X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=ffdab3c2fc1eacbad2c4e73f5e89e83261fdb8d5;hp=b8e8b422a5941adab6999979736317a29e2d51f9;hb=32c15e4e6fa2c368f4649d904c91e4293a1193e3;hpb=f0708810fe66d7fdcf52903c607ed65c9fa664c7 diff --git a/urcu.c b/urcu.c index b8e8b42..ffdab3c 100644 --- a/urcu.c +++ b/urcu.c @@ -57,7 +57,7 @@ void __attribute__((constructor)) rcu_init(void); void __attribute__((destructor)) rcu_exit(void); #endif -static pthread_mutex_t rcu_mutex = PTHREAD_MUTEX_INITIALIZER; +static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; int gp_futex; @@ -82,18 +82,18 @@ unsigned int __thread rand_yield; static LIST_HEAD(registry); -static void internal_rcu_lock(void) +static void mutex_lock(pthread_mutex_t *mutex) { int ret; #ifndef DISTRUST_SIGNALS_EXTREME - ret = pthread_mutex_lock(&rcu_mutex); + 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(&rcu_mutex)) != 0) { + 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"); @@ -109,25 +109,17 @@ static void internal_rcu_lock(void) #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ } -static void internal_rcu_unlock(void) +static void mutex_unlock(pthread_mutex_t *mutex) { int ret; - ret = pthread_mutex_unlock(&rcu_mutex); + ret = pthread_mutex_unlock(mutex); if (ret) { perror("Error in pthread mutex unlock"); exit(-1); } } -/* - * called with rcu_mutex held. - */ -static void switch_next_rcu_qparity(void) -{ - STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); -} - #ifdef RCU_MEMBARRIER static void smp_mb_heavy(void) { @@ -207,14 +199,29 @@ static void wait_gp(void) NULL, NULL, 0); } -void wait_for_quiescent_state(void) +void update_counter_and_wait(void) { LIST_HEAD(qsreaders); int wait_loops = 0; struct rcu_reader *index, *tmp; - if (list_empty(®istry)) - return; + /* Switch parity: 0 -> 1, 1 -> 0 */ + 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 STORE_SHARED and LOAD_SHARED. + */ + + /* + * Adding a 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. + */ + smp_mb(); + /* * Wait for each thread rcu_reader.ctr count to become 0. */ @@ -278,35 +285,21 @@ void wait_for_quiescent_state(void) void synchronize_rcu(void) { - internal_rcu_lock(); + mutex_lock(&rcu_gp_lock); + + if (list_empty(®istry)) + goto out; /* All threads should read qparity before accessing data structure - * where new ptr points to. Must be done within internal_rcu_lock - * because it iterates on reader threads.*/ + * where new ptr points to. Must be done within rcu_gp_lock because it + * iterates on reader threads.*/ /* Write new ptr before changing the qparity */ smp_mb_heavy(); - switch_next_rcu_qparity(); /* 0 -> 1 */ - - /* - * 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. - */ - - /* - * Adding a 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. - */ - smp_mb(); - /* * Wait for previous parity to be empty of readers. */ - wait_for_quiescent_state(); /* Wait readers in parity 0 */ + update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ /* * Must finish waiting for quiescent state for parity 0 before @@ -323,34 +316,17 @@ void synchronize_rcu(void) */ smp_mb(); - switch_next_rcu_qparity(); /* 1 -> 0 */ - - /* - * 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. - */ - - /* - * Adding a 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. - */ - smp_mb(); - /* * Wait for previous parity to be empty of readers. */ - wait_for_quiescent_state(); /* Wait readers in parity 1 */ + update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ /* Finish waiting for reader threads before letting the old ptr being - * freed. Must be done within internal_rcu_lock because it iterates on - * reader threads. */ + * freed. Must be done within rcu_gp_lock because it iterates on reader + * threads. */ smp_mb_heavy(); - - internal_rcu_unlock(); +out: + mutex_unlock(&rcu_gp_lock); } /* @@ -373,17 +349,17 @@ void rcu_register_thread(void) assert(rcu_reader.need_mb == 0); assert(rcu_reader.ctr == 0); - internal_rcu_lock(); + mutex_lock(&rcu_gp_lock); rcu_init(); /* In case gcc does not support constructor attribute */ list_add(&rcu_reader.head, ®istry); - internal_rcu_unlock(); + mutex_unlock(&rcu_gp_lock); } void rcu_unregister_thread(void) { - internal_rcu_lock(); + mutex_lock(&rcu_gp_lock); list_del(&rcu_reader.head); - internal_rcu_unlock(); + mutex_unlock(&rcu_gp_lock); } #ifdef RCU_MEMBARRIER @@ -392,7 +368,7 @@ void rcu_init(void) if (init_done) return; init_done = 1; - if (!membarrier(MEMBARRIER_EXPEDITED)) + if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY)) has_sys_membarrier = 1; } #endif @@ -414,9 +390,9 @@ static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) * 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 internal_rcu_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. + * holing the rcu_gp_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) {