X-Git-Url: http://git.liburcu.org/?p=userspace-rcu.git;a=blobdiff_plain;f=urcu.c;h=e9df01bc7b56cdb25b6e225e6ba46d2182ab28be;hp=5fb4db8229eb2f8c4ac4893d9684d1401ed6e42b;hb=refs%2Fheads%2Fstable-0.7;hpb=bd252a04bbbb163aa4d8864b1e1e5a3a4d9d0892 diff --git a/urcu.c b/urcu.c index 5fb4db8..e9df01b 100644 --- a/urcu.c +++ b/urcu.c @@ -26,6 +26,7 @@ #define _BSD_SOURCE #define _GNU_SOURCE #define _LGPL_SOURCE +#define _DEFAULT_SOURCE #include #include #include @@ -42,6 +43,8 @@ #include "urcu-pointer.h" #include "urcu/tls-compat.h" +#include "urcu-die.h" + /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ #undef _LGPL_SOURCE #include "urcu.h" @@ -50,9 +53,9 @@ /* * 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 a few loops waiting for it. + * per-se), kick it after 10 loops waiting for it. */ -#define KICK_READER_LOOPS 10000 +#define KICK_READER_LOOPS 10 /* * Active attempts to check for reader Q.S. before calling futex(). @@ -79,7 +82,21 @@ void __attribute__((constructor)) rcu_init(void); void __attribute__((destructor)) rcu_exit(void); #endif +/* + * 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; int32_t gp_futex; @@ -90,16 +107,15 @@ int32_t gp_futex; * Written to only by writer with mutex taken. Read by both writer and readers. */ unsigned long 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); +__DEFINE_URCU_TLS_GLOBAL(struct rcu_reader, rcu_reader); #ifdef DEBUG_YIELD unsigned int yield_active; -DEFINE_URCU_TLS(unsigned int, rand_yield); +__DEFINE_URCU_TLS_GLOBAL(unsigned int, rand_yield); #endif static CDS_LIST_HEAD(registry); @@ -110,17 +126,12 @@ static void mutex_lock(pthread_mutex_t *mutex) #ifndef DISTRUST_SIGNALS_EXTREME ret = pthread_mutex_lock(mutex); - if (ret) { - perror("Error in pthread mutex lock"); - exit(-1); - } + if (ret) + urcu_die(ret); #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ 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"); - exit(-1); - } + 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); @@ -136,10 +147,8 @@ static void mutex_unlock(pthread_mutex_t *mutex) int ret; ret = pthread_mutex_unlock(mutex); - if (ret) { - perror("Error in pthread mutex unlock"); - exit(-1); - } + if (ret) + urcu_die(ret); } #ifdef RCU_MEMBARRIER @@ -210,21 +219,54 @@ static void smp_mb_master(int group) /* * synchronize_rcu() waiting. Single thread. + * Always called with rcu_registry lock held. Releases this lock and + * grabs it again. Holds the lock when it returns. */ static void wait_gp(void) { - /* Read reader_gp before read futex */ + /* + * Read reader_gp before read futex. smp_mb_master() needs to + * be called with the rcu registry lock held in RCU_SIGNAL + * flavor. + */ smp_mb_master(RCU_MB_GROUP); - if (uatomic_read(&gp_futex) == -1) - futex_async(&gp_futex, FUTEX_WAIT, -1, - NULL, NULL, 0); + /* Temporarily unlock the registry lock. */ + mutex_unlock(&rcu_registry_lock); + if (uatomic_read(&gp_futex) != -1) + goto end; + while (futex_async(&gp_futex, FUTEX_WAIT, -1, + NULL, NULL, 0)) { + switch (errno) { + case EWOULDBLOCK: + /* Value already changed. */ + goto end; + case EINTR: + /* Retry if interrupted by signal. */ + break; /* Get out of switch. */ + default: + /* Unexpected error. */ + urcu_die(errno); + } + } +end: + /* + * Re-lock the registry lock before the next loop. + */ + mutex_lock(&rcu_registry_lock); } +/* + * Always called with rcu_registry lock held. Releases this lock between + * iterations and grabs it again. Holds the lock when it returns. + */ void update_counter_and_wait(void) { CDS_LIST_HEAD(qsreaders); - int wait_loops = 0; + unsigned int wait_loops = 0; struct rcu_reader *index, *tmp; +#ifdef HAS_INCOHERENT_CACHES + unsigned int wait_gp_loops = 0; +#endif /* HAS_INCOHERENT_CACHES */ /* Switch parity: 0 -> 1, 1 -> 0 */ CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); @@ -249,8 +291,9 @@ void update_counter_and_wait(void) * Wait for each thread URCU_TLS(rcu_reader).ctr count to become 0. */ for (;;) { - wait_loops++; - if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { + if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) + wait_loops++; + if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { uatomic_dec(&gp_futex); /* Write futex before read reader_gp */ smp_mb_master(RCU_MB_GROUP); @@ -263,17 +306,26 @@ void update_counter_and_wait(void) #ifndef HAS_INCOHERENT_CACHES if (cds_list_empty(®istry)) { - if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { + if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { /* Read reader_gp before write futex */ smp_mb_master(RCU_MB_GROUP); uatomic_set(&gp_futex, 0); } break; } else { - if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) + if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { + /* wait_gp unlocks/locks registry lock. */ wait_gp(); - else + } else { + /* Temporarily unlock the registry lock. */ + mutex_unlock(&rcu_registry_lock); caa_cpu_relax(); + /* + * Re-lock the registry lock before the + * next loop. + */ + mutex_lock(&rcu_registry_lock); + } } #else /* #ifndef HAS_INCOHERENT_CACHES */ /* @@ -282,23 +334,30 @@ void update_counter_and_wait(void) * for too long. */ if (cds_list_empty(®istry)) { - if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { + if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { /* Read reader_gp before write futex */ smp_mb_master(RCU_MB_GROUP); uatomic_set(&gp_futex, 0); } break; } else { - switch (wait_loops) { - case RCU_QS_ACTIVE_ATTEMPTS: - wait_gp(); - break; /* only escape switch */ - case KICK_READER_LOOPS: + if (wait_gp_loops == KICK_READER_LOOPS) { smp_mb_master(RCU_MB_GROUP); - wait_loops = 0; - break; /* only escape switch */ - default: + wait_gp_loops = 0; + } + if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { + /* wait_gp unlocks/locks registry lock. */ + wait_gp(); + wait_gp_loops++; + } else { + /* Temporarily unlock the registry lock. */ + mutex_unlock(&rcu_registry_lock); caa_cpu_relax(); + /* + * Re-lock the registry lock before the + * next loop. + */ + mutex_lock(&rcu_registry_lock); } } #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ @@ -310,18 +369,23 @@ void update_counter_and_wait(void) void synchronize_rcu(void) { mutex_lock(&rcu_gp_lock); + 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_gp_lock because it - * iterates on reader threads.*/ + /* + * 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 */ smp_mb_master(RCU_MB_GROUP); /* * Wait for previous parity to be empty of readers. + * update_counter_and_wait() can release and grab again + * rcu_registry_lock interally. */ update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ @@ -343,14 +407,19 @@ void synchronize_rcu(void) /* * Wait for previous parity to be empty of readers. + * update_counter_and_wait() can release and grab again + * rcu_registry_lock interally. */ 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 rcu_gp_lock because it iterates on reader - * 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); } @@ -374,17 +443,17 @@ void rcu_register_thread(void) assert(URCU_TLS(rcu_reader).need_mb == 0); assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); - mutex_lock(&rcu_gp_lock); + 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_gp_lock); + mutex_unlock(&rcu_registry_lock); } void rcu_unregister_thread(void) { - mutex_lock(&rcu_gp_lock); + mutex_lock(&rcu_registry_lock); cds_list_del(&URCU_TLS(rcu_reader).node); - mutex_unlock(&rcu_gp_lock); + mutex_unlock(&rcu_registry_lock); } #ifdef RCU_MEMBARRIER @@ -415,9 +484,9 @@ 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 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. + * 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) { @@ -432,10 +501,8 @@ void rcu_init(void) act.sa_flags = SA_SIGINFO | SA_RESTART; sigemptyset(&act.sa_mask); ret = sigaction(SIGRCU, &act, NULL); - if (ret) { - perror("Error in sigaction"); - exit(-1); - } + if (ret) + urcu_die(errno); } void rcu_exit(void) @@ -444,10 +511,8 @@ void rcu_exit(void) int ret; ret = sigaction(SIGRCU, NULL, &act); - if (ret) { - perror("Error in sigaction"); - exit(-1); - } + if (ret) + urcu_die(errno); assert(act.sa_sigaction == sigrcu_handler); assert(cds_list_empty(®istry)); }