[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
#define _LGPL_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/wfqueue.h"
#include "urcu/map/urcu-bp.h"
#include "urcu/static/urcu-bp.h"
#include "urcu-pointer.h"
#include "urcu/tls-compat.h"

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

#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;
DEFINE_URCU_TLS(unsigned int, 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.
 */
DEFINE_URCU_TLS(struct rcu_reader *, 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);
	URCU_TLS(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 (URCU_TLS(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(void)
{
	if (registry_arena.p)
		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);
}

void *rcu_dereference_sym_bp(void *p)
{
	return _rcu_dereference(p);
}

void *rcu_set_pointer_sym_bp(void **p, void *v)
{
	cmm_wmb();
	return uatomic_set(p, v);
}

void *rcu_xchg_pointer_sym_bp(void **p, void *v)
{
	cmm_wmb();
	return uatomic_xchg(p, v);
}

void *rcu_cmpxchg_pointer_sym_bp(void **p, void *old, void *_new)
{
	cmm_wmb();
	return uatomic_cmpxchg(p, old, _new);
}

DEFINE_RCU_FLAVOR(rcu_flavor);

#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
71c811bf	27	#define _LGPL_SOURCE
fdee2e6d MD	28	#include <stdio.h>
	29	#include <pthread.h>
	30	#include <signal.h>
	31	#include <assert.h>
	32	#include <stdlib.h>
	33	#include <string.h>
	34	#include <errno.h>
	35	#include <poll.h>
	36	#include <unistd.h>
	37	#include <sys/mman.h>
	38
71c811bf	39	#include "urcu/wfqueue.h"
57760d44	40	#include "urcu/map/urcu-bp.h"
af7c2dbe	41	#include "urcu/static/urcu-bp.h"
618b2595	42	#include "urcu-pointer.h"
bd252a04	43	#include "urcu/tls-compat.h"
71c811bf	44
fdee2e6d	45	/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
71c811bf	46	#undef _LGPL_SOURCE
fdee2e6d	47	#include "urcu-bp.h"
71c811bf	48	#define _LGPL_SOURCE
fdee2e6d	49
4c1ae2ea MD	50	#ifndef MAP_ANONYMOUS
	51	#define MAP_ANONYMOUS MAP_ANON
	52	#endif
	53
45a4872f MD	54	#ifndef __linux__
	55
	56	#define MREMAP_MAYMOVE 1
	57	#define MREMAP_FIXED 2
	58
	59	/*
	60	* mremap wrapper for non-Linux systems. Maps a RW, anonymous private mapping.
	61	* This is not generic.
	62	*/
	63	void mremap(void old_address, size_t old_size, size_t new_size, int flags)
	64	{
dc745ef6	65	void *new_address;
45a4872f MD	66
	67	assert(flags & MREMAP_MAYMOVE);
	68	assert(!(flags & MREMAP_FIXED));
	69	new_address = mmap(old_address, new_size,
	70	PROT_READ \| PROT_WRITE,
	71	MAP_ANONYMOUS \| MAP_PRIVATE,
	72	-1, 0);
	73	if (new_address == MAP_FAILED)
	74	return MAP_FAILED;
	75	if (old_address) {
	76	memcpy(new_address, old_address, old_size);
	77	munmap(old_address, old_size);
	78	}
	79	return new_address;
	80	}
	81	#endif
	82
fdee2e6d MD	83	/* Sleep delay in us */
	84	#define RCU_SLEEP_DELAY 1000
	85	#define ARENA_INIT_ALLOC 16
	86
b7b6a8f5 PB	87	/*
	88	* Active attempts to check for reader Q.S. before calling sleep().
	89	*/
	90	#define RCU_QS_ACTIVE_ATTEMPTS 100
	91
02be5561	92	void __attribute__((destructor)) rcu_bp_exit(void);
fdee2e6d	93
6abb4bd5	94	static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
fdee2e6d MD	95
	96	#ifdef DEBUG_YIELD
	97	unsigned int yield_active;
bd252a04	98	DEFINE_URCU_TLS(unsigned int, rand_yield);
fdee2e6d MD	99	#endif
	100
	101	/*
	102	* Global grace period counter.
02be5561	103	* Contains the current RCU_GP_CTR_PHASE.
fdee2e6d MD	104	* Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
	105	* Written to only by writer with mutex taken. Read by both writer and readers.
	106	*/
02be5561	107	long rcu_gp_ctr = RCU_GP_COUNT;
fdee2e6d MD	108
	109	/*
	110	* Pointer to registry elements. Written to only by each individual reader. Read
	111	* by both the reader and the writers.
	112	*/
bd252a04	113	DEFINE_URCU_TLS(struct rcu_reader *, rcu_reader);
fdee2e6d	114
16aa9ee8	115	static CDS_LIST_HEAD(registry);
fdee2e6d MD	116
	117	struct registry_arena {
	118	void *p;
	119	size_t len;
	120	size_t used;
	121	};
	122
	123	static struct registry_arena registry_arena;
	124
4cf1675f MD	125	/* Saved fork signal mask, protected by rcu_gp_lock */
	126	static sigset_t saved_fork_signal_mask;
	127
fdee2e6d MD	128	static void rcu_gc_registry(void);
fdee2e6d MD	129
6abb4bd5	130	static void mutex_lock(pthread_mutex_t *mutex)
fdee2e6d MD	131	{
	132	int ret;
	133
	134	#ifndef DISTRUST_SIGNALS_EXTREME
6abb4bd5	135	ret = pthread_mutex_lock(mutex);
fdee2e6d MD	136	if (ret) {
	137	perror("Error in pthread mutex lock");
	138	exit(-1);
	139	}
	140	#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
6abb4bd5	141	while ((ret = pthread_mutex_trylock(mutex)) != 0) {
fdee2e6d MD	142	if (ret != EBUSY && ret != EINTR) {
	143	printf("ret = %d, errno = %d\n", ret, errno);
	144	perror("Error in pthread mutex lock");
	145	exit(-1);
	146	}
fdee2e6d MD	147	poll(NULL,0,10);
	148	}
	149	#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
	150	}
	151
6abb4bd5	152	static void mutex_unlock(pthread_mutex_t *mutex)
fdee2e6d MD	153	{
	154	int ret;
	155
6abb4bd5	156	ret = pthread_mutex_unlock(mutex);
fdee2e6d MD	157	if (ret) {
	158	perror("Error in pthread mutex unlock");
	159	exit(-1);
	160	}
	161	}
	162
2dfb8b5e	163	void update_counter_and_wait(void)
fdee2e6d	164	{
16aa9ee8	165	CDS_LIST_HEAD(qsreaders);
fdee2e6d	166	int wait_loops = 0;
02be5561	167	struct rcu_reader index, tmp;
fdee2e6d	168
32c15e4e	169	/* Switch parity: 0 -> 1, 1 -> 0 */
6cf3827c	170	CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
2dfb8b5e MD	171
	172	/*
	173	* Must commit qparity update to memory before waiting for other parity
	174	* quiescent state. Failure to do so could result in the writer waiting
	175	* forever while new readers are always accessing data (no progress).
6cf3827c	176	* Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED.
2dfb8b5e MD	177	*/
	178
	179	/*
5481ddb3	180	* Adding a cmm_smp_mb() which is _not_ formally required, but makes the
2dfb8b5e MD	181	* model easier to understand. It does not have a big performance impact
	182	* anyway, given this is the write-side.
	183	*/
5481ddb3	184	cmm_smp_mb();
2dfb8b5e	185
fdee2e6d	186	/*
02be5561	187	* Wait for each thread rcu_reader.ctr count to become 0.
fdee2e6d MD	188	*/
	189	for (;;) {
	190	wait_loops++;
16aa9ee8	191	cds_list_for_each_entry_safe(index, tmp, &registry, node) {
fdee2e6d	192	if (!rcu_old_gp_ongoing(&index->ctr))
16aa9ee8	193	cds_list_move(&index->node, &qsreaders);
fdee2e6d MD	194	}
fdee2e6d MD	195
16aa9ee8	196	if (cds_list_empty(&registry)) {
fdee2e6d MD	197	break;
	198	} else {
	199	if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
	200	usleep(RCU_SLEEP_DELAY);
	201	else
06f22bdb	202	caa_cpu_relax();
fdee2e6d MD	203	}
	204	}
	205	/* put back the reader list in the registry */
16aa9ee8	206	cds_list_splice(&qsreaders, &registry);
fdee2e6d MD	207	}
	208
	209	void synchronize_rcu(void)
	210	{
	211	sigset_t newmask, oldmask;
	212	int ret;
	213
	214	ret = sigemptyset(&newmask);
	215	assert(!ret);
	216	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	217	assert(!ret);
	218
6abb4bd5	219	mutex_lock(&rcu_gp_lock);
fdee2e6d	220
16aa9ee8	221	if (cds_list_empty(&registry))
2dfb8b5e	222	goto out;
fdee2e6d MD	223
fdee2e6d MD	224	/* All threads should read qparity before accessing data structure
2dfb8b5e	225	* where new ptr points to. */
fdee2e6d	226	/* Write new ptr before changing the qparity */
5481ddb3	227	cmm_smp_mb();
fdee2e6d	228
2dfb8b5e MD	229	/* Remove old registry elements */
2dfb8b5e MD	230	rcu_gc_registry();
fdee2e6d MD	231
	232	/*
	233	* Wait for previous parity to be empty of readers.
	234	*/
2dfb8b5e	235	update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */
fdee2e6d MD	236
fdee2e6d MD	237	/*
5481ddb3	238	* Adding a cmm_smp_mb() which is _not_ formally required, but makes the
fdee2e6d MD	239	* model easier to understand. It does not have a big performance impact
	240	* anyway, given this is the write-side.
	241	*/
5481ddb3	242	cmm_smp_mb();
fdee2e6d	243
fdee2e6d	244	/*
2dfb8b5e	245	* Wait for previous parity to be empty of readers.
fdee2e6d	246	*/
2dfb8b5e	247	update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */
fdee2e6d MD	248
fdee2e6d MD	249	/*
2dfb8b5e MD	250	* Finish waiting for reader threads before letting the old ptr being
2dfb8b5e MD	251	* freed.
fdee2e6d	252	*/
5481ddb3	253	cmm_smp_mb();
2dfb8b5e	254	out:
6abb4bd5	255	mutex_unlock(&rcu_gp_lock);
fdee2e6d MD	256	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	257	assert(!ret);
	258	}
	259
	260	/*
	261	* library wrappers to be used by non-LGPL compatible source code.
	262	*/
	263
	264	void rcu_read_lock(void)
	265	{
	266	_rcu_read_lock();
	267	}
	268
	269	void rcu_read_unlock(void)
	270	{
	271	_rcu_read_unlock();
	272	}
	273
	274	/*
	275	* only grow for now.
	276	*/
	277	static void resize_arena(struct registry_arena *arena, size_t len)
	278	{
	279	void *new_arena;
	280
0617bf4c MD	281	if (!arena->p)
	282	new_arena = mmap(arena->p, len,
	283	PROT_READ \| PROT_WRITE,
	284	MAP_ANONYMOUS \| MAP_PRIVATE,
	285	-1, 0);
	286	else
	287	new_arena = mremap(arena->p, arena->len,
	288	len, MREMAP_MAYMOVE);
	289	assert(new_arena != MAP_FAILED);
	290
fdee2e6d MD	291	/*
	292	* re-used the same region ?
	293	*/
	294	if (new_arena == arena->p)
	295	return;
	296
fdee2e6d MD	297	bzero(new_arena + arena->len, len - arena->len);
	298	arena->p = new_arena;
	299	}
	300
	301	/* Called with signals off and mutex locked */
	302	static void add_thread(void)
	303	{
02be5561	304	struct rcu_reader *rcu_reader_reg;
fdee2e6d MD	305
fdee2e6d MD	306	if (registry_arena.len
02be5561	307	< registry_arena.used + sizeof(struct rcu_reader))
fdee2e6d	308	resize_arena(&registry_arena,
2f8a5ae7	309	caa_max(registry_arena.len << 1, ARENA_INIT_ALLOC));
fdee2e6d MD	310	/*
	311	* Find a free spot.
	312	*/
02be5561 MD	313	for (rcu_reader_reg = registry_arena.p;
	314	(void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
	315	rcu_reader_reg++) {
	316	if (!rcu_reader_reg->alloc)
fdee2e6d MD	317	break;
fdee2e6d MD	318	}
02be5561 MD	319	rcu_reader_reg->alloc = 1;
02be5561 MD	320	registry_arena.used += sizeof(struct rcu_reader);
fdee2e6d MD	321
fdee2e6d MD	322	/* Add to registry */
02be5561 MD	323	rcu_reader_reg->tid = pthread_self();
02be5561 MD	324	assert(rcu_reader_reg->ctr == 0);
16aa9ee8	325	cds_list_add(&rcu_reader_reg->node, &registry);
bd252a04	326	URCU_TLS(rcu_reader) = rcu_reader_reg;
fdee2e6d MD	327	}
	328
	329	/* Called with signals off and mutex locked */
	330	static void rcu_gc_registry(void)
	331	{
02be5561	332	struct rcu_reader *rcu_reader_reg;
fdee2e6d MD	333	pthread_t tid;
	334	int ret;
	335
02be5561 MD	336	for (rcu_reader_reg = registry_arena.p;
	337	(void *)rcu_reader_reg < registry_arena.p + registry_arena.len;
	338	rcu_reader_reg++) {
	339	if (!rcu_reader_reg->alloc)
fdee2e6d	340	continue;
02be5561	341	tid = rcu_reader_reg->tid;
fdee2e6d MD	342	ret = pthread_kill(tid, 0);
	343	assert(ret != EINVAL);
	344	if (ret == ESRCH) {
16aa9ee8	345	cds_list_del(&rcu_reader_reg->node);
79266051	346	rcu_reader_reg->ctr = 0;
02be5561 MD	347	rcu_reader_reg->alloc = 0;
02be5561 MD	348	registry_arena.used -= sizeof(struct rcu_reader);
fdee2e6d MD	349	}
	350	}
	351	}
	352
	353	/* Disable signals, take mutex, add to registry */
	354	void rcu_bp_register(void)
	355	{
	356	sigset_t newmask, oldmask;
	357	int ret;
	358
	359	ret = sigemptyset(&newmask);
	360	assert(!ret);
	361	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	362	assert(!ret);
	363
	364	/*
	365	* Check if a signal concurrently registered our thread since
	366	* the check in rcu_read_lock(). */
bd252a04	367	if (URCU_TLS(rcu_reader))
fdee2e6d MD	368	goto end;
fdee2e6d MD	369
6abb4bd5	370	mutex_lock(&rcu_gp_lock);
fdee2e6d	371	add_thread();
6abb4bd5	372	mutex_unlock(&rcu_gp_lock);
fdee2e6d MD	373	end:
	374	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	375	assert(!ret);
	376	}
	377
9380711a	378	void rcu_bp_exit(void)
fdee2e6d	379	{
9380711a MD	380	if (registry_arena.p)
9380711a MD	381	munmap(registry_arena.p, registry_arena.len);
fdee2e6d	382	}
4cf1675f MD	383
	384	/*
	385	* Holding the rcu_gp_lock across fork will make sure we fork() don't race with
	386	* a concurrent thread executing with this same lock held. This ensures that the
	387	* registry is in a coherent state in the child.
	388	*/
	389	void rcu_bp_before_fork(void)
	390	{
	391	sigset_t newmask, oldmask;
	392	int ret;
	393
	394	ret = sigemptyset(&newmask);
	395	assert(!ret);
	396	ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
	397	assert(!ret);
	398	mutex_lock(&rcu_gp_lock);
	399	saved_fork_signal_mask = oldmask;
	400	}
	401
	402	void rcu_bp_after_fork_parent(void)
	403	{
	404	sigset_t oldmask;
	405	int ret;
	406
	407	oldmask = saved_fork_signal_mask;
	408	mutex_unlock(&rcu_gp_lock);
	409	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	410	assert(!ret);
	411	}
	412
	413	void rcu_bp_after_fork_child(void)
	414	{
	415	sigset_t oldmask;
	416	int ret;
	417
	418	rcu_gc_registry();
	419	oldmask = saved_fork_signal_mask;
	420	mutex_unlock(&rcu_gp_lock);
	421	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
	422	assert(!ret);
	423	}
5e77fc1f	424
9b7981bb MD	425	void rcu_dereference_sym_bp(void p)
	426	{
	427	return _rcu_dereference(p);
	428	}
	429
5efd3cd2 MD	430	void rcu_set_pointer_sym_bp(void p, void v)
	431	{
	432	cmm_wmb();
	433	return uatomic_set(p, v);
	434	}
	435
	436	void rcu_xchg_pointer_sym_bp(void p, void v)
	437	{
	438	cmm_wmb();
	439	return uatomic_xchg(p, v);
	440	}
	441
	442	void rcu_cmpxchg_pointer_sym_bp(void p, void old, void *_new)
	443	{
	444	cmm_wmb();
	445	return uatomic_cmpxchg(p, old, _new);
	446	}
	447
5e6b23a6	448	DEFINE_RCU_FLAVOR(rcu_flavor);
541d828d	449
5e77fc1f	450	#include "urcu-call-rcu-impl.h"
0376e7b2	451	#include "urcu-defer-impl.h"