[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/map/urcu-bp.h"

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

#ifndef MAP_ANONYMOUS
#define MAP_ANONYMOUS MAP_ANON
#endif

#ifndef __linux__

#define MREMAP_MAYMOVE	1
#define MREMAP_FIXED	2

/*
 * mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping.
 * This is not generic.
*/
void *mremap(void *old_address, size_t old_size, size_t new_size, int flags)
{
	void *new_address;

	assert(flags & MREMAP_MAYMOVE);
	assert(!(flags & MREMAP_FIXED));
	new_address = mmap(old_address, new_size,
			   PROT_READ | PROT_WRITE,
			   MAP_ANONYMOUS | MAP_PRIVATE,
			   -1, 0);
	if (new_address == MAP_FAILED)
		return MAP_FAILED;
	if (old_address) {
		memcpy(new_address, old_address, old_size);
		munmap(old_address, old_size);
	}
	return new_address;
}
#endif

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

/*
 * Active attempts to check for reader Q.S. before calling sleep().
 */
#define RCU_QS_ACTIVE_ATTEMPTS 100

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;

	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,
		caa_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);
}

#include "urcu-call-rcu-impl.h"
#include "urcu-defer-impl.h"
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
57760d44	38	#include "urcu/map/urcu-bp.h"
5e77fc1f	39
af7c2dbe	40	#include "urcu/static/urcu-bp.h"
fdee2e6d MD	41	/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
	42	#include "urcu-bp.h"
	43
4c1ae2ea MD	44	#ifndef MAP_ANONYMOUS
	45	#define MAP_ANONYMOUS MAP_ANON
	46	#endif
	47
45a4872f MD	48	#ifndef __linux__
	49
	50	#define MREMAP_MAYMOVE 1
	51	#define MREMAP_FIXED 2
	52
	53	/*
	54	* mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping.
	55	* This is not generic.
	56	*/
	57	void mremap(void old_address, size_t old_size, size_t new_size, int flags)
	58	{
dc745ef6	59	void *new_address;
45a4872f MD	60
	61	assert(flags & MREMAP_MAYMOVE);
	62	assert(!(flags & MREMAP_FIXED));
	63	new_address = mmap(old_address, new_size,
	64	PROT_READ \| PROT_WRITE,
	65	MAP_ANONYMOUS \| MAP_PRIVATE,
	66	-1, 0);
	67	if (new_address == MAP_FAILED)
	68	return MAP_FAILED;
	69	if (old_address) {
	70	memcpy(new_address, old_address, old_size);
	71	munmap(old_address, old_size);
	72	}
	73	return new_address;
	74	}
	75	#endif
	76
fdee2e6d MD	77	/* Sleep delay in us */
	78	#define RCU_SLEEP_DELAY 1000
	79	#define ARENA_INIT_ALLOC 16
	80
b7b6a8f5 PB	81	/*
	82	* Active attempts to check for reader Q.S. before calling sleep().
	83	*/
	84	#define RCU_QS_ACTIVE_ATTEMPTS 100
	85
02be5561	86	void __attribute__((destructor)) rcu_bp_exit(void);
fdee2e6d	87
6abb4bd5	88	static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
fdee2e6d MD	89
	90	#ifdef DEBUG_YIELD
	91	unsigned int yield_active;
	92	unsigned int __thread rand_yield;
	93	#endif
	94
	95	/*
	96	* Global grace period counter.
02be5561	97	* Contains the current RCU_GP_CTR_PHASE.
fdee2e6d MD	98	* Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
	99	* Written to only by writer with mutex taken. Read by both writer and readers.
	100	*/
02be5561	101	long rcu_gp_ctr = RCU_GP_COUNT;
fdee2e6d MD	102
	103	/*
	104	* Pointer to registry elements. Written to only by each individual reader. Read
	105	* by both the reader and the writers.
	106	*/
02be5561	107	struct rcu_reader __thread *rcu_reader;
fdee2e6d	108
16aa9ee8	109	static CDS_LIST_HEAD(registry);
fdee2e6d MD	110
	111	struct registry_arena {
	112	void *p;
	113	size_t len;
	114	size_t used;
	115	};
	116
	117	static struct registry_arena registry_arena;
	118
4cf1675f MD	119	/* Saved fork signal mask, protected by rcu_gp_lock */
	120	static sigset_t saved_fork_signal_mask;
	121
fdee2e6d MD	122	static void rcu_gc_registry(void);
fdee2e6d MD	123
6abb4bd5	124	static void mutex_lock(pthread_mutex_t *mutex)
fdee2e6d MD	125	{
	126	int ret;
	127
	128	#ifndef DISTRUST_SIGNALS_EXTREME
6abb4bd5	129	ret = pthread_mutex_lock(mutex);
fdee2e6d MD	130	if (ret) {
	131	perror("Error in pthread mutex lock");
	132	exit(-1);
	133	}
	134	#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
6abb4bd5	135	while ((ret = pthread_mutex_trylock(mutex)) != 0) {
fdee2e6d MD	136	if (ret != EBUSY && ret != EINTR) {
	137	printf("ret = %d, errno = %d\n", ret, errno);
	138	perror("Error in pthread mutex lock");
	139	exit(-1);
	140	}
fdee2e6d MD	141	poll(NULL,0,10);
	142	}
	143	#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
	144	}
	145
6abb4bd5	146	static void mutex_unlock(pthread_mutex_t *mutex)
fdee2e6d MD	147	{
	148	int ret;
	149
6abb4bd5	150	ret = pthread_mutex_unlock(mutex);
fdee2e6d MD	151	if (ret) {
	152	perror("Error in pthread mutex unlock");
	153	exit(-1);
	154	}
	155	}
	156
2dfb8b5e	157	void update_counter_and_wait(void)
fdee2e6d	158	{
16aa9ee8	159	CDS_LIST_HEAD(qsreaders);
fdee2e6d	160	int wait_loops = 0;
02be5561	161	struct rcu_reader index, tmp;
fdee2e6d	162
32c15e4e	163	/* Switch parity: 0 -> 1, 1 -> 0 */
6cf3827c	164	CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
2dfb8b5e MD	165
	166	/*
	167	* Must commit qparity update to memory before waiting for other parity
	168	* quiescent state. Failure to do so could result in the writer waiting
	169	* forever while new readers are always accessing data (no progress).
6cf3827c	170	* Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED.
2dfb8b5e MD	171	*/
	172
	173	/*
5481ddb3	174	* Adding a cmm_smp_mb() which is _not_ formally required, but makes the
2dfb8b5e MD	175	* model easier to understand. It does not have a big performance impact
	176	* anyway, given this is the write-side.
	177	*/
5481ddb3	178	cmm_smp_mb();
2dfb8b5e	179
fdee2e6d	180	/*
02be5561	181	* Wait for each thread rcu_reader.ctr count to become 0.
fdee2e6d MD	182	*/
	183	for (;;) {
	184	wait_loops++;
16aa9ee8	185	cds_list_for_each_entry_safe(index, tmp, &registry, node) {
fdee2e6d	186	if (!rcu_old_gp_ongoing(&index->ctr))
16aa9ee8	187	cds_list_move(&index->node, &qsreaders);
fdee2e6d MD	188	}
fdee2e6d MD	189
16aa9ee8	190	if (cds_list_empty(&registry)) {
fdee2e6d MD	191	break;
	192	} else {
	193	if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
	194	usleep(RCU_SLEEP_DELAY);
	195	else
06f22bdb	196	caa_cpu_relax();
fdee2e6d MD	197	}
	198	}
	199	/* put back the reader list in the registry */
16aa9ee8	200	cds_list_splice(&qsreaders, &registry);
fdee2e6d MD	201	}
	202
	203	void synchronize_rcu(void)
	204	{
	205	sigset_t newmask, oldmask;
	206	int ret;
	207
	208	ret = sigemptyset(&newmask);
	209	assert(!ret);
	210	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	211	assert(!ret);
	212
6abb4bd5	213	mutex_lock(&rcu_gp_lock);
fdee2e6d	214
16aa9ee8	215	if (cds_list_empty(&registry))
2dfb8b5e	216	goto out;
fdee2e6d MD	217
fdee2e6d MD	218	/* All threads should read qparity before accessing data structure
2dfb8b5e	219	* where new ptr points to. */
fdee2e6d	220	/* Write new ptr before changing the qparity */
5481ddb3	221	cmm_smp_mb();
fdee2e6d	222
2dfb8b5e MD	223	/* Remove old registry elements */
2dfb8b5e MD	224	rcu_gc_registry();
fdee2e6d MD	225
	226	/*
	227	* Wait for previous parity to be empty of readers.
	228	*/
2dfb8b5e	229	update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */
fdee2e6d MD	230
fdee2e6d MD	231	/*
5481ddb3	232	* Adding a cmm_smp_mb() which is _not_ formally required, but makes the
fdee2e6d MD	233	* model easier to understand. It does not have a big performance impact
	234	* anyway, given this is the write-side.
	235	*/
5481ddb3	236	cmm_smp_mb();
fdee2e6d	237
fdee2e6d	238	/*
2dfb8b5e	239	* Wait for previous parity to be empty of readers.
fdee2e6d	240	*/
2dfb8b5e	241	update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */
fdee2e6d MD	242
fdee2e6d MD	243	/*
2dfb8b5e MD	244	* Finish waiting for reader threads before letting the old ptr being
2dfb8b5e MD	245	* freed.
fdee2e6d	246	*/
5481ddb3	247	cmm_smp_mb();
2dfb8b5e	248	out:
6abb4bd5	249	mutex_unlock(&rcu_gp_lock);
fdee2e6d MD	250	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	251	assert(!ret);
	252	}
	253
	254	/*
	255	* library wrappers to be used by non-LGPL compatible source code.
	256	*/
	257
	258	void rcu_read_lock(void)
	259	{
	260	_rcu_read_lock();
	261	}
	262
	263	void rcu_read_unlock(void)
	264	{
	265	_rcu_read_unlock();
	266	}
	267
	268	/*
	269	* only grow for now.
	270	*/
	271	static void resize_arena(struct registry_arena *arena, size_t len)
	272	{
	273	void *new_arena;
	274
0617bf4c MD	275	if (!arena->p)
	276	new_arena = mmap(arena->p, len,
	277	PROT_READ \| PROT_WRITE,
	278	MAP_ANONYMOUS \| MAP_PRIVATE,
	279	-1, 0);
	280	else
	281	new_arena = mremap(arena->p, arena->len,
	282	len, MREMAP_MAYMOVE);
	283	assert(new_arena != MAP_FAILED);
	284
fdee2e6d MD	285	/*
	286	* re-used the same region ?
	287	*/
	288	if (new_arena == arena->p)
	289	return;
	290
fdee2e6d MD	291	bzero(new_arena + arena->len, len - arena->len);
	292	arena->p = new_arena;
	293	}
	294
	295	/* Called with signals off and mutex locked */
	296	static void add_thread(void)
	297	{
02be5561	298	struct rcu_reader *rcu_reader_reg;
fdee2e6d MD	299
fdee2e6d MD	300	if (registry_arena.len
02be5561	301	< registry_arena.used + sizeof(struct rcu_reader))
fdee2e6d	302	resize_arena(&registry_arena,
2f8a5ae7	303	caa_max(registry_arena.len << 1, ARENA_INIT_ALLOC));
fdee2e6d MD	304	/*
	305	* Find a free spot.
	306	*/
02be5561 MD	307	for (rcu_reader_reg = registry_arena.p;
	308	(void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
	309	rcu_reader_reg++) {
	310	if (!rcu_reader_reg->alloc)
fdee2e6d MD	311	break;
fdee2e6d MD	312	}
02be5561 MD	313	rcu_reader_reg->alloc = 1;
02be5561 MD	314	registry_arena.used += sizeof(struct rcu_reader);
fdee2e6d MD	315
fdee2e6d MD	316	/* Add to registry */
02be5561 MD	317	rcu_reader_reg->tid = pthread_self();
02be5561 MD	318	assert(rcu_reader_reg->ctr == 0);
16aa9ee8	319	cds_list_add(&rcu_reader_reg->node, &registry);
02be5561	320	rcu_reader = rcu_reader_reg;
fdee2e6d MD	321	}
	322
	323	/* Called with signals off and mutex locked */
	324	static void rcu_gc_registry(void)
	325	{
02be5561	326	struct rcu_reader *rcu_reader_reg;
fdee2e6d MD	327	pthread_t tid;
	328	int ret;
	329
02be5561 MD	330	for (rcu_reader_reg = registry_arena.p;
	331	(void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
	332	rcu_reader_reg++) {
	333	if (!rcu_reader_reg->alloc)
fdee2e6d	334	continue;
02be5561	335	tid = rcu_reader_reg->tid;
fdee2e6d MD	336	ret = pthread_kill(tid, 0);
	337	assert(ret != EINVAL);
	338	if (ret == ESRCH) {
16aa9ee8	339	cds_list_del(&rcu_reader_reg->node);
79266051	340	rcu_reader_reg->ctr = 0;
02be5561 MD	341	rcu_reader_reg->alloc = 0;
02be5561 MD	342	registry_arena.used -= sizeof(struct rcu_reader);
fdee2e6d MD	343	}
	344	}
	345	}
	346
	347	/* Disable signals, take mutex, add to registry */
	348	void rcu_bp_register(void)
	349	{
	350	sigset_t newmask, oldmask;
	351	int ret;
	352
	353	ret = sigemptyset(&newmask);
	354	assert(!ret);
	355	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	356	assert(!ret);
	357
	358	/*
	359	* Check if a signal concurrently registered our thread since
	360	* the check in rcu_read_lock(). */
02be5561	361	if (rcu_reader)
fdee2e6d MD	362	goto end;
fdee2e6d MD	363
6abb4bd5	364	mutex_lock(&rcu_gp_lock);
fdee2e6d	365	add_thread();
6abb4bd5	366	mutex_unlock(&rcu_gp_lock);
fdee2e6d MD	367	end:
	368	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	369	assert(!ret);
	370	}
	371
02be5561	372	void rcu_bp_exit()
fdee2e6d MD	373	{
	374	munmap(registry_arena.p, registry_arena.len);
	375	}
4cf1675f MD	376
	377	/*
	378	* Holding the rcu_gp_lock across fork will make sure we fork() don't race with
	379	* a concurrent thread executing with this same lock held. This ensures that the
	380	* registry is in a coherent state in the child.
	381	*/
	382	void rcu_bp_before_fork(void)
	383	{
	384	sigset_t newmask, oldmask;
	385	int ret;
	386
	387	ret = sigemptyset(&newmask);
	388	assert(!ret);
	389	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	390	assert(!ret);
	391	mutex_lock(&rcu_gp_lock);
	392	saved_fork_signal_mask = oldmask;
	393	}
	394
	395	void rcu_bp_after_fork_parent(void)
	396	{
	397	sigset_t oldmask;
	398	int ret;
	399
	400	oldmask = saved_fork_signal_mask;
	401	mutex_unlock(&rcu_gp_lock);
	402	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	403	assert(!ret);
	404	}
	405
	406	void rcu_bp_after_fork_child(void)
	407	{
	408	sigset_t oldmask;
	409	int ret;
	410
	411	rcu_gc_registry();
	412	oldmask = saved_fork_signal_mask;
	413	mutex_unlock(&rcu_gp_lock);
	414	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	415	assert(!ret);
	416	}
5e77fc1f PM	417
5e77fc1f PM	418	#include "urcu-call-rcu-impl.h"
0376e7b2	419	#include "urcu-defer-impl.h"