X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=337f7640b44d208855277f6fc53d9322f212d638;hp=475b4d1c991a00832409ae7332e6317442b1f042;hb=ad7de003b45b3a7339b90208c321517c2dcbdc3e;hpb=0a52082baa5dd26455966c42a96f3185767590b7 diff --git a/urcu.c b/urcu.c index 475b4d1..337f764 100644 --- a/urcu.c +++ b/urcu.c @@ -6,6 +6,8 @@ * Copyright February 2009 - Mathieu Desnoyers * * Distributed under GPLv2 + * + * IBM's contributions to this file may be relicensed under LGPLv2 or later. */ #include @@ -14,6 +16,8 @@ #include #include #include +#include +#include #include "urcu.h" @@ -39,6 +43,7 @@ long __thread urcu_active_readers; struct reader_registry { pthread_t tid; long *urcu_active_readers; + char *need_mb; }; #ifdef DEBUG_YIELD @@ -47,24 +52,34 @@ 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 +102,42 @@ 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 +148,39 @@ 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 +192,10 @@ 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 +203,13 @@ 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 */ } } @@ -254,6 +291,7 @@ 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++; } @@ -303,7 +341,8 @@ 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 +371,4 @@ void __attribute__((destructor)) urcu_exit(void) assert(act.sa_sigaction == sigurcu_handler); free(registry); } -#endif +#endif /* #ifndef DEBUG_FULL_MB */