211 lines
7.1 KiB
C
211 lines
7.1 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, you can access it online at
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* http://www.gnu.org/licenses/gpl-2.0.html.
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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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#include <linux/rcu_segcblist.h>
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struct srcu_struct;
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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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#ifdef CONFIG_TINY_SRCU
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#include <linux/srcutiny.h>
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#elif defined(CONFIG_TREE_SRCU)
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#include <linux/srcutree.h>
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#elif defined(CONFIG_CLASSIC_SRCU)
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#include <linux/srcuclassic.h>
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#else
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#error "Unknown SRCU implementation specified to kernel configuration"
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#endif
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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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#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 SRCU is based on its own statemachine and it doesn't
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* relies on normal RCU, it can be called from the CPU which
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* is in the idle loop from an RCU point of view or 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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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), (c) || srcu_read_lock_held(sp), __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;
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preempt_disable();
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retval = __srcu_read_lock(sp);
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preempt_enable();
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rcu_lock_acquire(&(sp)->dep_map);
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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_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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* smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
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*
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* Converts the preceding srcu_read_unlock into a two-way memory barrier.
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*
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* Call this after srcu_read_unlock, to guarantee that all memory operations
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* that occur after smp_mb__after_srcu_read_unlock will appear to happen after
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* the preceding srcu_read_unlock.
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*/
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static inline void smp_mb__after_srcu_read_unlock(void)
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{
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/* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
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}
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#endif
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