[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 <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/export.h>
#include <linux/hardirq.h>
#include <linux/delay.h>

#define CREATE_TRACE_POINTS
#include <trace/events/rcu.h>

#include "rcu.h"

#ifdef CONFIG_PREEMPT_RCU

/*
 * Preemptible RCU implementation for rcu_read_lock().
 * Just increment ->rcu_read_lock_nesting, shared state will be updated
 * if we block.
 */
void __rcu_read_lock(void)
{
	current->rcu_read_lock_nesting++;
	barrier();  /* critical section after entry code. */
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);

/*
 * Preemptible RCU implementation for rcu_read_unlock().
 * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
 * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
 * invoke rcu_read_unlock_special() to clean up after a context switch
 * in an RCU read-side critical section and other special cases.
 */
void __rcu_read_unlock(void)
{
	struct task_struct *t = current;

	if (t->rcu_read_lock_nesting != 1) {
		--t->rcu_read_lock_nesting;
	} else {
		barrier();  /* critical section before exit code. */
		t->rcu_read_lock_nesting = INT_MIN;
#ifdef CONFIG_PROVE_RCU_DELAY
		udelay(10); /* Make preemption more probable. */
#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
		barrier();  /* assign before ->rcu_read_unlock_special load */
		if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
			rcu_read_unlock_special(t);
		barrier();  /* ->rcu_read_unlock_special load before assign */
		t->rcu_read_lock_nesting = 0;
	}
#ifdef CONFIG_PROVE_LOCKING
	{
		int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting);

		WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
	}
#endif /* #ifdef CONFIG_PROVE_LOCKING */
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);

/*
 * Check for a task exiting while in a preemptible-RCU read-side
 * critical section, clean up if so.  No need to issue warnings,
 * as debug_check_no_locks_held() already does this if lockdep
 * is enabled.
 */
void exit_rcu(void)
{
	struct task_struct *t = current;

	if (likely(list_empty(&current->rcu_node_entry)))
		return;
	t->rcu_read_lock_nesting = 1;
	barrier();
	t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
	__rcu_read_unlock();
}

#else /* #ifdef CONFIG_PREEMPT_RCU */

void exit_rcu(void)
{
}

#endif /* #else #ifdef CONFIG_PREEMPT_RCU */

#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.
 *
 * Note that rcu_read_lock() is disallowed if the CPU is either idle or
 * offline from an RCU perspective, so check for those as well.
 */
int rcu_read_lock_bh_held(void)
{
	if (!debug_lockdep_rcu_enabled())
		return 1;
	if (rcu_is_cpu_idle())
		return 0;
	if (!rcu_lockdep_current_cpu_online())
		return 0;
	return in_softirq() || irqs_disabled();
}
EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);

#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

struct rcu_synchronize {
	struct rcu_head head;
	struct completion completion;
};

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

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

void wait_rcu_gp(call_rcu_func_t crf)
{
	struct rcu_synchronize rcu;

	init_rcu_head_on_stack(&rcu.head);
	init_completion(&rcu.completion);
	/* Will wake me after RCU finished. */
	crf(&rcu.head, wakeme_after_rcu);
	/* Wait for it. */
	wait_for_completion(&rcu.completion);
	destroy_rcu_head_on_stack(&rcu.head);
}
EXPORT_SYMBOL_GPL(wait_rcu_gp);

#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.
		 * In !PREEMPT configurations, there is no way to tell if we are
		 * in a RCU read-side critical section or not, so we never
		 * attempt any fixup and just print a warning.
		 */
#ifndef CONFIG_PREEMPT
		WARN_ON_ONCE(1);
		return 0;
#endif
		if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
		    irqs_disabled()) {
			WARN_ON_ONCE(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.
		 * In !PREEMPT configurations, there is no way to tell if we are
		 * in a RCU read-side critical section or not, so we never
		 * attempt any fixup and just print a warning.
		 */
#ifndef CONFIG_PREEMPT
		WARN_ON_ONCE(1);
		return 0;
#endif
		if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
		    irqs_disabled()) {
			WARN_ON_ONCE(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.
		 * In !PREEMPT configurations, there is no way to tell if we are
		 * in a RCU read-side critical section or not, so we never
		 * attempt any fixup and just print a warning.
		 */
#ifndef CONFIG_PREEMPT
		WARN_ON_ONCE(1);
		return 0;
#endif
		if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
		    irqs_disabled()) {
			WARN_ON_ONCE(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 */

#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp)
{
	trace_rcu_torture_read(rcutorturename, rhp);
}
EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
#else
#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
#endif
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>
60063497	40	#include <linux/atomic.h>
1da177e4	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>
9984de1a	46	#include <linux/export.h>
e3818b8d	47	#include <linux/hardirq.h>
e3ebfb96	48	#include <linux/delay.h>
1da177e4	49
29c00b4a PM	50	#define CREATE_TRACE_POINTS
	51	#include <trace/events/rcu.h>
	52
	53	#include "rcu.h"
	54
9dd8fb16 PM	55	#ifdef CONFIG_PREEMPT_RCU
9dd8fb16 PM	56
2a3fa843 PM	57	/*
	58	* Preemptible RCU implementation for rcu_read_lock().
	59	* Just increment ->rcu_read_lock_nesting, shared state will be updated
	60	* if we block.
	61	*/
	62	void __rcu_read_lock(void)
	63	{
	64	current->rcu_read_lock_nesting++;
	65	barrier(); /* critical section after entry code. */
	66	}
	67	EXPORT_SYMBOL_GPL(__rcu_read_lock);
	68
	69	/*
	70	* Preemptible RCU implementation for rcu_read_unlock().
	71	* Decrement ->rcu_read_lock_nesting. If the result is zero (outermost
	72	* rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
	73	* invoke rcu_read_unlock_special() to clean up after a context switch
	74	* in an RCU read-side critical section and other special cases.
	75	*/
	76	void __rcu_read_unlock(void)
	77	{
	78	struct task_struct *t = current;
	79
	80	if (t->rcu_read_lock_nesting != 1) {
	81	--t->rcu_read_lock_nesting;
	82	} else {
	83	barrier(); /* critical section before exit code. */
	84	t->rcu_read_lock_nesting = INT_MIN;
e3ebfb96 PM	85	#ifdef CONFIG_PROVE_RCU_DELAY
	86	udelay(10); /* Make preemption more probable. */
	87	#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
2a3fa843 PM	88	barrier(); /* assign before ->rcu_read_unlock_special load */
	89	if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
	90	rcu_read_unlock_special(t);
	91	barrier(); /* ->rcu_read_unlock_special load before assign */
	92	t->rcu_read_lock_nesting = 0;
	93	}
	94	#ifdef CONFIG_PROVE_LOCKING
	95	{
	96	int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting);
	97
	98	WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
	99	}
	100	#endif /* #ifdef CONFIG_PROVE_LOCKING */
	101	}
	102	EXPORT_SYMBOL_GPL(__rcu_read_unlock);
	103
9dd8fb16 PM	104	/*
	105	* Check for a task exiting while in a preemptible-RCU read-side
	106	* critical section, clean up if so. No need to issue warnings,
	107	* as debug_check_no_locks_held() already does this if lockdep
	108	* is enabled.
	109	*/
	110	void exit_rcu(void)
	111	{
	112	struct task_struct *t = current;
	113
	114	if (likely(list_empty(&current->rcu_node_entry)))
	115	return;
	116	t->rcu_read_lock_nesting = 1;
	117	barrier();
	118	t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
	119	__rcu_read_unlock();
	120	}
	121
	122	#else /* #ifdef CONFIG_PREEMPT_RCU */
	123
	124	void exit_rcu(void)
	125	{
	126	}
	127
	128	#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
	129
162cc279 PM	130	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	131	static struct lock_class_key rcu_lock_key;
	132	struct lockdep_map rcu_lock_map =
	133	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
	134	EXPORT_SYMBOL_GPL(rcu_lock_map);
632ee200 PM	135
	136	static struct lock_class_key rcu_bh_lock_key;
	137	struct lockdep_map rcu_bh_lock_map =
	138	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
	139	EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
	140
	141	static struct lock_class_key rcu_sched_lock_key;
	142	struct lockdep_map rcu_sched_lock_map =
	143	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
	144	EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
162cc279 PM	145	#endif
162cc279 PM	146
e3818b8d PM	147	#ifdef CONFIG_DEBUG_LOCK_ALLOC
e3818b8d PM	148
bc293d62 PM	149	int debug_lockdep_rcu_enabled(void)
	150	{
	151	return rcu_scheduler_active && debug_locks &&
	152	current->lockdep_recursion == 0;
	153	}
	154	EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
	155
e3818b8d	156	/**
ca5ecddf	157	* rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
e3818b8d PM	158	*
	159	* Check for bottom half being disabled, which covers both the
	160	* CONFIG_PROVE_RCU and not cases. Note that if someone uses
	161	* rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
ca5ecddf PM	162	* will show the situation. This is useful for debug checks in functions
	163	* that require that they be called within an RCU read-side critical
	164	* section.
e3818b8d PM	165	*
e3818b8d PM	166	* Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
c0d6d01b PM	167	*
	168	* Note that rcu_read_lock() is disallowed if the CPU is either idle or
	169	* offline from an RCU perspective, so check for those as well.
e3818b8d PM	170	*/
	171	int rcu_read_lock_bh_held(void)
	172	{
	173	if (!debug_lockdep_rcu_enabled())
	174	return 1;
e6b80a3b FW	175	if (rcu_is_cpu_idle())
e6b80a3b FW	176	return 0;
c0d6d01b PM	177	if (!rcu_lockdep_current_cpu_online())
c0d6d01b PM	178	return 0;
773e3f93	179	return in_softirq() \|\| irqs_disabled();
e3818b8d PM	180	}
	181	EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
	182
	183	#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
	184
2c42818e PM	185	struct rcu_synchronize {
	186	struct rcu_head head;
	187	struct completion completion;
	188	};
	189
fbf6bfca PM	190	/*
	191	* Awaken the corresponding synchronize_rcu() instance now that a
	192	* grace period has elapsed.
	193	*/
2c42818e	194	static void wakeme_after_rcu(struct rcu_head *head)
21a1ea9e	195	{
01c1c660 PM	196	struct rcu_synchronize *rcu;
	197
	198	rcu = container_of(head, struct rcu_synchronize, head);
	199	complete(&rcu->completion);
21a1ea9e	200	}
ee84b824	201
2c42818e PM	202	void wait_rcu_gp(call_rcu_func_t crf)
	203	{
	204	struct rcu_synchronize rcu;
	205
	206	init_rcu_head_on_stack(&rcu.head);
	207	init_completion(&rcu.completion);
	208	/* Will wake me after RCU finished. */
	209	crf(&rcu.head, wakeme_after_rcu);
	210	/* Wait for it. */
	211	wait_for_completion(&rcu.completion);
	212	destroy_rcu_head_on_stack(&rcu.head);
	213	}
	214	EXPORT_SYMBOL_GPL(wait_rcu_gp);
	215
ee84b824 PM	216	#ifdef CONFIG_PROVE_RCU
	217	/*
	218	* wrapper function to avoid #include problems.
	219	*/
	220	int rcu_my_thread_group_empty(void)
	221	{
	222	return thread_group_empty(current);
	223	}
	224	EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
	225	#endif /* #ifdef CONFIG_PROVE_RCU */
551d55a9 MD	226
	227	#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
	228	static inline void debug_init_rcu_head(struct rcu_head *head)
	229	{
	230	debug_object_init(head, &rcuhead_debug_descr);
	231	}
	232
	233	static inline void debug_rcu_head_free(struct rcu_head *head)
	234	{
	235	debug_object_free(head, &rcuhead_debug_descr);
	236	}
	237
	238	/*
	239	* fixup_init is called when:
	240	* - an active object is initialized
	241	*/
	242	static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
	243	{
	244	struct rcu_head *head = addr;
	245
	246	switch (state) {
	247	case ODEBUG_STATE_ACTIVE:
	248	/*
	249	* Ensure that queued callbacks are all executed.
	250	* If we detect that we are nested in a RCU read-side critical
	251	* section, we should simply fail, otherwise we would deadlock.
fc2ecf7e MD	252	* In !PREEMPT configurations, there is no way to tell if we are
	253	* in a RCU read-side critical section or not, so we never
	254	* attempt any fixup and just print a warning.
551d55a9	255	*/
fc2ecf7e	256	#ifndef CONFIG_PREEMPT
108aae22	257	WARN_ON_ONCE(1);
fc2ecf7e MD	258	return 0;
fc2ecf7e MD	259	#endif
551d55a9 MD	260	if (rcu_preempt_depth() != 0 \|\| preempt_count() != 0 \|\|
551d55a9 MD	261	irqs_disabled()) {
108aae22	262	WARN_ON_ONCE(1);
551d55a9 MD	263	return 0;
	264	}
	265	rcu_barrier();
	266	rcu_barrier_sched();
	267	rcu_barrier_bh();
	268	debug_object_init(head, &rcuhead_debug_descr);
	269	return 1;
	270	default:
	271	return 0;
	272	}
	273	}
	274
	275	/*
	276	* fixup_activate is called when:
	277	* - an active object is activated
	278	* - an unknown object is activated (might be a statically initialized object)
	279	* Activation is performed internally by call_rcu().
	280	*/
	281	static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
	282	{
	283	struct rcu_head *head = addr;
	284
	285	switch (state) {
	286
	287	case ODEBUG_STATE_NOTAVAILABLE:
	288	/*
	289	* This is not really a fixup. We just make sure that it is
	290	* tracked in the object tracker.
	291	*/
	292	debug_object_init(head, &rcuhead_debug_descr);
	293	debug_object_activate(head, &rcuhead_debug_descr);
	294	return 0;
	295
	296	case ODEBUG_STATE_ACTIVE:
	297	/*
	298	* Ensure that queued callbacks are all executed.
	299	* If we detect that we are nested in a RCU read-side critical
	300	* section, we should simply fail, otherwise we would deadlock.
fc2ecf7e MD	301	* In !PREEMPT configurations, there is no way to tell if we are
	302	* in a RCU read-side critical section or not, so we never
	303	* attempt any fixup and just print a warning.
551d55a9	304	*/
fc2ecf7e	305	#ifndef CONFIG_PREEMPT
108aae22	306	WARN_ON_ONCE(1);
fc2ecf7e MD	307	return 0;
fc2ecf7e MD	308	#endif
551d55a9 MD	309	if (rcu_preempt_depth() != 0 \|\| preempt_count() != 0 \|\|
551d55a9 MD	310	irqs_disabled()) {
108aae22	311	WARN_ON_ONCE(1);
551d55a9 MD	312	return 0;
	313	}
	314	rcu_barrier();
	315	rcu_barrier_sched();
	316	rcu_barrier_bh();
	317	debug_object_activate(head, &rcuhead_debug_descr);
	318	return 1;
	319	default:
	320	return 0;
	321	}
	322	}
	323
	324	/*
	325	* fixup_free is called when:
	326	* - an active object is freed
	327	*/
	328	static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
	329	{
	330	struct rcu_head *head = addr;
	331
	332	switch (state) {
	333	case ODEBUG_STATE_ACTIVE:
	334	/*
	335	* Ensure that queued callbacks are all executed.
	336	* If we detect that we are nested in a RCU read-side critical
	337	* section, we should simply fail, otherwise we would deadlock.
fc2ecf7e MD	338	* In !PREEMPT configurations, there is no way to tell if we are
	339	* in a RCU read-side critical section or not, so we never
	340	* attempt any fixup and just print a warning.
551d55a9	341	*/
fc2ecf7e	342	#ifndef CONFIG_PREEMPT
108aae22	343	WARN_ON_ONCE(1);
fc2ecf7e MD	344	return 0;
fc2ecf7e MD	345	#endif
551d55a9 MD	346	if (rcu_preempt_depth() != 0 \|\| preempt_count() != 0 \|\|
551d55a9 MD	347	irqs_disabled()) {
108aae22	348	WARN_ON_ONCE(1);
551d55a9 MD	349	return 0;
	350	}
	351	rcu_barrier();
	352	rcu_barrier_sched();
	353	rcu_barrier_bh();
	354	debug_object_free(head, &rcuhead_debug_descr);
	355	return 1;
551d55a9 MD	356	default:
	357	return 0;
	358	}
	359	}
	360
	361	/**
	362	* init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
	363	* @head: pointer to rcu_head structure to be initialized
	364	*
	365	* This function informs debugobjects of a new rcu_head structure that
	366	* has been allocated as an auto variable on the stack. This function
	367	* is not required for rcu_head structures that are statically defined or
	368	* that are dynamically allocated on the heap. This function has no
	369	* effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
	370	*/
	371	void init_rcu_head_on_stack(struct rcu_head *head)
	372	{
	373	debug_object_init_on_stack(head, &rcuhead_debug_descr);
	374	}
	375	EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
	376
	377	/**
	378	* destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
	379	* @head: pointer to rcu_head structure to be initialized
	380	*
	381	* This function informs debugobjects that an on-stack rcu_head structure
	382	* is about to go out of scope. As with init_rcu_head_on_stack(), this
	383	* function is not required for rcu_head structures that are statically
	384	* defined or that are dynamically allocated on the heap. Also as with
	385	* init_rcu_head_on_stack(), this function has no effect for
	386	* !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
	387	*/
	388	void destroy_rcu_head_on_stack(struct rcu_head *head)
	389	{
	390	debug_object_free(head, &rcuhead_debug_descr);
	391	}
	392	EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
	393
	394	struct debug_obj_descr rcuhead_debug_descr = {
	395	.name = "rcu_head",
	396	.fixup_init = rcuhead_fixup_init,
	397	.fixup_activate = rcuhead_fixup_activate,
	398	.fixup_free = rcuhead_fixup_free,
	399	};
	400	EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
	401	#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
91afaf30 PM	402
	403	#if defined(CONFIG_TREE_RCU) \|\| defined(CONFIG_TREE_PREEMPT_RCU) \|\| defined(CONFIG_RCU_TRACE)
	404	void do_trace_rcu_torture_read(char rcutorturename, struct rcu_head rhp)
	405	{
	406	trace_rcu_torture_read(rcutorturename, rhp);
	407	}
	408	EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
	409	#else
	410	#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
	411	#endif