X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=urcu-bp.c;h=a823659f78d4ce93d82a23b95dc05216feb9c903;hp=b9c89d899ea0d744246aa369d8417d8b5a1c4cec;hb=88c3c5ba50ae3d5a847b4214840234b8f116e928;hpb=4a6d73787de534cbd7d5fc7a6b60af64de66e7ea diff --git a/urcu-bp.c b/urcu-bp.c index b9c89d8..a823659 100644 --- a/urcu-bp.c +++ b/urcu-bp.c @@ -36,7 +36,7 @@ #include #include -#include "urcu/wfqueue.h" +#include "urcu/wfcqueue.h" #include "urcu/map/urcu-bp.h" #include "urcu/static/urcu-bp.h" #include "urcu-pointer.h" @@ -105,17 +105,11 @@ void __attribute__((destructor)) rcu_bp_exit(void); static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; #ifdef DEBUG_YIELD -unsigned int yield_active; -DEFINE_URCU_TLS(unsigned int, rand_yield); +unsigned int rcu_yield_active; +DEFINE_URCU_TLS(unsigned int, rcu_rand_yield); #endif -/* - * Global grace period counter. - * Contains the current RCU_GP_CTR_PHASE. - * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. - * Written to only by writer with mutex taken. Read by both writer and readers. - */ -long rcu_gp_ctr = RCU_GP_COUNT; +struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT }; /* * Pointer to registry elements. Written to only by each individual reader. Read @@ -164,40 +158,44 @@ static void mutex_unlock(pthread_mutex_t *mutex) urcu_die(ret); } -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 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 CMM_STORE_SHARED and CMM_LOAD_SHARED. - */ - /* - * 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++; - cds_list_for_each_entry_safe(index, tmp, ®istry, node) { - if (!rcu_old_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; + } } - if (cds_list_empty(®istry)) { + if (cds_list_empty(input_readers)) { break; } else { if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) @@ -206,18 +204,18 @@ void update_counter_and_wait(void) caa_cpu_relax(); } } - /* 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); sigset_t newmask, oldmask; int ret; - ret = sigemptyset(&newmask); + ret = sigfillset(&newmask); assert(!ret); - ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); + ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); assert(!ret); mutex_lock(&rcu_gp_lock); @@ -234,9 +232,26 @@ void synchronize_rcu(void) rcu_gc_registry(); /* - * Wait for previous parity to be empty of readers. + * Wait for readers to observe original parity or be quiescent. + */ + wait_for_readers(®istry, &cur_snap_readers, &qsreaders); + + /* + * 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 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 CMM_STORE_SHARED and CMM_LOAD_SHARED. */ - update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ /* * Adding a cmm_smp_mb() which is _not_ formally required, but makes the @@ -246,9 +261,14 @@ 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 @@ -275,6 +295,11 @@ void rcu_read_unlock(void) _rcu_read_unlock(); } +int rcu_read_ongoing(void) +{ + return _rcu_read_ongoing(); +} + /* * only grow for now. */ @@ -360,9 +385,9 @@ void rcu_bp_register(void) sigset_t newmask, oldmask; int ret; - ret = sigemptyset(&newmask); + ret = sigfillset(&newmask); assert(!ret); - ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); + ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); assert(!ret); /* @@ -395,9 +420,9 @@ void rcu_bp_before_fork(void) sigset_t newmask, oldmask; int ret; - ret = sigemptyset(&newmask); + ret = sigfillset(&newmask); assert(!ret); - ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask); + ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); assert(!ret); mutex_lock(&rcu_gp_lock); saved_fork_signal_mask = oldmask;