X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=a78c02bdca6a71f9e7f66c76295fc8f1f33cdd37;hp=77f6888f0ec547647fe8ced21e04d19e4de73105;hb=882f335739b978d1c55be2faeed077f315afe5d7;hpb=1f689e13ea7e519b1afc001e9c55a7b1b60b599f diff --git a/urcu.c b/urcu.c index 77f6888..a78c02b 100644 --- a/urcu.c +++ b/urcu.c @@ -36,10 +36,14 @@ #include #include -#include "urcu/wfqueue.h" +#include "urcu/wfcqueue.h" #include "urcu/map/urcu.h" #include "urcu/static/urcu.h" #include "urcu-pointer.h" +#include "urcu/tls-compat.h" + +#include "urcu-die.h" +#include "urcu-wait.h" /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ #undef _LGPL_SOURCE @@ -60,7 +64,7 @@ #ifdef RCU_MEMBARRIER static int init_done; -int has_sys_membarrier; +int rcu_has_sys_membarrier; void __attribute__((constructor)) rcu_init(void); #endif @@ -80,7 +84,7 @@ void __attribute__((destructor)) rcu_exit(void); static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; -int32_t gp_futex; +int32_t rcu_gp_futex; /* * Global grace period counter. @@ -94,35 +98,36 @@ unsigned long rcu_gp_ctr = RCU_GP_COUNT; * Written to only by each individual reader. Read by both the reader and the * writers. */ -struct rcu_reader __thread rcu_reader; +DEFINE_URCU_TLS(struct rcu_reader, rcu_reader); #ifdef DEBUG_YIELD -unsigned int yield_active; -unsigned int __thread rand_yield; +unsigned int rcu_yield_active; +DEFINE_URCU_TLS(unsigned int, rcu_rand_yield); #endif static CDS_LIST_HEAD(registry); +/* + * Queue keeping threads awaiting to wait for a grace period. Contains + * struct gp_waiters_thread objects. + */ +static DEFINE_URCU_WAIT_QUEUE(gp_waiters); + static void mutex_lock(pthread_mutex_t *mutex) { int ret; #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 (CMM_LOAD_SHARED(rcu_reader.need_mb)) { + if (ret != EBUSY && ret != EINTR) + urcu_die(ret); + if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { cmm_smp_mb(); - _CMM_STORE_SHARED(rcu_reader.need_mb, 0); + _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); cmm_smp_mb(); } poll(NULL,0,10); @@ -135,16 +140,14 @@ 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 static void smp_mb_master(int group) { - if (likely(has_sys_membarrier)) + if (caa_likely(rcu_has_sys_membarrier)) membarrier(MEMBARRIER_EXPEDITED); else cmm_smp_mb(); @@ -214,58 +217,60 @@ static void wait_gp(void) { /* Read reader_gp before read futex */ smp_mb_master(RCU_MB_GROUP); - if (uatomic_read(&gp_futex) == -1) - futex_async(&gp_futex, FUTEX_WAIT, -1, + if (uatomic_read(&rcu_gp_futex) == -1) + futex_async(&rcu_gp_futex, FUTEX_WAIT, -1, NULL, NULL, 0); } -void update_counter_and_wait(void) +static void wait_for_readers(struct cds_list_head *input_readers, + struct cds_list_head *cur_snap_readers, + struct cds_list_head *qsreaders) { - CDS_LIST_HEAD(qsreaders); int wait_loops = 0; struct rcu_reader *index, *tmp; - /* Switch parity: 0 -> 1, 1 -> 0 */ - CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); - - /* - * Must commit rcu_gp_ctr update to memory before waiting for quiescent - * state. Failure to do so could result in the writer waiting forever - * while new readers are always accessing data (no progress). Enforce - * compiler-order of store to rcu_gp_ctr before load rcu_reader ctr. - */ - cmm_barrier(); - - /* - * - * Adding a cmm_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. - */ - cmm_smp_mb(); - /* - * Wait for each thread rcu_reader.ctr count to become 0. + * Wait for each thread URCU_TLS(rcu_reader).ctr to either + * indicate quiescence (not nested), or observe the current + * rcu_gp_ctr value. */ for (;;) { wait_loops++; if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { - uatomic_dec(&gp_futex); + uatomic_dec(&rcu_gp_futex); /* Write futex before read reader_gp */ smp_mb_master(RCU_MB_GROUP); } - cds_list_for_each_entry_safe(index, tmp, ®istry, node) { - if (!rcu_gp_ongoing(&index->ctr)) - cds_list_move(&index->node, &qsreaders); + cds_list_for_each_entry_safe(index, tmp, input_readers, node) { + switch (rcu_reader_state(&index->ctr)) { + case RCU_READER_ACTIVE_CURRENT: + if (cur_snap_readers) { + cds_list_move(&index->node, + cur_snap_readers); + break; + } + /* Fall-through */ + case RCU_READER_INACTIVE: + cds_list_move(&index->node, qsreaders); + break; + case RCU_READER_ACTIVE_OLD: + /* + * Old snapshot. Leaving node in + * input_readers will make us busy-loop + * until the snapshot becomes current or + * the reader becomes inactive. + */ + break; + } } #ifndef HAS_INCOHERENT_CACHES - if (cds_list_empty(®istry)) { + if (cds_list_empty(input_readers)) { if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { /* Read reader_gp before write futex */ smp_mb_master(RCU_MB_GROUP); - uatomic_set(&gp_futex, 0); + uatomic_set(&rcu_gp_futex, 0); } break; } else { @@ -277,13 +282,14 @@ void update_counter_and_wait(void) #else /* #ifndef HAS_INCOHERENT_CACHES */ /* * BUSY-LOOP. Force the reader thread to commit its - * rcu_reader.ctr update to memory if we wait for too long. + * URCU_TLS(rcu_reader).ctr update to memory if we wait + * for too long. */ - if (cds_list_empty(®istry)) { + if (cds_list_empty(input_readers)) { if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { /* Read reader_gp before write futex */ smp_mb_master(RCU_MB_GROUP); - uatomic_set(&gp_futex, 0); + uatomic_set(&rcu_gp_futex, 0); } break; } else { @@ -301,14 +307,40 @@ void update_counter_and_wait(void) } #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ } - /* put back the reader list in the registry */ - cds_list_splice(&qsreaders, ®istry); } void synchronize_rcu(void) { + CDS_LIST_HEAD(cur_snap_readers); + CDS_LIST_HEAD(qsreaders); + DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); + struct urcu_waiters waiters; + + /* + * Add ourself to gp_waiters queue of threads awaiting to wait + * for a grace period. Proceed to perform the grace period only + * if we are the first thread added into the queue. + * The implicit memory barrier before urcu_wait_add() + * orders prior memory accesses of threads put into the wait + * queue before their insertion into the wait queue. + */ + if (urcu_wait_add(&gp_waiters, &wait) != 0) { + /* Not first in queue: will be awakened by another thread. */ + urcu_adaptative_busy_wait(&wait); + /* Order following memory accesses after grace period. */ + cmm_smp_mb(); + return; + } + /* We won't need to wake ourself up */ + urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); + mutex_lock(&rcu_gp_lock); + /* + * Move all waiters into our local queue. + */ + urcu_move_waiters(&waiters, &gp_waiters); + if (cds_list_empty(®istry)) goto out; @@ -319,20 +351,39 @@ void synchronize_rcu(void) smp_mb_master(RCU_MB_GROUP); /* - * Wait for previous parity to be empty of readers. + * Wait for readers to observe original parity or be quiescent. */ - update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ + wait_for_readers(®istry, &cur_snap_readers, &qsreaders); /* - * Must finish waiting for quiescent state for parity 0 before + * Must finish waiting for quiescent state for original parity before * committing next rcu_gp_ctr update to memory. Failure to do so could * result in the writer waiting forever while new readers are always * accessing data (no progress). Enforce compiler-order of load - * rcu_reader ctr before store to rcu_gp_ctr. + * URCU_TLS(rcu_reader).ctr before store to rcu_gp_ctr. + */ + cmm_barrier(); + + /* + * Adding a cmm_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. + */ + cmm_smp_mb(); + + /* Switch parity: 0 -> 1, 1 -> 0 */ + CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); + + /* + * Must commit rcu_gp_ctr update to memory before waiting for quiescent + * state. Failure to do so could result in the writer waiting forever + * while new readers are always accessing data (no progress). Enforce + * compiler-order of store to rcu_gp_ctr before load rcu_reader ctr. */ cmm_barrier(); /* + * * Adding a cmm_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. @@ -340,9 +391,14 @@ void synchronize_rcu(void) cmm_smp_mb(); /* - * Wait for previous parity to be empty of readers. + * Wait for readers to observe new parity or be quiescent. */ - update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ + wait_for_readers(&cur_snap_readers, NULL, &qsreaders); + + /* + * Put quiescent reader list back into registry. + */ + cds_list_splice(&qsreaders, ®istry); /* Finish waiting for reader threads before letting the old ptr being * freed. Must be done within rcu_gp_lock because it iterates on reader @@ -350,6 +406,13 @@ void synchronize_rcu(void) smp_mb_master(RCU_MB_GROUP); out: mutex_unlock(&rcu_gp_lock); + + /* + * Wakeup waiters only after we have completed the grace period + * and have ensured the memory barriers at the end of the grace + * period have been issued. + */ + urcu_wake_all_waiters(&waiters); } /* @@ -366,22 +429,27 @@ void rcu_read_unlock(void) _rcu_read_unlock(); } +int rcu_read_ongoing(void) +{ + return _rcu_read_ongoing(); +} + void rcu_register_thread(void) { - rcu_reader.tid = pthread_self(); - assert(rcu_reader.need_mb == 0); - assert(!(rcu_reader.ctr & RCU_GP_CTR_NEST_MASK)); + URCU_TLS(rcu_reader).tid = pthread_self(); + assert(URCU_TLS(rcu_reader).need_mb == 0); + assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); mutex_lock(&rcu_gp_lock); rcu_init(); /* In case gcc does not support constructor attribute */ - cds_list_add(&rcu_reader.node, ®istry); + cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); mutex_unlock(&rcu_gp_lock); } void rcu_unregister_thread(void) { mutex_lock(&rcu_gp_lock); - cds_list_del(&rcu_reader.node); + cds_list_del(&URCU_TLS(rcu_reader).node); mutex_unlock(&rcu_gp_lock); } @@ -392,7 +460,7 @@ void rcu_init(void) return; init_done = 1; if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY)) - has_sys_membarrier = 1; + rcu_has_sys_membarrier = 1; } #endif @@ -405,7 +473,7 @@ static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) * executed on. */ cmm_smp_mb(); - _CMM_STORE_SHARED(rcu_reader.need_mb, 0); + _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); cmm_smp_mb(); } @@ -430,10 +498,8 @@ 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) @@ -442,15 +508,15 @@ 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)); } #endif /* #ifdef RCU_SIGNAL */ +DEFINE_RCU_FLAVOR(rcu_flavor); + #include "urcu-call-rcu-impl.h" #include "urcu-defer-impl.h"