X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=07537efbc55c90943b49f1a240aab5935fc55bc7;hp=7ab87c4e4f00fb61ef3a8931494754d7bfcf0188;hb=ed868fa15f8c5511a1c32d1779f6fe37375c7137;hpb=121a5d44c8cc7197116df73854cb94c6cfbad0b0 diff --git a/urcu.c b/urcu.c index 7ab87c4..07537ef 100644 --- a/urcu.c +++ b/urcu.c @@ -3,9 +3,22 @@ * * Userspace RCU library * - * Copyright February 2009 - Mathieu Desnoyers + * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. * - * Distributed under LGPLv2.1 + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * * IBM's contributions to this file may be relicensed under LGPLv2 or later. */ @@ -23,12 +36,23 @@ /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ #include "urcu.h" +#ifndef URCU_MB +void __attribute__((constructor)) urcu_init(void); +void __attribute__((destructor)) urcu_exit(void); +#else +void urcu_init(void) +{ +} +#endif + +int init_done; + pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER; /* * Global grace period counter. * Contains the current RCU_GP_CTR_BIT. - * Also has a RCU_GP_CTR_BIT of 1, to accelerate the reader fast path. + * 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 urcu_gp_ctr = RCU_GP_COUNT; @@ -103,7 +127,7 @@ static void switch_next_urcu_qparity(void) STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT); } -#ifdef DEBUG_FULL_MB +#ifdef URCU_MB #ifdef HAS_INCOHERENT_CACHES static void force_mb_single_thread(struct reader_registry *index) { @@ -115,7 +139,7 @@ static void force_mb_all_threads(void) { smp_mb(); } -#else /* #ifdef DEBUG_FULL_MB */ +#else /* #ifdef URCU_MB */ #ifdef HAS_INCOHERENT_CACHES static void force_mb_single_thread(struct reader_registry *index) { @@ -182,7 +206,7 @@ static void force_mb_all_threads(void) } smp_mb(); /* read ->need_mb before ending the barrier */ } -#endif /* #else #ifdef DEBUG_FULL_MB */ +#endif /* #else #ifdef URCU_MB */ void wait_for_quiescent_state(void) { @@ -235,6 +259,13 @@ void synchronize_rcu(void) * 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. */ @@ -248,6 +279,13 @@ void synchronize_rcu(void) * 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(); + switch_next_urcu_qparity(); /* 1 -> 0 */ /* @@ -258,6 +296,13 @@ void synchronize_rcu(void) * 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. */ @@ -363,6 +408,7 @@ static void rcu_remove_reader(pthread_t id) void rcu_register_thread(void) { internal_urcu_lock(); + urcu_init(); /* In case gcc does not support constructor attribute */ rcu_add_reader(pthread_self()); internal_urcu_unlock(); } @@ -374,7 +420,7 @@ void rcu_unregister_thread(void) internal_urcu_unlock(); } -#ifndef DEBUG_FULL_MB +#ifndef URCU_MB static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context) { /* @@ -387,12 +433,26 @@ static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context) smp_mb(); } -void __attribute__((constructor)) urcu_init(void) +/* + * urcu_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_urcu_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 urcu_init(void) { struct sigaction act; int ret; + if (init_done) + return; + init_done = 1; + act.sa_sigaction = sigurcu_handler; + act.sa_flags = SA_SIGINFO | SA_RESTART; + sigemptyset(&act.sa_mask); ret = sigaction(SIGURCU, &act, NULL); if (ret) { perror("Error in sigaction"); @@ -400,7 +460,7 @@ void __attribute__((constructor)) urcu_init(void) } } -void __attribute__((destructor)) urcu_exit(void) +void urcu_exit(void) { struct sigaction act; int ret; @@ -413,4 +473,4 @@ void __attribute__((destructor)) urcu_exit(void) assert(act.sa_sigaction == sigurcu_handler); free(registry); } -#endif /* #ifndef DEBUG_FULL_MB */ +#endif /* #ifndef URCU_MB */