*
* Userspace RCU library
*
- * Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
*
- * Distributed under GPLv2
+ * 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 _BSD_SOURCE
+#define _GNU_SOURCE
+#define _LGPL_SOURCE
+#define _DEFAULT_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <signal.h>
#include <assert.h>
#include <stdlib.h>
+#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <poll.h>
+#include "urcu/wfcqueue.h"
+#include "urcu/map/urcu.h"
+#include "urcu/static/urcu.h"
+#include "urcu-pointer.h"
+#include "urcu/tls-compat.h"
+
+#include "urcu-die.h"
+#include "urcu-wait.h"
+
+/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
+#undef _LGPL_SOURCE
#include "urcu.h"
+#define _LGPL_SOURCE
-pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
+/*
+ * If a reader is really non-cooperative and refuses to commit its
+ * rcu_active_readers count to memory (there is no barrier in the reader
+ * per-se), kick it after 10 loops waiting for it.
+ */
+#define KICK_READER_LOOPS 10
/*
- * Global grace period counter.
- * Contains the current RCU_GP_CTR_BIT.
- * Also has a RCU_GP_CTR_BIT of 1, to accelerate the reader fast path.
- * Written to only by writer with mutex taken. Read by both writer and readers.
+ * Active attempts to check for reader Q.S. before calling futex().
*/
-long urcu_gp_ctr = RCU_GP_COUNT;
+#define RCU_QS_ACTIVE_ATTEMPTS 100
/*
- * Written to only by each individual reader. Read by both the reader and the
- * writers.
+ * RCU_MEMBARRIER is only possibly available on Linux.
*/
-long __thread urcu_active_readers;
+#if defined(RCU_MEMBARRIER) && defined(__linux__)
+#include <urcu/syscall-compat.h>
+#endif
+
+/* If the headers do not support SYS_membarrier, fall back on RCU_MB */
+#ifdef SYS_membarrier
+# define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__)
+#else
+# define membarrier(...) -ENOSYS
+#endif
+
+#define MEMBARRIER_EXPEDITED (1 << 0)
+#define MEMBARRIER_DELAYED (1 << 1)
+#define MEMBARRIER_QUERY (1 << 16)
+
+#ifdef RCU_MEMBARRIER
+static int init_done;
+int rcu_has_sys_membarrier;
+
+void __attribute__((constructor)) rcu_init(void);
+#endif
-/* Thread IDs of registered readers */
-#define INIT_NUM_THREADS 4
+#ifdef RCU_MB
+void rcu_init(void)
+{
+}
+#endif
-struct reader_registry {
- pthread_t tid;
- long *urcu_active_readers;
- char *need_mb;
-};
+#ifdef RCU_SIGNAL
+static int init_done;
-#ifdef DEBUG_YIELD
-unsigned int yield_active;
-unsigned int __thread rand_yield;
+void __attribute__((constructor)) rcu_init(void);
+void __attribute__((destructor)) rcu_exit(void);
#endif
-static struct reader_registry *registry;
-static char __thread need_mb;
-static int num_readers, alloc_readers;
+/*
+ * rcu_gp_lock ensures mutual exclusion between threads calling
+ * synchronize_rcu().
+ */
+static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
+/*
+ * rcu_registry_lock ensures mutual exclusion between threads
+ * registering and unregistering themselves to/from the registry, and
+ * with threads reading that registry from synchronize_rcu(). However,
+ * this lock is not held all the way through the completion of awaiting
+ * for the grace period. It is sporadically released between iterations
+ * on the registry.
+ * rcu_registry_lock may nest inside rcu_gp_lock.
+ */
+static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER;
+struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
+
+/*
+ * 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);
+
+/*
+ * Queue keeping threads awaiting to wait for a grace period. Contains
+ * struct gp_waiters_thread objects.
+ */
+static DEFINE_URCU_WAIT_QUEUE(gp_waiters);
-void internal_urcu_lock(void)
+static void mutex_lock(pthread_mutex_t *mutex)
{
int ret;
#ifndef DISTRUST_SIGNALS_EXTREME
- ret = pthread_mutex_lock(&urcu_mutex);
- if (ret) {
- perror("Error in pthread mutex lock");
- exit(-1);
- }
+ ret = pthread_mutex_lock(mutex);
+ if (ret)
+ urcu_die(ret);
#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
- while ((ret = pthread_mutex_trylock(&urcu_mutex)) != 0) {
- if (ret != EBUSY && ret != EINTR) {
- printf("ret = %d, errno = %d\n", ret, errno);
- perror("Error in pthread mutex lock");
- exit(-1);
- }
- if (need_mb) {
- smp_mb();
- need_mb = 0;
- smp_mb();
+ while ((ret = pthread_mutex_trylock(mutex)) != 0) {
+ if (ret != EBUSY && ret != EINTR)
+ urcu_die(ret);
+ if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) {
+ cmm_smp_mb();
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
+ cmm_smp_mb();
}
- poll(NULL,0,10);
+ (void) poll(NULL, 0, 10);
}
#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
}
-void internal_urcu_unlock(void)
+static void mutex_unlock(pthread_mutex_t *mutex)
{
int ret;
- ret = pthread_mutex_unlock(&urcu_mutex);
- if (ret) {
- perror("Error in pthread mutex unlock");
- exit(-1);
- }
+ ret = pthread_mutex_unlock(mutex);
+ if (ret)
+ urcu_die(ret);
}
-/*
- * called with urcu_mutex held.
- */
-static void switch_next_urcu_qparity(void)
+#ifdef RCU_MEMBARRIER
+static void smp_mb_master(int group)
{
- STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT);
+ if (caa_likely(rcu_has_sys_membarrier))
+ (void) membarrier(MEMBARRIER_EXPEDITED);
+ else
+ cmm_smp_mb();
}
+#endif
-#ifdef DEBUG_FULL_MB
-#ifdef HAS_INCOHERENT_CACHES
-static void force_mb_single_thread(struct reader_registry *index)
+#ifdef RCU_MB
+static void smp_mb_master(int group)
{
- smp_mb();
+ cmm_smp_mb();
}
-#endif /* #ifdef HAS_INCOHERENT_CACHES */
+#endif
-static void force_mb_all_threads(void)
+#ifdef RCU_SIGNAL
+static void force_mb_all_readers(void)
{
- smp_mb();
-}
-#else /* #ifdef DEBUG_FULL_MB */
-#ifdef HAS_INCOHERENT_CACHES
-static void force_mb_single_thread(struct reader_registry *index)
-{
- assert(registry);
- /*
- * pthread_kill has a smp_mb(). But beware, we assume it performs
- * a cache flush on architectures with non-coherent cache. Let's play
- * safe and don't assume anything : we use smp_mc() to make sure the
- * cache flush is enforced.
- */
- *index->need_mb = 1;
- smp_mc(); /* write ->need_mb before sending the signals */
- pthread_kill(index->tid, SIGURCU);
- smp_mb();
- /*
- * Wait for sighandler (and thus mb()) to execute on every thread.
- * BUSY-LOOP.
- */
- while (*index->need_mb) {
- poll(NULL, 0, 1);
- }
- smp_mb(); /* read ->need_mb before ending the barrier */
-}
-#endif /* #ifdef HAS_INCOHERENT_CACHES */
+ struct rcu_reader *index;
-static void force_mb_all_threads(void)
-{
- struct reader_registry *index;
/*
- * Ask for each threads to execute a smp_mb() so we can consider the
+ * Ask for each threads to execute a cmm_smp_mb() so we can consider the
* compiler barriers around rcu read lock as real memory barriers.
*/
- if (!registry)
+ if (cds_list_empty(®istry))
return;
/*
- * pthread_kill has a smp_mb(). But beware, we assume it performs
+ * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs
* a cache flush on architectures with non-coherent cache. Let's play
- * safe and don't assume anything : we use smp_mc() to make sure the
+ * safe and don't assume anything : we use cmm_smp_mc() to make sure the
* cache flush is enforced.
*/
- for (index = registry; index < registry + num_readers; index++) {
- *index->need_mb = 1;
- smp_mc(); /* write need_mb before sending the signal */
- pthread_kill(index->tid, SIGURCU);
+ cds_list_for_each_entry(index, ®istry, node) {
+ CMM_STORE_SHARED(index->need_mb, 1);
+ pthread_kill(index->tid, SIGRCU);
}
/*
* Wait for sighandler (and thus mb()) to execute on every thread.
* relevant bug report. For Linux kernels, we recommend getting
* the Linux Test Project (LTP).
*/
- for (index = registry; index < registry + num_readers; index++) {
- while (*index->need_mb) {
- pthread_kill(index->tid, SIGURCU);
- poll(NULL, 0, 1);
+ cds_list_for_each_entry(index, ®istry, node) {
+ while (CMM_LOAD_SHARED(index->need_mb)) {
+ pthread_kill(index->tid, SIGRCU);
+ (void) poll(NULL, 0, 1);
}
}
- smp_mb(); /* read ->need_mb before ending the barrier */
+ cmm_smp_mb(); /* read ->need_mb before ending the barrier */
}
-#endif /* #else #ifdef DEBUG_FULL_MB */
-void wait_for_quiescent_state(void)
+static void smp_mb_master(int group)
{
- struct reader_registry *index;
+ force_mb_all_readers();
+}
+#endif /* #ifdef RCU_SIGNAL */
+
+/*
+ * synchronize_rcu() waiting. Single thread.
+ */
+static void wait_gp(void)
+{
+ /* Read reader_gp before read futex */
+ smp_mb_master(RCU_MB_GROUP);
+ if (uatomic_read(&rcu_gp.futex) == -1)
+ futex_async(&rcu_gp.futex, FUTEX_WAIT, -1,
+ NULL, NULL, 0);
+}
+
+/*
+ * Always called with rcu_registry lock held. Releases this lock between
+ * iterations and grabs it again. Holds the lock when it returns.
+ */
+static void wait_for_readers(struct cds_list_head *input_readers,
+ struct cds_list_head *cur_snap_readers,
+ struct cds_list_head *qsreaders)
+{
+ unsigned int wait_loops = 0;
+ struct rcu_reader *index, *tmp;
+#ifdef HAS_INCOHERENT_CACHES
+ unsigned int wait_gp_loops = 0;
+#endif /* HAS_INCOHERENT_CACHES */
- if (!registry)
- return;
/*
- * Wait for each thread urcu_active_readers count to become 0.
+ * Wait for each thread URCU_TLS(rcu_reader).ctr to either
+ * indicate quiescence (not nested), or observe the current
+ * rcu_gp.ctr value.
*/
- for (index = registry; index < registry + num_readers; index++) {
+ for (;;) {
+ if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS)
+ wait_loops++;
+ if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
+ uatomic_dec(&rcu_gp.futex);
+ /* Write futex before read reader_gp */
+ smp_mb_master(RCU_MB_GROUP);
+ }
+
+ cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
+ switch (rcu_reader_state(&index->ctr)) {
+ case RCU_READER_ACTIVE_CURRENT:
+ if (cur_snap_readers) {
+ cds_list_move(&index->node,
+ cur_snap_readers);
+ break;
+ }
+ /* Fall-through */
+ case RCU_READER_INACTIVE:
+ cds_list_move(&index->node, qsreaders);
+ break;
+ case RCU_READER_ACTIVE_OLD:
+ /*
+ * Old snapshot. Leaving node in
+ * input_readers will make us busy-loop
+ * until the snapshot becomes current or
+ * the reader becomes inactive.
+ */
+ break;
+ }
+ }
+
#ifndef HAS_INCOHERENT_CACHES
- while (rcu_old_gp_ongoing(index->urcu_active_readers))
- cpu_relax();
+ if (cds_list_empty(input_readers)) {
+ if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
+ /* Read reader_gp before write futex */
+ smp_mb_master(RCU_MB_GROUP);
+ uatomic_set(&rcu_gp.futex, 0);
+ }
+ break;
+ } else {
+ /* Temporarily unlock the registry lock. */
+ mutex_unlock(&rcu_registry_lock);
+ if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS)
+ wait_gp();
+ else
+ caa_cpu_relax();
+ /* Re-lock the registry lock before the next loop. */
+ mutex_lock(&rcu_registry_lock);
+ }
#else /* #ifndef HAS_INCOHERENT_CACHES */
- int wait_loops = 0;
/*
* BUSY-LOOP. Force the reader thread to commit its
- * urcu_active_readers update to memory if we wait for too long.
+ * URCU_TLS(rcu_reader).ctr update to memory if we wait
+ * for too long.
*/
- while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
- if (wait_loops++ == KICK_READER_LOOPS) {
- force_mb_single_thread(index);
- wait_loops = 0;
+ if (cds_list_empty(input_readers)) {
+ if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
+ /* Read reader_gp before write futex */
+ smp_mb_master(RCU_MB_GROUP);
+ uatomic_set(&rcu_gp.futex, 0);
+ }
+ break;
+ } else {
+ if (wait_gp_loops == KICK_READER_LOOPS) {
+ smp_mb_master(RCU_MB_GROUP);
+ wait_gp_loops = 0;
+ }
+ /* Temporarily unlock the registry lock. */
+ mutex_unlock(&rcu_registry_lock);
+ if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
+ wait_gp();
+ wait_gp_loops++;
} else {
- cpu_relax();
+ caa_cpu_relax();
}
+ /* Re-lock the registry lock before the next loop. */
+ mutex_lock(&rcu_registry_lock);
}
#endif /* #else #ifndef HAS_INCOHERENT_CACHES */
}
void synchronize_rcu(void)
{
- internal_urcu_lock();
+ CDS_LIST_HEAD(cur_snap_readers);
+ CDS_LIST_HEAD(qsreaders);
+ DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
+ struct urcu_waiters waiters;
+
+ /*
+ * Add ourself to gp_waiters queue of threads awaiting to wait
+ * for a grace period. Proceed to perform the grace period only
+ * if we are the first thread added into the queue.
+ * The implicit memory barrier before urcu_wait_add()
+ * orders prior memory accesses of threads put into the wait
+ * queue before their insertion into the wait queue.
+ */
+ if (urcu_wait_add(&gp_waiters, &wait) != 0) {
+ /* Not first in queue: will be awakened by another thread. */
+ urcu_adaptative_busy_wait(&wait);
+ /* Order following memory accesses after grace period. */
+ cmm_smp_mb();
+ return;
+ }
+ /* We won't need to wake ourself up */
+ urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
- /* All threads should read qparity before accessing data structure
- * where new ptr points to. Must be done within internal_urcu_lock
- * because it iterates on reader threads.*/
+ mutex_lock(&rcu_gp_lock);
+
+ /*
+ * Move all waiters into our local queue.
+ */
+ urcu_move_waiters(&waiters, &gp_waiters);
+
+ mutex_lock(&rcu_registry_lock);
+
+ if (cds_list_empty(®istry))
+ goto out;
+
+ /*
+ * All threads should read qparity before accessing data structure
+ * where new ptr points to. Must be done within rcu_registry_lock
+ * because it iterates on reader threads.
+ */
/* Write new ptr before changing the qparity */
- force_mb_all_threads();
+ smp_mb_master(RCU_MB_GROUP);
- switch_next_urcu_qparity(); /* 0 -> 1 */
+ /*
+ * Wait for readers to observe original parity or be quiescent.
+ * wait_for_readers() can release and grab again rcu_registry_lock
+ * interally.
+ */
+ wait_for_readers(®istry, &cur_snap_readers, &qsreaders);
/*
- * Must commit qparity update to memory before waiting for parity
- * 0 quiescent state. Failure to do so could result in the writer
- * waiting forever while new readers are always accessing data (no
- * progress).
- * Ensured by STORE_SHARED and LOAD_SHARED.
+ * Must finish waiting for quiescent state for original parity before
+ * committing next rcu_gp.ctr update to memory. Failure to do so could
+ * result in the writer waiting forever while new readers are always
+ * accessing data (no progress). Enforce compiler-order of load
+ * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr.
*/
+ cmm_barrier();
/*
- * Wait for previous parity to be empty of readers.
+ * 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.
*/
- wait_for_quiescent_state(); /* Wait readers in parity 0 */
+ cmm_smp_mb();
+
+ /* Switch parity: 0 -> 1, 1 -> 0 */
+ CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE);
/*
- * Must finish waiting for quiescent state for parity 0 before
- * committing qparity update to memory. Failure to do so could result in
- * the writer waiting forever while new readers are always accessing
- * data (no progress).
- * Ensured by STORE_SHARED and LOAD_SHARED.
+ * Must commit rcu_gp.ctr update to memory before waiting for quiescent
+ * state. Failure to do so could result in the writer waiting forever
+ * while new readers are always accessing data (no progress). Enforce
+ * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr.
*/
+ cmm_barrier();
- switch_next_urcu_qparity(); /* 1 -> 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();
/*
- * Must commit qparity update to memory before waiting for parity
- * 1 quiescent state. Failure to do so could result in the writer
- * waiting forever while new readers are always accessing data (no
- * progress).
- * Ensured by STORE_SHARED and LOAD_SHARED.
+ * Wait for readers to observe new parity or be quiescent.
+ * wait_for_readers() can release and grab again rcu_registry_lock
+ * interally.
*/
+ wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
/*
- * Wait for previous parity to be empty of readers.
+ * Put quiescent reader list back into registry.
*/
- wait_for_quiescent_state(); /* Wait readers in parity 1 */
+ cds_list_splice(&qsreaders, ®istry);
- /* Finish waiting for reader threads before letting the old ptr being
- * freed. Must be done within internal_urcu_lock because it iterates on
- * reader threads. */
- force_mb_all_threads();
+ /*
+ * Finish waiting for reader threads before letting the old ptr
+ * being freed. Must be done within rcu_registry_lock because it
+ * iterates on reader threads.
+ */
+ smp_mb_master(RCU_MB_GROUP);
+out:
+ mutex_unlock(&rcu_registry_lock);
+ mutex_unlock(&rcu_gp_lock);
- internal_urcu_unlock();
+ /*
+ * Wakeup waiters only after we have completed the grace period
+ * and have ensured the memory barriers at the end of the grace
+ * period have been issued.
+ */
+ urcu_wake_all_waiters(&waiters);
}
-void urcu_add_reader(pthread_t id)
+/*
+ * library wrappers to be used by non-LGPL compatible source code.
+ */
+
+void rcu_read_lock(void)
{
- struct reader_registry *oldarray;
+ _rcu_read_lock();
+}
- if (!registry) {
- alloc_readers = INIT_NUM_THREADS;
- num_readers = 0;
- registry =
- malloc(sizeof(struct reader_registry) * alloc_readers);
- }
- if (alloc_readers < num_readers + 1) {
- oldarray = registry;
- registry = malloc(sizeof(struct reader_registry)
- * (alloc_readers << 1));
- memcpy(registry, oldarray,
- sizeof(struct reader_registry) * alloc_readers);
- alloc_readers <<= 1;
- free(oldarray);
- }
- registry[num_readers].tid = id;
- /* reference to the TLS of _this_ reader thread. */
- registry[num_readers].urcu_active_readers = &urcu_active_readers;
- registry[num_readers].need_mb = &need_mb;
- num_readers++;
+void rcu_read_unlock(void)
+{
+ _rcu_read_unlock();
}
-/*
- * Never shrink (implementation limitation).
- * This is O(nb threads). Eventually use a hash table.
- */
-void urcu_remove_reader(pthread_t id)
+int rcu_read_ongoing(void)
{
- struct reader_registry *index;
-
- assert(registry != NULL);
- for (index = registry; index < registry + num_readers; index++) {
- if (pthread_equal(index->tid, id)) {
- memcpy(index, ®istry[num_readers - 1],
- sizeof(struct reader_registry));
- registry[num_readers - 1].tid = 0;
- registry[num_readers - 1].urcu_active_readers = NULL;
- num_readers--;
- return;
- }
- }
- /* Hrm not found, forgot to register ? */
- assert(0);
+ return _rcu_read_ongoing();
}
-void urcu_register_thread(void)
+void rcu_register_thread(void)
{
- internal_urcu_lock();
- urcu_add_reader(pthread_self());
- internal_urcu_unlock();
+ URCU_TLS(rcu_reader).tid = pthread_self();
+ assert(URCU_TLS(rcu_reader).need_mb == 0);
+ assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK));
+
+ mutex_lock(&rcu_registry_lock);
+ rcu_init(); /* In case gcc does not support constructor attribute */
+ cds_list_add(&URCU_TLS(rcu_reader).node, ®istry);
+ mutex_unlock(&rcu_registry_lock);
}
-void urcu_unregister_thread(void)
+void rcu_unregister_thread(void)
{
- internal_urcu_lock();
- urcu_remove_reader(pthread_self());
- internal_urcu_unlock();
+ mutex_lock(&rcu_registry_lock);
+ cds_list_del(&URCU_TLS(rcu_reader).node);
+ mutex_unlock(&rcu_registry_lock);
}
-#ifndef DEBUG_FULL_MB
-void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
+#ifdef RCU_MEMBARRIER
+void rcu_init(void)
+{
+ if (init_done)
+ return;
+ init_done = 1;
+ if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
+ rcu_has_sys_membarrier = 1;
+}
+#endif
+
+#ifdef RCU_SIGNAL
+static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
{
/*
- * Executing this smp_mb() is the only purpose of this signal handler.
- * It punctually promotes barrier() into smp_mb() on every thread it is
+ * Executing this cmm_smp_mb() is the only purpose of this signal handler.
+ * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is
* executed on.
*/
- smp_mb();
- need_mb = 0;
- smp_mb();
+ cmm_smp_mb();
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
+ cmm_smp_mb();
}
-void __attribute__((constructor)) urcu_init(void)
+/*
+ * rcu_init constructor. Called when the library is linked, but also when
+ * reader threads are calling rcu_register_thread().
+ * Should only be called by a single thread at a given time. This is ensured by
+ * holing the rcu_registry_lock from rcu_register_thread() or by running
+ * at library load time, which should not be executed by multiple
+ * threads nor concurrently with rcu_register_thread() anyway.
+ */
+void rcu_init(void)
{
struct sigaction act;
int ret;
- act.sa_sigaction = sigurcu_handler;
- ret = sigaction(SIGURCU, &act, NULL);
- if (ret) {
- perror("Error in sigaction");
- exit(-1);
- }
+ if (init_done)
+ return;
+ init_done = 1;
+
+ act.sa_sigaction = sigrcu_handler;
+ act.sa_flags = SA_SIGINFO | SA_RESTART;
+ sigemptyset(&act.sa_mask);
+ ret = sigaction(SIGRCU, &act, NULL);
+ if (ret)
+ urcu_die(errno);
}
-void __attribute__((destructor)) urcu_exit(void)
+void rcu_exit(void)
{
- struct sigaction act;
- int ret;
-
- ret = sigaction(SIGURCU, NULL, &act);
- if (ret) {
- perror("Error in sigaction");
- exit(-1);
- }
- assert(act.sa_sigaction == sigurcu_handler);
- free(registry);
+ /*
+ * Don't unregister the SIGRCU signal handler anymore, because
+ * call_rcu threads could still be using it shortly before the
+ * application exits.
+ * Assertion disabled because call_rcu threads are now rcu
+ * readers, and left running at exit.
+ * assert(cds_list_empty(®istry));
+ */
}
-#endif /* #ifndef DEBUG_FULL_MB */
+
+#endif /* #ifdef RCU_SIGNAL */
+
+DEFINE_RCU_FLAVOR(rcu_flavor);
+
+#include "urcu-call-rcu-impl.h"
+#include "urcu-defer-impl.h"
projects / urcu.git / blobdiff