X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=8fd6195662d33a996467fe78a065cacf7d739b01;hp=475b4d1c991a00832409ae7332e6317442b1f042;hb=5e13fab888d07ba3657ac9e1eb0441450ea17837;hpb=0a52082baa5dd26455966c42a96f3185767590b7 diff --git a/urcu.c b/urcu.c index 475b4d1..8fd6195 100644 --- a/urcu.c +++ b/urcu.c @@ -3,9 +3,24 @@ * * Userspace RCU library * - * Copyright February 2009 - Mathieu Desnoyers + * Copyright (c) 2009 Mathieu Desnoyers + * 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. */ #include @@ -14,7 +29,11 @@ #include #include #include +#include +#include +#include "urcu-static.h" +/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ #include "urcu.h" pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER; @@ -39,6 +58,7 @@ long __thread urcu_active_readers; struct reader_registry { pthread_t tid; long *urcu_active_readers; + char *need_mb; }; #ifdef DEBUG_YIELD @@ -47,24 +67,34 @@ unsigned int __thread rand_yield; #endif static struct reader_registry *registry; +static char __thread need_mb; static int num_readers, alloc_readers; -#ifndef DEBUG_FULL_MB -static int sig_done; -#endif void internal_urcu_lock(void) { -#if 0 int ret; - /* Mutex sleeping does not play well with busy-waiting loop. */ + +#ifndef DISTRUST_SIGNALS_EXTREME ret = pthread_mutex_lock(&urcu_mutex); if (ret) { perror("Error in pthread mutex lock"); exit(-1); } -#endif - while (pthread_mutex_trylock(&urcu_mutex) != 0) - cpu_relax(); +#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(); + } + poll(NULL,0,10); + } +#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ } void internal_urcu_unlock(void) @@ -87,38 +117,42 @@ static void switch_next_urcu_qparity(void) } #ifdef DEBUG_FULL_MB -static void force_mb_single_thread(pthread_t tid) +#ifdef HAS_INCOHERENT_CACHES +static void force_mb_single_thread(struct reader_registry *index) { smp_mb(); } +#endif /* #ifdef HAS_INCOHERENT_CACHES */ static void force_mb_all_threads(void) { smp_mb(); } -#else - -static void force_mb_single_thread(pthread_t tid) +#else /* #ifdef DEBUG_FULL_MB */ +#ifdef HAS_INCOHERENT_CACHES +static void force_mb_single_thread(struct reader_registry *index) { assert(registry); - sig_done = 0; /* * 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. - * smp_mb(); write sig_done before sending the signals */ - smp_mc(); /* write sig_done before sending the signals */ - pthread_kill(tid, SIGURCU); + *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 (LOAD_SHARED(sig_done) < 1) - cpu_relax(); - smp_mb(); /* read sig_done before ending the barrier */ + while (*index->need_mb) { + poll(NULL, 0, 1); + } + smp_mb(); /* read ->need_mb before ending the barrier */ } +#endif /* #ifdef HAS_INCOHERENT_CACHES */ static void force_mb_all_threads(void) { @@ -129,26 +163,39 @@ static void force_mb_all_threads(void) */ if (!registry) return; - sig_done = 0; /* * 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. - * smp_mb(); write sig_done before sending the signals */ - smp_mc(); /* write sig_done before sending the signals */ - for (index = registry; index < registry + num_readers; index++) + 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); + } /* * Wait for sighandler (and thus mb()) to execute on every thread. - * BUSY-LOOP. + * + * Note that the pthread_kill() will never be executed on systems + * that correctly deliver signals in a timely manner. However, it + * is not uncommon for kernels to have bugs that can result in + * lost or unduly delayed signals. + * + * If you are seeing the below pthread_kill() executing much at + * all, we suggest testing the underlying kernel and filing the + * relevant bug report. For Linux kernels, we recommend getting + * the Linux Test Project (LTP). */ - while (LOAD_SHARED(sig_done) < num_readers) - cpu_relax(); - smp_mb(); /* read sig_done before ending the barrier */ + for (index = registry; index < registry + num_readers; index++) { + while (*index->need_mb) { + pthread_kill(index->tid, SIGURCU); + poll(NULL, 0, 1); + } + } + smp_mb(); /* read ->need_mb before ending the barrier */ } -#endif +#endif /* #else #ifdef DEBUG_FULL_MB */ void wait_for_quiescent_state(void) { @@ -160,6 +207,10 @@ void wait_for_quiescent_state(void) * Wait for each thread urcu_active_readers count to become 0. */ for (index = registry; index < registry + num_readers; index++) { +#ifndef HAS_INCOHERENT_CACHES + while (rcu_old_gp_ongoing(index->urcu_active_readers)) + cpu_relax(); +#else /* #ifndef HAS_INCOHERENT_CACHES */ int wait_loops = 0; /* * BUSY-LOOP. Force the reader thread to commit its @@ -167,12 +218,13 @@ void wait_for_quiescent_state(void) */ while (rcu_old_gp_ongoing(index->urcu_active_readers)) { if (wait_loops++ == KICK_READER_LOOPS) { - force_mb_single_thread(index->tid); + force_mb_single_thread(index); wait_loops = 0; } else { cpu_relax(); } } +#endif /* #else #ifndef HAS_INCOHERENT_CACHES */ } } @@ -232,7 +284,47 @@ void synchronize_rcu(void) internal_urcu_unlock(); } -void urcu_add_reader(pthread_t id) +/* + * 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(); +} + +void *rcu_dereference(void *p) +{ + return _rcu_dereference(p); +} + +void *rcu_assign_pointer_sym(void **p, void *v) +{ + wmb(); + return STORE_SHARED(p, v); +} + +void *rcu_xchg_pointer_sym(void **p, void *v) +{ + wmb(); + return xchg(p, v); +} + +void *rcu_publish_content_sym(void **p, void *v) +{ + void *oldptr; + + oldptr = _rcu_xchg_pointer(p, v); + synchronize_rcu(); + return oldptr; +} + +static void rcu_add_reader(pthread_t id) { struct reader_registry *oldarray; @@ -254,6 +346,7 @@ void urcu_add_reader(pthread_t id) 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++; } @@ -261,7 +354,7 @@ void urcu_add_reader(pthread_t id) * Never shrink (implementation limitation). * This is O(nb threads). Eventually use a hash table. */ -void urcu_remove_reader(pthread_t id) +static void rcu_remove_reader(pthread_t id) { struct reader_registry *index; @@ -280,22 +373,22 @@ void urcu_remove_reader(pthread_t id) assert(0); } -void urcu_register_thread(void) +void rcu_register_thread(void) { internal_urcu_lock(); - urcu_add_reader(pthread_self()); + rcu_add_reader(pthread_self()); internal_urcu_unlock(); } -void urcu_unregister_thread(void) +void rcu_unregister_thread(void) { internal_urcu_lock(); - urcu_remove_reader(pthread_self()); + rcu_remove_reader(pthread_self()); internal_urcu_unlock(); } #ifndef DEBUG_FULL_MB -void sigurcu_handler(int signo, siginfo_t *siginfo, void *context) +static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context) { /* * Executing this smp_mb() is the only purpose of this signal handler. @@ -303,7 +396,8 @@ void sigurcu_handler(int signo, siginfo_t *siginfo, void *context) * executed on. */ smp_mb(); - atomic_inc(&sig_done); + need_mb = 0; + smp_mb(); } void __attribute__((constructor)) urcu_init(void) @@ -332,4 +426,4 @@ void __attribute__((destructor)) urcu_exit(void) assert(act.sa_sigaction == sigurcu_handler); free(registry); } -#endif +#endif /* #ifndef DEBUG_FULL_MB */