include/linux/srcu.h - linux-mtk - Git at Google

 /*
  * 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>
 #include <linux/rcu_segcblist.h>

 struct srcu_struct;

 #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 */

 #ifdef CONFIG_TINY_SRCU
 #include <linux/srcutiny.h>
 #elif defined(CONFIG_TREE_SRCU)
 #include <linux/srcutree.h>
 #elif defined(CONFIG_SRCU)
 #error "Unknown SRCU implementation specified to kernel configuration"
 #else
 /* Dummy definition for things like notifiers.  Actual use gets link error. */
 struct srcu_struct { };
 #endif

 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, bool quiesced);
 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);

 /**
  * 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.
  */
 static inline void cleanup_srcu_struct(struct srcu_struct *sp)
 {
 	_cleanup_srcu_struct(sp, false);
 }

 /**
  * cleanup_srcu_struct_quiesced - deconstruct a quiesced 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.  Also,
  * all grace-period processing must have completed.
  *
  * "Completed" means that the last synchronize_srcu() and
  * synchronize_srcu_expedited() calls must have returned before the call
  * to cleanup_srcu_struct_quiesced().  It also means that the callback
  * from the last call_srcu() must have been invoked before the call to
  * cleanup_srcu_struct_quiesced(), but you can use srcu_barrier() to help
  * with this last.  Violating these rules will get you a WARN_ON() splat
  * (with high probability, anyway), and will also cause the srcu_struct
  * to be leaked.
  */
 static inline void cleanup_srcu_struct_quiesced(struct srcu_struct *sp)
 {
 	_cleanup_srcu_struct(sp, true);
 }

 #ifdef CONFIG_DEBUG_LOCK_ALLOC

 /**
  * srcu_read_lock_held - might we be in SRCU read-side critical section?
  * @sp: The srcu_struct structure to check
  *
  * 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(const 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(const 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_dereference_notrace - no tracing and no lockdep calls from here
  */
 #define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1)

 /**
  * 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;

 	retval = __srcu_read_lock(sp);
 	rcu_lock_acquire(&(sp)->dep_map);
 	return retval;
 }

 /* Used by tracing, cannot be traced and cannot invoke lockdep. */
 static inline notrace int
 srcu_read_lock_notrace(struct srcu_struct *sp) __acquires(sp)
 {
 	int retval;

 	retval = __srcu_read_lock(sp);
 	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);
 }

 /* Used by tracing, cannot be traced and cannot call lockdep. */
 static inline notrace void
 srcu_read_unlock_notrace(struct srcu_struct *sp, int idx) __releases(sp)
 {
 	__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
	/*
	* 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>
	#include <linux/rcu_segcblist.h>

	struct srcu_struct;

	#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 */

	#ifdef CONFIG_TINY_SRCU
	#include <linux/srcutiny.h>
	#elif defined(CONFIG_TREE_SRCU)
	#include <linux/srcutree.h>
	#elif defined(CONFIG_SRCU)
	#error "Unknown SRCU implementation specified to kernel configuration"
	#else
	/* Dummy definition for things like notifiers. Actual use gets link error. */
	struct srcu_struct { };
	#endif

	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, bool quiesced);
	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);

	/**
	* 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.
	*/
	static inline void cleanup_srcu_struct(struct srcu_struct *sp)
	{
	_cleanup_srcu_struct(sp, false);
	}

	/**
	* cleanup_srcu_struct_quiesced - deconstruct a quiesced 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. Also,
	* all grace-period processing must have completed.
	*
	* "Completed" means that the last synchronize_srcu() and
	* synchronize_srcu_expedited() calls must have returned before the call
	* to cleanup_srcu_struct_quiesced(). It also means that the callback
	* from the last call_srcu() must have been invoked before the call to
	* cleanup_srcu_struct_quiesced(), but you can use srcu_barrier() to help
	* with this last. Violating these rules will get you a WARN_ON() splat
	* (with high probability, anyway), and will also cause the srcu_struct
	* to be leaked.
	*/
	static inline void cleanup_srcu_struct_quiesced(struct srcu_struct *sp)
	{
	_cleanup_srcu_struct(sp, true);
	}

	#ifdef CONFIG_DEBUG_LOCK_ALLOC

	/**
	* srcu_read_lock_held - might we be in SRCU read-side critical section?
	* @sp: The srcu_struct structure to check
	*
	* 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(const 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(const 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_dereference_notrace - no tracing and no lockdep calls from here
	*/
	#define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1)

	/**
	* 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;

	retval = __srcu_read_lock(sp);
	rcu_lock_acquire(&(sp)->dep_map);
	return retval;
	}

	/* Used by tracing, cannot be traced and cannot invoke lockdep. */
	static inline notrace int
	srcu_read_lock_notrace(struct srcu_struct *sp) __acquires(sp)
	{
	int retval;

	retval = __srcu_read_lock(sp);
	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);
	}

	/* Used by tracing, cannot be traced and cannot call lockdep. */
	static inline notrace void
	srcu_read_unlock_notrace(struct srcu_struct *sp, int idx) __releases(sp)
	{
	__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