X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-qsbr.c;h=87c83d7fc154443dcee6329cb75abe2a97c33f8e;hp=fd0ebf6c4a710ae2bed98e6a919f424eb05bc992;hb=2a67ec322b40544b9e4fc5f138629a65b4f20352;hpb=9f1621ca8d6ce9178343ae24aeef406c0ac2564a diff --git a/urcu-qsbr.c b/urcu-qsbr.c index fd0ebf6..87c83d7 100644 --- a/urcu-qsbr.c +++ b/urcu-qsbr.c @@ -32,14 +32,9 @@ #include #include -#include "urcu-static.h" +#include "urcu-qsbr.h" /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ -#include "urcu.h" - -void __attribute__((constructor)) urcu_init(void); -void __attribute__((destructor)) urcu_exit(void); - -int init_done; +//#include "urcu.h" pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER; @@ -52,14 +47,14 @@ long urcu_gp_ctr = 0; * Written to only by each individual reader. Read by both the reader and the * writers. */ -long __thread urcu_active_readers; +long __thread rcu_reader_qs_gp; /* Thread IDs of registered readers */ #define INIT_NUM_THREADS 4 struct reader_registry { pthread_t tid; - long *urcu_active_readers; + long *rcu_reader_qs_gp; char *need_mb; }; @@ -110,7 +105,6 @@ void internal_urcu_unlock(void) } } -#ifdef DEBUG_FULL_MB #ifdef HAS_INCOHERENT_CACHES static void force_mb_single_thread(struct reader_registry *index) { @@ -122,74 +116,6 @@ static void force_mb_all_threads(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 */ - -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 - * compiler barriers around rcu read lock as real memory barriers. - */ - if (!registry) - return; - /* - * 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. - */ - 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. - * - * 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). - */ - 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 /* #else #ifdef DEBUG_FULL_MB */ void wait_for_quiescent_state(void) { @@ -198,19 +124,21 @@ void wait_for_quiescent_state(void) if (!registry) return; /* - * Wait for each thread urcu_active_readers count to become 0. + * Wait for each thread rcu_reader_qs_gp 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)) + while (rcu_gp_ongoing(index->rcu_reader_qs_gp) && + (*index->rcu_reader_qs_gp - urcu_gp_ctr < 0)) cpu_relax(); #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. + * rcu_reader_qs_gp update to memory if we wait for too long. */ - while (rcu_old_gp_ongoing(index->urcu_active_readers)) { + while (rcu_gp_ongoing(index->rcu_reader_qs_gp) && + (*index->rcu_reader_qs_gp - urcu_gp_ctr < 0)) { if (wait_loops++ == KICK_READER_LOOPS) { force_mb_single_thread(index); wait_loops = 0; @@ -293,7 +221,7 @@ static void rcu_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].rcu_reader_qs_gp = &rcu_reader_qs_gp; registry[num_readers].need_mb = &need_mb; num_readers++; } @@ -312,7 +240,7 @@ static void rcu_remove_reader(pthread_t 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; + registry[num_readers - 1].rcu_reader_qs_gp = NULL; num_readers--; return; } @@ -324,67 +252,18 @@ static void rcu_remove_reader(pthread_t id) void rcu_register_thread(void) { internal_urcu_lock(); - urcu_init(); /* In case gcc does not support constructor attribute */ rcu_add_reader(pthread_self()); internal_urcu_unlock(); } void rcu_unregister_thread(void) { + /* + * We have to make the thread offline otherwise we end up dealocking + * with a waiting writer. + */ + _rcu_thread_offline(); internal_urcu_lock(); rcu_remove_reader(pthread_self()); internal_urcu_unlock(); } - -#ifndef DEBUG_FULL_MB -static void sigurcu_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 - * executed on. - */ - smp_mb(); - need_mb = 0; - smp_mb(); -} - -/* - * urcu_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 internal_urcu_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 urcu_init(void) -{ - struct sigaction act; - int ret; - - if (init_done) - return; - init_done = 1; - - act.sa_sigaction = sigurcu_handler; - ret = sigaction(SIGURCU, &act, NULL); - if (ret) { - perror("Error in sigaction"); - exit(-1); - } -} - -void urcu_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); -} -#endif /* #ifndef DEBUG_FULL_MB */