcu_dereference_check(p, sp, c) \
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__rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu)
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/**
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* srcu_dereference - fetch SRCU-protected pointer for later dereferencing
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* @p: the pointer to fetch and protect for later dereferencing
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* @sp: pointer to the srcu_struct, which is used to check that we
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* really are in an SRCU read-side critical section.
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*
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* Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
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* is enabled, invoking this outside of an RCU read-side critical
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* section will result in an RCU-lockdep splat.
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*/
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#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
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/**
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* srcu_read_lock - register a new reader for an SRCU-protected structure.
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* @sp: srcu_struct in which to register the new reader.
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*
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* Enter an SRCU read-side critical section. Note that SRCU read-side
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* critical sections may be nested. However, it is illegal to
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* call anything that waits on an SRCU grace period for the same
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* srcu_struct, whether directly or indirectly. Please note that
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* one way to indirectly wait on an SRCU grace period is to acquire
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* a mutex that is held elsewhere while calling synchronize_srcu() or
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* synchronize_srcu_expedited().
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*
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* Note that srcu_read_lock() and the matching srcu_read_unlock() must
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* occur in the same context, for example, it is illegal to invoke
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* srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
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* was invoked in process context.
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*/
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static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
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{
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int retval = __srcu_read_lock(sp);
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rcu_lock_acquire(&(sp)->dep_map);
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rcu_lockdep_assert(!rcu_is_cpu_idle(),
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"srcu_read_lock() used illegally while idle");
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return retval;
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}
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/**
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* srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
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* @sp: srcu_struct in which to unregister the old reader.
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* @idx: return value from corresponding srcu_read_lock().
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*
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* Exit an SRCU read-side critical section.
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*/
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static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
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__releases(sp)
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{
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rcu_lockdep_assert(!rcu_is_cpu_idle(),
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"srcu_read_unlock() used illegally while idle");
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rcu_lock_release(&(sp)->dep_map);
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__srcu_read_unlock(sp, idx);
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}
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/**
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* srcu_read_lock_raw - register a new reader for an SRCU-protected structure.
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* @sp: srcu_struct in which to register the new reader.
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*
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* Enter an SRCU read-side critical section. Similar to srcu_read_lock(),
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* but avoids the RCU-lockdep checking. This means that it is legal to
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* use srcu_read_lock_raw() in one context, for example, in an exception
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* handler, and then have the matching srcu_read_unlock_raw() in another
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* context, for example in the task that took the exception.
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*
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* However, the entire SRCU read-side critical section must reside within a
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* single task. For example, beware of using srcu_read_lock_raw() in
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* a device interrupt handler and srcu_read_unlock() in the interrupted
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* task: This will not work if interrupts are threaded.
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*/
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static inline int srcu_read_lock_raw(struct srcu_struct *sp)
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{
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unsigned long flags;
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int ret;
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local_irq_save(flags);
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ret = __srcu_read_lock(sp);
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local_irq_restore(flags);
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return ret;
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}
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/**
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* srcu_read_unlock_raw - unregister reader from an SRCU-protected structure.
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* @sp: srcu_struct in which to unregister the old reader.
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* @idx: return value from corresponding srcu_read_lock_raw().
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*
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* Exit an SRCU read-side critical section without lockdep-RCU checking.
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* See srcu_read_lock_raw() for more details.
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*/
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static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx)
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{
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unsigned long flags;
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local_irq_save(flags);
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__srcu_read_unlock(sp, idx);
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local_irq_restore(flags);
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}
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#endif
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