X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=a78c02bdca6a71f9e7f66c76295fc8f1f33cdd37;hp=a3ceca3f5263be7812288f4e909eed6878246980;hb=882f335739b978d1c55be2faeed077f315afe5d7;hpb=0d342f2fb06c0b2e37a34b0968d1dc26e2220825 diff --git a/urcu.c b/urcu.c index a3ceca3..a78c02b 100644 --- a/urcu.c +++ b/urcu.c @@ -3,7 +3,7 @@ * * Userspace RCU library * - * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Mathieu Desnoyers * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. * * This library is free software; you can redistribute it and/or @@ -24,22 +24,47 @@ */ #define _BSD_SOURCE +#define _GNU_SOURCE +#define _LGPL_SOURCE #include #include #include #include #include +#include #include #include #include -#include "urcu-static.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 #include "urcu.h" +#define _LGPL_SOURCE + +/* + * 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. + */ +#define KICK_READER_LOOPS 10000 + +/* + * Active attempts to check for reader Q.S. before calling futex(). + */ +#define RCU_QS_ACTIVE_ATTEMPTS 100 #ifdef RCU_MEMBARRIER static int init_done; -int has_sys_membarrier; +int rcu_has_sys_membarrier; void __attribute__((constructor)) rcu_init(void); #endif @@ -59,7 +84,7 @@ void __attribute__((destructor)) rcu_exit(void); static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; -int gp_futex; +int32_t rcu_gp_futex; /* * Global grace period counter. @@ -73,14 +98,20 @@ 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 LIST_HEAD(registry); +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) { @@ -88,21 +119,16 @@ 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 (LOAD_SHARED(rcu_reader.need_mb)) { - smp_mb(); - _STORE_SHARED(rcu_reader.need_mb, 0); - smp_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(URCU_TLS(rcu_reader).need_mb, 0); + cmm_smp_mb(); } poll(NULL,0,10); } @@ -114,26 +140,24 @@ 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 - smp_mb(); + cmm_smp_mb(); } #endif #ifdef RCU_MB static void smp_mb_master(int group) { - smp_mb(); + cmm_smp_mb(); } #endif @@ -143,19 +167,19 @@ static void force_mb_all_readers(void) struct rcu_reader *index; /* - * Ask for each threads to execute a smp_mb() so we can consider the + * Ask for each threads to execute a cmm_smp_mb() so we can consider the * compiler barriers around rcu read lock as real memory barriers. */ - if (list_empty(®istry)) + if (cds_list_empty(®istry)) return; /* - * pthread_kill has a smp_mb(). But beware, we assume it performs + * pthread_kill has a cmm_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 + * safe and don't assume anything : we use cmm_smp_mc() to make sure the * cache flush is enforced. */ - list_for_each_entry(index, ®istry, head) { - STORE_SHARED(index->need_mb, 1); + cds_list_for_each_entry(index, ®istry, node) { + CMM_STORE_SHARED(index->need_mb, 1); pthread_kill(index->tid, SIGRCU); } /* @@ -171,13 +195,13 @@ static void force_mb_all_readers(void) * relevant bug report. For Linux kernels, we recommend getting * the Linux Test Project (LTP). */ - list_for_each_entry(index, ®istry, head) { - while (LOAD_SHARED(index->need_mb)) { + cds_list_for_each_entry(index, ®istry, node) { + while (CMM_LOAD_SHARED(index->need_mb)) { pthread_kill(index->tid, SIGRCU); poll(NULL, 0, 1); } } - smp_mb(); /* read ->need_mb before ending the barrier */ + cmm_smp_mb(); /* read ->need_mb before ending the barrier */ } static void smp_mb_master(int group) @@ -193,74 +217,79 @@ 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) { - LIST_HEAD(qsreaders); int wait_loops = 0; struct rcu_reader *index, *tmp; - /* 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. + * 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); } - list_for_each_entry_safe(index, tmp, ®istry, head) { - if (!rcu_old_gp_ongoing(&index->ctr)) - list_move(&index->head, &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 (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 { if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) wait_gp(); else - cpu_relax(); + caa_cpu_relax(); } #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 (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 { @@ -273,20 +302,46 @@ void update_counter_and_wait(void) wait_loops = 0; break; /* only escape switch */ default: - cpu_relax(); + caa_cpu_relax(); } } #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ } - /* put back the reader list in the registry */ - 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); - if (list_empty(®istry)) + /* + * Move all waiters into our local queue. + */ + urcu_move_waiters(&waiters, &gp_waiters); + + if (cds_list_empty(®istry)) goto out; /* All threads should read qparity before accessing data structure @@ -296,29 +351,54 @@ 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 - * committing qparity update to memory. 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. + * 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 + * URCU_TLS(rcu_reader).ctr before store to rcu_gp_ctr. */ + cmm_barrier(); /* - * Adding a smp_mb() which is _not_ formally required, but makes the + * 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. */ - smp_mb(); + 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 @@ -326,6 +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); } /* @@ -342,22 +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 == 0); + 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 */ - list_add(&rcu_reader.head, ®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); - list_del(&rcu_reader.head); + cds_list_del(&URCU_TLS(rcu_reader).node); mutex_unlock(&rcu_gp_lock); } @@ -368,7 +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 @@ -376,13 +468,13 @@ void rcu_init(void) static void sigrcu_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 + * Executing this cmm_smp_mb() is the only purpose of this signal handler. + * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is * executed on. */ - smp_mb(); - _STORE_SHARED(rcu_reader.need_mb, 0); - smp_mb(); + cmm_smp_mb(); + _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); + cmm_smp_mb(); } /* @@ -406,10 +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) @@ -418,11 +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(list_empty(®istry)); + 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"