[urcu.git] / urcu-bp.c

/*
 * urcu-bp.c
 *
 * Userspace RCU library, "bulletproof" version.
 *
 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
 */

#define _GNU_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <signal.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <poll.h>
#include <unistd.h>
#include <sys/mman.h>

#include "urcu-bp-static.h"
/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
#include "urcu-bp.h"

/* Sleep delay in us */
#define RCU_SLEEP_DELAY		1000
#define ARENA_INIT_ALLOC	16

void __attribute__((destructor)) rcu_bp_exit(void);

static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;

#ifdef DEBUG_YIELD
unsigned int yield_active;
unsigned int __thread rand_yield;
#endif

/*
 * Global grace period counter.
 * Contains the current RCU_GP_CTR_PHASE.
 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
 * Written to only by writer with mutex taken. Read by both writer and readers.
 */
long rcu_gp_ctr = RCU_GP_COUNT;

/*
 * Pointer to registry elements. Written to only by each individual reader. Read
 * by both the reader and the writers.
 */
struct rcu_reader __thread *rcu_reader;

static CDS_LIST_HEAD(registry);

struct registry_arena {
	void *p;
	size_t len;
	size_t used;
};

static struct registry_arena registry_arena;

/* Saved fork signal mask, protected by rcu_gp_lock */
static sigset_t saved_fork_signal_mask;

static void rcu_gc_registry(void);

static void mutex_lock(pthread_mutex_t *mutex)
{
	int ret;

#ifndef DISTRUST_SIGNALS_EXTREME
	ret = pthread_mutex_lock(mutex);
	if (ret) {
		perror("Error in pthread mutex lock");
		exit(-1);
	}
#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
	while ((ret = pthread_mutex_trylock(mutex)) != 0) {
		if (ret != EBUSY && ret != EINTR) {
			printf("ret = %d, errno = %d\n", ret, errno);
			perror("Error in pthread mutex lock");
			exit(-1);
		}
		poll(NULL,0,10);
	}
#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
}

static void mutex_unlock(pthread_mutex_t *mutex)
{
	int ret;

	ret = pthread_mutex_unlock(mutex);
	if (ret) {
		perror("Error in pthread mutex unlock");
		exit(-1);
	}
}

void update_counter_and_wait(void)
{
	CDS_LIST_HEAD(qsreaders);
	int wait_loops = 0;
	struct rcu_reader *index, *tmp;

	/* Switch parity: 0 -> 1, 1 -> 0 */
	CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);

	/*
	 * Must commit qparity update to memory before waiting for other parity
	 * quiescent state. Failure to do so could result in the writer waiting
	 * forever while new readers are always accessing data (no progress).
	 * Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED.
	 */

	/*
	 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
	 * model easier to understand. It does not have a big performance impact
	 * anyway, given this is the write-side.
	 */
	cmm_smp_mb();

	/*
	 * Wait for each thread rcu_reader.ctr count to become 0.
	 */
	for (;;) {
		wait_loops++;
		cds_list_for_each_entry_safe(index, tmp, &registry, node) {
			if (!rcu_old_gp_ongoing(&index->ctr))
				cds_list_move(&index->node, &qsreaders);
		}

		if (cds_list_empty(&registry)) {
			break;
		} else {
			if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
				usleep(RCU_SLEEP_DELAY);
			else
				caa_cpu_relax();
		}
	}
	/* put back the reader list in the registry */
	cds_list_splice(&qsreaders, &registry);
}

void synchronize_rcu(void)
{
	sigset_t newmask, oldmask;
	int ret;

	ret = sigemptyset(&newmask);
	assert(!ret);
	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	assert(!ret);

	mutex_lock(&rcu_gp_lock);

	if (cds_list_empty(&registry))
		goto out;

	/* All threads should read qparity before accessing data structure
	 * where new ptr points to. */
	/* Write new ptr before changing the qparity */
	cmm_smp_mb();

	/* Remove old registry elements */
	rcu_gc_registry();

	/*
	 * Wait for previous parity to be empty of readers.
	 */
	update_counter_and_wait();	/* 0 -> 1, wait readers in parity 0 */

	/*
	 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
	 * model easier to understand. It does not have a big performance impact
	 * anyway, given this is the write-side.
	 */
	cmm_smp_mb();

	/*
	 * Wait for previous parity to be empty of readers.
	 */
	update_counter_and_wait();	/* 1 -> 0, wait readers in parity 1 */

	/*
	 * Finish waiting for reader threads before letting the old ptr being
	 * freed.
	 */
	cmm_smp_mb();
out:
	mutex_unlock(&rcu_gp_lock);
	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	assert(!ret);
}

/*
 * library wrappers to be used by non-LGPL compatible source code.
 */

void rcu_read_lock(void)
{
	_rcu_read_lock();
}

void rcu_read_unlock(void)
{
	_rcu_read_unlock();
}

/*
 * only grow for now.
 */
static void resize_arena(struct registry_arena *arena, size_t len)
{
	void *new_arena;

	if (!arena->p)
		new_arena = mmap(arena->p, len,
				 PROT_READ | PROT_WRITE,
				 MAP_ANONYMOUS | MAP_PRIVATE,
				 -1, 0);
	else
		new_arena = mremap(arena->p, arena->len,
				   len, MREMAP_MAYMOVE);
	assert(new_arena != MAP_FAILED);

	/*
	 * re-used the same region ?
	 */
	if (new_arena == arena->p)
		return;

	memcpy(new_arena, arena->p, arena->len);
	bzero(new_arena + arena->len, len - arena->len);
	arena->p = new_arena;
}

/* Called with signals off and mutex locked */
static void add_thread(void)
{
	struct rcu_reader *rcu_reader_reg;

	if (registry_arena.len
	    < registry_arena.used + sizeof(struct rcu_reader))
		resize_arena(&registry_arena,
		max(registry_arena.len << 1, ARENA_INIT_ALLOC));
	/*
	 * Find a free spot.
	 */
	for (rcu_reader_reg = registry_arena.p;
	     (void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
	     rcu_reader_reg++) {
		if (!rcu_reader_reg->alloc)
			break;
	}
	rcu_reader_reg->alloc = 1;
	registry_arena.used += sizeof(struct rcu_reader);

	/* Add to registry */
	rcu_reader_reg->tid = pthread_self();
	assert(rcu_reader_reg->ctr == 0);
	cds_list_add(&rcu_reader_reg->node, &registry);
	rcu_reader = rcu_reader_reg;
}

/* Called with signals off and mutex locked */
static void rcu_gc_registry(void)
{
	struct rcu_reader *rcu_reader_reg;
	pthread_t tid;
	int ret;

	for (rcu_reader_reg = registry_arena.p;
	     (void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
	     rcu_reader_reg++) {
		if (!rcu_reader_reg->alloc)
			continue;
		tid = rcu_reader_reg->tid;
		ret = pthread_kill(tid, 0);
		assert(ret != EINVAL);
		if (ret == ESRCH) {
			cds_list_del(&rcu_reader_reg->node);
			rcu_reader_reg->ctr = 0;
			rcu_reader_reg->alloc = 0;
			registry_arena.used -= sizeof(struct rcu_reader);
		}
	}
}

/* Disable signals, take mutex, add to registry */
void rcu_bp_register(void)
{
	sigset_t newmask, oldmask;
	int ret;

	ret = sigemptyset(&newmask);
	assert(!ret);
	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	assert(!ret);

	/*
	 * Check if a signal concurrently registered our thread since
	 * the check in rcu_read_lock(). */
	if (rcu_reader)
		goto end;

	mutex_lock(&rcu_gp_lock);
	add_thread();
	mutex_unlock(&rcu_gp_lock);
end:
	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	assert(!ret);
}

void rcu_bp_exit()
{
	munmap(registry_arena.p, registry_arena.len);
}

/*
 * Holding the rcu_gp_lock across fork will make sure we fork() don't race with
 * a concurrent thread executing with this same lock held. This ensures that the
 * registry is in a coherent state in the child.
 */
void rcu_bp_before_fork(void)
{
	sigset_t newmask, oldmask;
	int ret;

	ret = sigemptyset(&newmask);
	assert(!ret);
	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	assert(!ret);
	mutex_lock(&rcu_gp_lock);
	saved_fork_signal_mask = oldmask;
}

void rcu_bp_after_fork_parent(void)
{
	sigset_t oldmask;
	int ret;

	oldmask = saved_fork_signal_mask;
	mutex_unlock(&rcu_gp_lock);
	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	assert(!ret);
}

void rcu_bp_after_fork_child(void)
{
	sigset_t oldmask;
	int ret;

	rcu_gc_registry();
	oldmask = saved_fork_signal_mask;
	mutex_unlock(&rcu_gp_lock);
	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	assert(!ret);
}
Commit	Line	Data
fdee2e6d MD	1	/*
	2	* urcu-bp.c
	3	*
	4	* Userspace RCU library, "bulletproof" version.
	5	*
6982d6d7	6	* Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
fdee2e6d MD	7	* Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
	8	*
	9	* This library is free software; you can redistribute it and/or
	10	* modify it under the terms of the GNU Lesser General Public
	11	* License as published by the Free Software Foundation; either
	12	* version 2.1 of the License, or (at your option) any later version.
	13	*
	14	* This library is distributed in the hope that it will be useful,
	15	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	16	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	17	* Lesser General Public License for more details.
	18	*
	19	* You should have received a copy of the GNU Lesser General Public
	20	* License along with this library; if not, write to the Free Software
	21	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	22	*
	23	* IBM's contributions to this file may be relicensed under LGPLv2 or later.
	24	*/
	25
0617bf4c	26	#define _GNU_SOURCE
fdee2e6d MD	27	#include <stdio.h>
	28	#include <pthread.h>
	29	#include <signal.h>
	30	#include <assert.h>
	31	#include <stdlib.h>
	32	#include <string.h>
	33	#include <errno.h>
	34	#include <poll.h>
	35	#include <unistd.h>
	36	#include <sys/mman.h>
	37
	38	#include "urcu-bp-static.h"
	39	/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
	40	#include "urcu-bp.h"
	41
	42	/* Sleep delay in us */
	43	#define RCU_SLEEP_DELAY 1000
	44	#define ARENA_INIT_ALLOC 16
	45
02be5561	46	void __attribute__((destructor)) rcu_bp_exit(void);
fdee2e6d	47
6abb4bd5	48	static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
fdee2e6d MD	49
	50	#ifdef DEBUG_YIELD
	51	unsigned int yield_active;
	52	unsigned int __thread rand_yield;
	53	#endif
	54
	55	/*
	56	* Global grace period counter.
02be5561	57	* Contains the current RCU_GP_CTR_PHASE.
fdee2e6d MD	58	* Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
	59	* Written to only by writer with mutex taken. Read by both writer and readers.
	60	*/
02be5561	61	long rcu_gp_ctr = RCU_GP_COUNT;
fdee2e6d MD	62
	63	/*
	64	* Pointer to registry elements. Written to only by each individual reader. Read
	65	* by both the reader and the writers.
	66	*/
02be5561	67	struct rcu_reader __thread *rcu_reader;
fdee2e6d	68
16aa9ee8	69	static CDS_LIST_HEAD(registry);
fdee2e6d MD	70
	71	struct registry_arena {
	72	void *p;
	73	size_t len;
	74	size_t used;
	75	};
	76
	77	static struct registry_arena registry_arena;
	78
4cf1675f MD	79	/* Saved fork signal mask, protected by rcu_gp_lock */
	80	static sigset_t saved_fork_signal_mask;
	81
fdee2e6d MD	82	static void rcu_gc_registry(void);
fdee2e6d MD	83
6abb4bd5	84	static void mutex_lock(pthread_mutex_t *mutex)
fdee2e6d MD	85	{
	86	int ret;
	87
	88	#ifndef DISTRUST_SIGNALS_EXTREME
6abb4bd5	89	ret = pthread_mutex_lock(mutex);
fdee2e6d MD	90	if (ret) {
	91	perror("Error in pthread mutex lock");
	92	exit(-1);
	93	}
	94	#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
6abb4bd5	95	while ((ret = pthread_mutex_trylock(mutex)) != 0) {
fdee2e6d MD	96	if (ret != EBUSY && ret != EINTR) {
	97	printf("ret = %d, errno = %d\n", ret, errno);
	98	perror("Error in pthread mutex lock");
	99	exit(-1);
	100	}
fdee2e6d MD	101	poll(NULL,0,10);
	102	}
	103	#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
	104	}
	105
6abb4bd5	106	static void mutex_unlock(pthread_mutex_t *mutex)
fdee2e6d MD	107	{
	108	int ret;
	109
6abb4bd5	110	ret = pthread_mutex_unlock(mutex);
fdee2e6d MD	111	if (ret) {
	112	perror("Error in pthread mutex unlock");
	113	exit(-1);
	114	}
	115	}
	116
2dfb8b5e	117	void update_counter_and_wait(void)
fdee2e6d	118	{
16aa9ee8	119	CDS_LIST_HEAD(qsreaders);
fdee2e6d	120	int wait_loops = 0;
02be5561	121	struct rcu_reader index, tmp;
fdee2e6d	122
32c15e4e	123	/* Switch parity: 0 -> 1, 1 -> 0 */
6cf3827c	124	CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
2dfb8b5e MD	125
	126	/*
	127	* Must commit qparity update to memory before waiting for other parity
	128	* quiescent state. Failure to do so could result in the writer waiting
	129	* forever while new readers are always accessing data (no progress).
6cf3827c	130	* Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED.
2dfb8b5e MD	131	*/
	132
	133	/*
5481ddb3	134	* Adding a cmm_smp_mb() which is _not_ formally required, but makes the
2dfb8b5e MD	135	* model easier to understand. It does not have a big performance impact
	136	* anyway, given this is the write-side.
	137	*/
5481ddb3	138	cmm_smp_mb();
2dfb8b5e	139
fdee2e6d	140	/*
02be5561	141	* Wait for each thread rcu_reader.ctr count to become 0.
fdee2e6d MD	142	*/
	143	for (;;) {
	144	wait_loops++;
16aa9ee8	145	cds_list_for_each_entry_safe(index, tmp, &registry, node) {
fdee2e6d	146	if (!rcu_old_gp_ongoing(&index->ctr))
16aa9ee8	147	cds_list_move(&index->node, &qsreaders);
fdee2e6d MD	148	}
fdee2e6d MD	149
16aa9ee8	150	if (cds_list_empty(&registry)) {
fdee2e6d MD	151	break;
	152	} else {
	153	if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
	154	usleep(RCU_SLEEP_DELAY);
	155	else
06f22bdb	156	caa_cpu_relax();
fdee2e6d MD	157	}
	158	}
	159	/* put back the reader list in the registry */
16aa9ee8	160	cds_list_splice(&qsreaders, &registry);
fdee2e6d MD	161	}
	162
	163	void synchronize_rcu(void)
	164	{
	165	sigset_t newmask, oldmask;
	166	int ret;
	167
	168	ret = sigemptyset(&newmask);
	169	assert(!ret);
	170	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	171	assert(!ret);
	172
6abb4bd5	173	mutex_lock(&rcu_gp_lock);
fdee2e6d	174
16aa9ee8	175	if (cds_list_empty(&registry))
2dfb8b5e	176	goto out;
fdee2e6d MD	177
fdee2e6d MD	178	/* All threads should read qparity before accessing data structure
2dfb8b5e	179	* where new ptr points to. */
fdee2e6d	180	/* Write new ptr before changing the qparity */
5481ddb3	181	cmm_smp_mb();
fdee2e6d	182
2dfb8b5e MD	183	/* Remove old registry elements */
2dfb8b5e MD	184	rcu_gc_registry();
fdee2e6d MD	185
	186	/*
	187	* Wait for previous parity to be empty of readers.
	188	*/
2dfb8b5e	189	update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */
fdee2e6d MD	190
fdee2e6d MD	191	/*
5481ddb3	192	* Adding a cmm_smp_mb() which is _not_ formally required, but makes the
fdee2e6d MD	193	* model easier to understand. It does not have a big performance impact
	194	* anyway, given this is the write-side.
	195	*/
5481ddb3	196	cmm_smp_mb();
fdee2e6d	197
fdee2e6d	198	/*
2dfb8b5e	199	* Wait for previous parity to be empty of readers.
fdee2e6d	200	*/
2dfb8b5e	201	update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */
fdee2e6d MD	202
fdee2e6d MD	203	/*
2dfb8b5e MD	204	* Finish waiting for reader threads before letting the old ptr being
2dfb8b5e MD	205	* freed.
fdee2e6d	206	*/
5481ddb3	207	cmm_smp_mb();
2dfb8b5e	208	out:
6abb4bd5	209	mutex_unlock(&rcu_gp_lock);
fdee2e6d MD	210	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	211	assert(!ret);
	212	}
	213
	214	/*
	215	* library wrappers to be used by non-LGPL compatible source code.
	216	*/
	217
	218	void rcu_read_lock(void)
	219	{
	220	_rcu_read_lock();
	221	}
	222
	223	void rcu_read_unlock(void)
	224	{
	225	_rcu_read_unlock();
	226	}
	227
	228	/*
	229	* only grow for now.
	230	*/
	231	static void resize_arena(struct registry_arena *arena, size_t len)
	232	{
	233	void *new_arena;
	234
0617bf4c MD	235	if (!arena->p)
	236	new_arena = mmap(arena->p, len,
	237	PROT_READ \| PROT_WRITE,
	238	MAP_ANONYMOUS \| MAP_PRIVATE,
	239	-1, 0);
	240	else
	241	new_arena = mremap(arena->p, arena->len,
	242	len, MREMAP_MAYMOVE);
	243	assert(new_arena != MAP_FAILED);
	244
fdee2e6d MD	245	/*
	246	* re-used the same region ?
	247	*/
	248	if (new_arena == arena->p)
	249	return;
	250
	251	memcpy(new_arena, arena->p, arena->len);
	252	bzero(new_arena + arena->len, len - arena->len);
	253	arena->p = new_arena;
	254	}
	255
	256	/* Called with signals off and mutex locked */
	257	static void add_thread(void)
	258	{
02be5561	259	struct rcu_reader *rcu_reader_reg;
fdee2e6d MD	260
fdee2e6d MD	261	if (registry_arena.len
02be5561	262	< registry_arena.used + sizeof(struct rcu_reader))
fdee2e6d MD	263	resize_arena(&registry_arena,
	264	max(registry_arena.len << 1, ARENA_INIT_ALLOC));
	265	/*
	266	* Find a free spot.
	267	*/
02be5561 MD	268	for (rcu_reader_reg = registry_arena.p;
	269	(void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
	270	rcu_reader_reg++) {
	271	if (!rcu_reader_reg->alloc)
fdee2e6d MD	272	break;
fdee2e6d MD	273	}
02be5561 MD	274	rcu_reader_reg->alloc = 1;
02be5561 MD	275	registry_arena.used += sizeof(struct rcu_reader);
fdee2e6d MD	276
fdee2e6d MD	277	/* Add to registry */
02be5561 MD	278	rcu_reader_reg->tid = pthread_self();
02be5561 MD	279	assert(rcu_reader_reg->ctr == 0);
16aa9ee8	280	cds_list_add(&rcu_reader_reg->node, &registry);
02be5561	281	rcu_reader = rcu_reader_reg;
fdee2e6d MD	282	}
	283
	284	/* Called with signals off and mutex locked */
	285	static void rcu_gc_registry(void)
	286	{
02be5561	287	struct rcu_reader *rcu_reader_reg;
fdee2e6d MD	288	pthread_t tid;
	289	int ret;
	290
02be5561 MD	291	for (rcu_reader_reg = registry_arena.p;
	292	(void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
	293	rcu_reader_reg++) {
	294	if (!rcu_reader_reg->alloc)
fdee2e6d	295	continue;
02be5561	296	tid = rcu_reader_reg->tid;
fdee2e6d MD	297	ret = pthread_kill(tid, 0);
	298	assert(ret != EINVAL);
	299	if (ret == ESRCH) {
16aa9ee8	300	cds_list_del(&rcu_reader_reg->node);
79266051	301	rcu_reader_reg->ctr = 0;
02be5561 MD	302	rcu_reader_reg->alloc = 0;
02be5561 MD	303	registry_arena.used -= sizeof(struct rcu_reader);
fdee2e6d MD	304	}
	305	}
	306	}
	307
	308	/* Disable signals, take mutex, add to registry */
	309	void rcu_bp_register(void)
	310	{
	311	sigset_t newmask, oldmask;
	312	int ret;
	313
	314	ret = sigemptyset(&newmask);
	315	assert(!ret);
	316	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	317	assert(!ret);
	318
	319	/*
	320	* Check if a signal concurrently registered our thread since
	321	* the check in rcu_read_lock(). */
02be5561	322	if (rcu_reader)
fdee2e6d MD	323	goto end;
fdee2e6d MD	324
6abb4bd5	325	mutex_lock(&rcu_gp_lock);
fdee2e6d	326	add_thread();
6abb4bd5	327	mutex_unlock(&rcu_gp_lock);
fdee2e6d MD	328	end:
	329	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	330	assert(!ret);
	331	}
	332
02be5561	333	void rcu_bp_exit()
fdee2e6d MD	334	{
	335	munmap(registry_arena.p, registry_arena.len);
	336	}
4cf1675f MD	337
	338	/*
	339	* Holding the rcu_gp_lock across fork will make sure we fork() don't race with
	340	* a concurrent thread executing with this same lock held. This ensures that the
	341	* registry is in a coherent state in the child.
	342	*/
	343	void rcu_bp_before_fork(void)
	344	{
	345	sigset_t newmask, oldmask;
	346	int ret;
	347
	348	ret = sigemptyset(&newmask);
	349	assert(!ret);
	350	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	351	assert(!ret);
	352	mutex_lock(&rcu_gp_lock);
	353	saved_fork_signal_mask = oldmask;
	354	}
	355
	356	void rcu_bp_after_fork_parent(void)
	357	{
	358	sigset_t oldmask;
	359	int ret;
	360
	361	oldmask = saved_fork_signal_mask;
	362	mutex_unlock(&rcu_gp_lock);
	363	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	364	assert(!ret);
	365	}
	366
	367	void rcu_bp_after_fork_child(void)
	368	{
	369	sigset_t oldmask;
	370	int ret;
	371
	372	rcu_gc_registry();
	373	oldmask = saved_fork_signal_mask;
	374	mutex_unlock(&rcu_gp_lock);
	375	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	376	assert(!ret);
	377	}