[linux.git] / kernel / rcupdate.c

/*
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright IBM Corporation, 2001
 *
 * Authors: Dipankar Sarma <[email protected]>
 *	    Manfred Spraul <[email protected]>
 *
 * Based on the original work by Paul McKenney <[email protected]>
 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
 * Papers:
 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
 *
 * For detailed explanation of Read-Copy Update mechanism see -
 *		http://lse.sourceforge.net/locking/rcupdate.html
 *
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <asm/atomic.h>
#include <linux/bitops.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/hardirq.h>

#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
struct lockdep_map rcu_lock_map =
	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
EXPORT_SYMBOL_GPL(rcu_lock_map);

static struct lock_class_key rcu_bh_lock_key;
struct lockdep_map rcu_bh_lock_map =
	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
EXPORT_SYMBOL_GPL(rcu_bh_lock_map);

static struct lock_class_key rcu_sched_lock_key;
struct lockdep_map rcu_sched_lock_map =
	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
#endif

#ifdef CONFIG_DEBUG_LOCK_ALLOC

int debug_lockdep_rcu_enabled(void)
{
	return rcu_scheduler_active && debug_locks &&
	       current->lockdep_recursion == 0;
}
EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);

/**
 * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
 *
 * Check for bottom half being disabled, which covers both the
 * CONFIG_PROVE_RCU and not cases.  Note that if someone uses
 * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
 * will show the situation.  This is useful for debug checks in functions
 * that require that they be called within an RCU read-side critical
 * section.
 *
 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
 */
int rcu_read_lock_bh_held(void)
{
	if (!debug_lockdep_rcu_enabled())
		return 1;
	return in_softirq() || irqs_disabled();
}
EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);

#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

/*
 * Awaken the corresponding synchronize_rcu() instance now that a
 * grace period has elapsed.
 */
void wakeme_after_rcu(struct rcu_head  *head)
{
	struct rcu_synchronize *rcu;

	rcu = container_of(head, struct rcu_synchronize, head);
	complete(&rcu->completion);
}

#ifdef CONFIG_PROVE_RCU
/*
 * wrapper function to avoid #include problems.
 */
int rcu_my_thread_group_empty(void)
{
	return thread_group_empty(current);
}
EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
#endif /* #ifdef CONFIG_PROVE_RCU */

#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
static inline void debug_init_rcu_head(struct rcu_head *head)
{
	debug_object_init(head, &rcuhead_debug_descr);
}

static inline void debug_rcu_head_free(struct rcu_head *head)
{
	debug_object_free(head, &rcuhead_debug_descr);
}

/*
 * fixup_init is called when:
 * - an active object is initialized
 */
static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
{
	struct rcu_head *head = addr;

	switch (state) {
	case ODEBUG_STATE_ACTIVE:
		/*
		 * Ensure that queued callbacks are all executed.
		 * If we detect that we are nested in a RCU read-side critical
		 * section, we should simply fail, otherwise we would deadlock.
		 */
		if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
		    irqs_disabled()) {
			WARN_ON(1);
			return 0;
		}
		rcu_barrier();
		rcu_barrier_sched();
		rcu_barrier_bh();
		debug_object_init(head, &rcuhead_debug_descr);
		return 1;
	default:
		return 0;
	}
}

/*
 * fixup_activate is called when:
 * - an active object is activated
 * - an unknown object is activated (might be a statically initialized object)
 * Activation is performed internally by call_rcu().
 */
static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
{
	struct rcu_head *head = addr;

	switch (state) {

	case ODEBUG_STATE_NOTAVAILABLE:
		/*
		 * This is not really a fixup. We just make sure that it is
		 * tracked in the object tracker.
		 */
		debug_object_init(head, &rcuhead_debug_descr);
		debug_object_activate(head, &rcuhead_debug_descr);
		return 0;

	case ODEBUG_STATE_ACTIVE:
		/*
		 * Ensure that queued callbacks are all executed.
		 * If we detect that we are nested in a RCU read-side critical
		 * section, we should simply fail, otherwise we would deadlock.
		 */
		if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
		    irqs_disabled()) {
			WARN_ON(1);
			return 0;
		}
		rcu_barrier();
		rcu_barrier_sched();
		rcu_barrier_bh();
		debug_object_activate(head, &rcuhead_debug_descr);
		return 1;
	default:
		return 0;
	}
}

/*
 * fixup_free is called when:
 * - an active object is freed
 */
static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
{
	struct rcu_head *head = addr;

	switch (state) {
	case ODEBUG_STATE_ACTIVE:
		/*
		 * Ensure that queued callbacks are all executed.
		 * If we detect that we are nested in a RCU read-side critical
		 * section, we should simply fail, otherwise we would deadlock.
		 * Note that the machinery to reliably determine whether
		 * or not we are in an RCU read-side critical section
		 * exists only in the preemptible RCU implementations
		 * (TINY_PREEMPT_RCU and TREE_PREEMPT_RCU), which is why
		 * DEBUG_OBJECTS_RCU_HEAD is disallowed if !PREEMPT.
		 */
		if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
		    irqs_disabled()) {
			WARN_ON(1);
			return 0;
		}
		rcu_barrier();
		rcu_barrier_sched();
		rcu_barrier_bh();
		debug_object_free(head, &rcuhead_debug_descr);
		return 1;
	default:
		return 0;
	}
}

/**
 * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
 * @head: pointer to rcu_head structure to be initialized
 *
 * This function informs debugobjects of a new rcu_head structure that
 * has been allocated as an auto variable on the stack.  This function
 * is not required for rcu_head structures that are statically defined or
 * that are dynamically allocated on the heap.  This function has no
 * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
 */
void init_rcu_head_on_stack(struct rcu_head *head)
{
	debug_object_init_on_stack(head, &rcuhead_debug_descr);
}
EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);

/**
 * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
 * @head: pointer to rcu_head structure to be initialized
 *
 * This function informs debugobjects that an on-stack rcu_head structure
 * is about to go out of scope.  As with init_rcu_head_on_stack(), this
 * function is not required for rcu_head structures that are statically
 * defined or that are dynamically allocated on the heap.  Also as with
 * init_rcu_head_on_stack(), this function has no effect for
 * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
 */
void destroy_rcu_head_on_stack(struct rcu_head *head)
{
	debug_object_free(head, &rcuhead_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);

struct debug_obj_descr rcuhead_debug_descr = {
	.name = "rcu_head",
	.fixup_init = rcuhead_fixup_init,
	.fixup_activate = rcuhead_fixup_activate,
	.fixup_free = rcuhead_fixup_free,
};
EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Read-Copy Update mechanism for mutual exclusion
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; if not, write to the Free Software
	16	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	17	*
01c1c660	18	* Copyright IBM Corporation, 2001
1da177e4 LT	19	*
	20	* Authors: Dipankar Sarma <[email protected]>
	21	* Manfred Spraul <[email protected]>
a71fca58	22	*
1da177e4 LT	23	* Based on the original work by Paul McKenney <[email protected]>
	24	* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
	25	* Papers:
	26	* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
	27	* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
	28	*
	29	* For detailed explanation of Read-Copy Update mechanism see -
a71fca58	30	* http://lse.sourceforge.net/locking/rcupdate.html
1da177e4 LT	31	*
	32	*/
	33	#include <linux/types.h>
	34	#include <linux/kernel.h>
	35	#include <linux/init.h>
	36	#include <linux/spinlock.h>
	37	#include <linux/smp.h>
	38	#include <linux/interrupt.h>
	39	#include <linux/sched.h>
	40	#include <asm/atomic.h>
	41	#include <linux/bitops.h>
1da177e4 LT	42	#include <linux/percpu.h>
1da177e4 LT	43	#include <linux/notifier.h>
1da177e4	44	#include <linux/cpu.h>
9331b315	45	#include <linux/mutex.h>
01c1c660	46	#include <linux/module.h>
e3818b8d	47	#include <linux/hardirq.h>
1da177e4	48
162cc279 PM	49	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	50	static struct lock_class_key rcu_lock_key;
	51	struct lockdep_map rcu_lock_map =
	52	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
	53	EXPORT_SYMBOL_GPL(rcu_lock_map);
632ee200 PM	54
	55	static struct lock_class_key rcu_bh_lock_key;
	56	struct lockdep_map rcu_bh_lock_map =
	57	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
	58	EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
	59
	60	static struct lock_class_key rcu_sched_lock_key;
	61	struct lockdep_map rcu_sched_lock_map =
	62	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
	63	EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
162cc279 PM	64	#endif
162cc279 PM	65
e3818b8d PM	66	#ifdef CONFIG_DEBUG_LOCK_ALLOC
e3818b8d PM	67
bc293d62 PM	68	int debug_lockdep_rcu_enabled(void)
	69	{
	70	return rcu_scheduler_active && debug_locks &&
	71	current->lockdep_recursion == 0;
	72	}
	73	EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
	74
e3818b8d	75	/**
ca5ecddf	76	* rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
e3818b8d PM	77	*
	78	* Check for bottom half being disabled, which covers both the
	79	* CONFIG_PROVE_RCU and not cases. Note that if someone uses
	80	* rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
ca5ecddf PM	81	* will show the situation. This is useful for debug checks in functions
	82	* that require that they be called within an RCU read-side critical
	83	* section.
e3818b8d PM	84	*
	85	* Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
	86	*/
	87	int rcu_read_lock_bh_held(void)
	88	{
	89	if (!debug_lockdep_rcu_enabled())
	90	return 1;
773e3f93	91	return in_softirq() \|\| irqs_disabled();
e3818b8d PM	92	}
	93	EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
	94
	95	#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
	96
fbf6bfca PM	97	/*
	98	* Awaken the corresponding synchronize_rcu() instance now that a
	99	* grace period has elapsed.
	100	*/
4446a36f	101	void wakeme_after_rcu(struct rcu_head *head)
21a1ea9e	102	{
01c1c660 PM	103	struct rcu_synchronize *rcu;
	104
	105	rcu = container_of(head, struct rcu_synchronize, head);
	106	complete(&rcu->completion);
21a1ea9e	107	}
ee84b824 PM	108
	109	#ifdef CONFIG_PROVE_RCU
	110	/*
	111	* wrapper function to avoid #include problems.
	112	*/
	113	int rcu_my_thread_group_empty(void)
	114	{
	115	return thread_group_empty(current);
	116	}
	117	EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
	118	#endif /* #ifdef CONFIG_PROVE_RCU */
551d55a9 MD	119
	120	#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
	121	static inline void debug_init_rcu_head(struct rcu_head *head)
	122	{
	123	debug_object_init(head, &rcuhead_debug_descr);
	124	}
	125
	126	static inline void debug_rcu_head_free(struct rcu_head *head)
	127	{
	128	debug_object_free(head, &rcuhead_debug_descr);
	129	}
	130
	131	/*
	132	* fixup_init is called when:
	133	* - an active object is initialized
	134	*/
	135	static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
	136	{
	137	struct rcu_head *head = addr;
	138
	139	switch (state) {
	140	case ODEBUG_STATE_ACTIVE:
	141	/*
	142	* Ensure that queued callbacks are all executed.
	143	* If we detect that we are nested in a RCU read-side critical
	144	* section, we should simply fail, otherwise we would deadlock.
	145	*/
	146	if (rcu_preempt_depth() != 0 \|\| preempt_count() != 0 \|\|
	147	irqs_disabled()) {
	148	WARN_ON(1);
	149	return 0;
	150	}
	151	rcu_barrier();
	152	rcu_barrier_sched();
	153	rcu_barrier_bh();
	154	debug_object_init(head, &rcuhead_debug_descr);
	155	return 1;
	156	default:
	157	return 0;
	158	}
	159	}
	160
	161	/*
	162	* fixup_activate is called when:
	163	* - an active object is activated
	164	* - an unknown object is activated (might be a statically initialized object)
	165	* Activation is performed internally by call_rcu().
	166	*/
	167	static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
	168	{
	169	struct rcu_head *head = addr;
	170
	171	switch (state) {
	172
	173	case ODEBUG_STATE_NOTAVAILABLE:
	174	/*
	175	* This is not really a fixup. We just make sure that it is
	176	* tracked in the object tracker.
	177	*/
	178	debug_object_init(head, &rcuhead_debug_descr);
	179	debug_object_activate(head, &rcuhead_debug_descr);
	180	return 0;
	181
	182	case ODEBUG_STATE_ACTIVE:
183	/*
184	* Ensure that queued callbacks are all executed.
185	* If we detect that we are nested in a RCU read-side critical
186	* section, we should simply fail, otherwise we would deadlock.
187	*/
188	if (rcu_preempt_depth() != 0 \|\| preempt_count() != 0 \|\|
189	irqs_disabled()) {
190	WARN_ON(1);
191	return 0;
192	}
193	rcu_barrier();
194	rcu_barrier_sched();
195	rcu_barrier_bh();
196	debug_object_activate(head, &rcuhead_debug_descr);
197	return 1;
198	default:
199	return 0;
200	}
201	}
202
203	/*
204	* fixup_free is called when:
205	* - an active object is freed
206	*/
207	static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
208	{
209	struct rcu_head *head = addr;
210
211	switch (state) {
212	case ODEBUG_STATE_ACTIVE:
213	/*
214	* Ensure that queued callbacks are all executed.
215	* If we detect that we are nested in a RCU read-side critical
216	* section, we should simply fail, otherwise we would deadlock.
e611eecd PM	217	* Note that the machinery to reliably determine whether
	218	* or not we are in an RCU read-side critical section
	219	* exists only in the preemptible RCU implementations
	220	* (TINY_PREEMPT_RCU and TREE_PREEMPT_RCU), which is why
	221	* DEBUG_OBJECTS_RCU_HEAD is disallowed if !PREEMPT.
551d55a9	222	*/
551d55a9 MD	223	if (rcu_preempt_depth() != 0 \|\| preempt_count() != 0 \|\|
	224	irqs_disabled()) {
	225	WARN_ON(1);
	226	return 0;
	227	}
	228	rcu_barrier();
	229	rcu_barrier_sched();
	230	rcu_barrier_bh();
	231	debug_object_free(head, &rcuhead_debug_descr);
	232	return 1;
551d55a9 MD	233	default:
	234	return 0;
	235	}
	236	}
	237
	238	/**
	239	* init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
	240	* @head: pointer to rcu_head structure to be initialized
	241	*
	242	* This function informs debugobjects of a new rcu_head structure that
	243	* has been allocated as an auto variable on the stack. This function
	244	* is not required for rcu_head structures that are statically defined or
	245	* that are dynamically allocated on the heap. This function has no
	246	* effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
	247	*/
	248	void init_rcu_head_on_stack(struct rcu_head *head)
	249	{
	250	debug_object_init_on_stack(head, &rcuhead_debug_descr);
	251	}
	252	EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
	253
	254	/**
	255	* destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
	256	* @head: pointer to rcu_head structure to be initialized
	257	*
	258	* This function informs debugobjects that an on-stack rcu_head structure
	259	* is about to go out of scope. As with init_rcu_head_on_stack(), this
	260	* function is not required for rcu_head structures that are statically
	261	* defined or that are dynamically allocated on the heap. Also as with
	262	* init_rcu_head_on_stack(), this function has no effect for
	263	* !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
	264	*/
	265	void destroy_rcu_head_on_stack(struct rcu_head *head)
	266	{
	267	debug_object_free(head, &rcuhead_debug_descr);
	268	}
	269	EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
	270
	271	struct debug_obj_descr rcuhead_debug_descr = {
	272	.name = "rcu_head",
	273	.fixup_init = rcuhead_fixup_init,
	274	.fixup_activate = rcuhead_fixup_activate,
	275	.fixup_free = rcuhead_fixup_free,
	276	};
	277	EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
	278	#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */