X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=urcu.c;h=c210a1341ade8a189752417249bb47bca73a03aa;hp=38abf7d6a92e045bb2aabbc306a4b7006ed108f8;hb=538d7df5086144837beb7a9c1e2a94eb637b9904;hpb=09a9f9867bf0c7fd793f46f1e639ad2042175721 diff --git a/urcu.c b/urcu.c index 38abf7d..c210a13 100644 --- a/urcu.c +++ b/urcu.c @@ -3,9 +3,24 @@ * * Userspace RCU library * - * Copyright February 2009 - Mathieu Desnoyers + * Copyright (c) 2009 Mathieu Desnoyers + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. * - * Distributed under GPLv2 + * 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. */ #include @@ -15,9 +30,23 @@ #include #include #include +#include +#include "urcu-static.h" +/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ #include "urcu.h" +#ifndef CONFIG_URCU_AVOID_SIGNALS +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; /* @@ -98,18 +127,20 @@ static void switch_next_urcu_qparity(void) STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT); } -#ifdef DEBUG_FULL_MB +#ifdef CONFIG_URCU_AVOID_SIGNALS +#ifdef HAS_INCOHERENT_CACHES static void force_mb_single_thread(struct reader_registry *index) { smp_mb(); } +#endif /* #ifdef HAS_INCOHERENT_CACHES */ static void force_mb_all_threads(void) { smp_mb(); } -#else - +#else /* #ifdef CONFIG_URCU_AVOID_SIGNALS */ +#ifdef HAS_INCOHERENT_CACHES static void force_mb_single_thread(struct reader_registry *index) { assert(registry); @@ -132,6 +163,7 @@ static void force_mb_single_thread(struct reader_registry *index) } smp_mb(); /* read ->need_mb before ending the barrier */ } +#endif /* #ifdef HAS_INCOHERENT_CACHES */ static void force_mb_all_threads(void) { @@ -174,7 +206,7 @@ static void force_mb_all_threads(void) } smp_mb(); /* read ->need_mb before ending the barrier */ } -#endif +#endif /* #else #ifdef CONFIG_URCU_AVOID_SIGNALS */ void wait_for_quiescent_state(void) { @@ -186,6 +218,10 @@ void wait_for_quiescent_state(void) * Wait for each thread urcu_active_readers count to become 0. */ for (index = registry; index < registry + num_readers; index++) { +#ifndef HAS_INCOHERENT_CACHES + while (rcu_old_gp_ongoing(index->urcu_active_readers)) + cpu_relax(); +#else /* #ifndef HAS_INCOHERENT_CACHES */ int wait_loops = 0; /* * BUSY-LOOP. Force the reader thread to commit its @@ -199,6 +235,7 @@ void wait_for_quiescent_state(void) cpu_relax(); } } +#endif /* #else #ifndef HAS_INCOHERENT_CACHES */ } } @@ -222,6 +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. */ @@ -235,6 +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 */ /* @@ -245,6 +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. */ @@ -258,7 +316,47 @@ void synchronize_rcu(void) internal_urcu_unlock(); } -void urcu_add_reader(pthread_t id) +/* + * library wrappers to be used by non-LGPL compatible source code. + */ + +void rcu_read_lock(void) +{ + _rcu_read_lock(); +} + +void rcu_read_unlock(void) +{ + _rcu_read_unlock(); +} + +void *rcu_dereference(void *p) +{ + return _rcu_dereference(p); +} + +void *rcu_assign_pointer_sym(void **p, void *v) +{ + wmb(); + return STORE_SHARED(p, v); +} + +void *rcu_xchg_pointer_sym(void **p, void *v) +{ + wmb(); + return xchg(p, v); +} + +void *rcu_publish_content_sym(void **p, void *v) +{ + void *oldptr; + + oldptr = _rcu_xchg_pointer(p, v); + synchronize_rcu(); + return oldptr; +} + +static void rcu_add_reader(pthread_t id) { struct reader_registry *oldarray; @@ -288,7 +386,7 @@ void urcu_add_reader(pthread_t id) * Never shrink (implementation limitation). * This is O(nb threads). Eventually use a hash table. */ -void urcu_remove_reader(pthread_t id) +static void rcu_remove_reader(pthread_t id) { struct reader_registry *index; @@ -307,22 +405,23 @@ void urcu_remove_reader(pthread_t id) assert(0); } -void urcu_register_thread(void) +void rcu_register_thread(void) { internal_urcu_lock(); - urcu_add_reader(pthread_self()); + urcu_init(); /* In case gcc does not support constructor attribute */ + rcu_add_reader(pthread_self()); internal_urcu_unlock(); } -void urcu_unregister_thread(void) +void rcu_unregister_thread(void) { internal_urcu_lock(); - urcu_remove_reader(pthread_self()); + rcu_remove_reader(pthread_self()); internal_urcu_unlock(); } -#ifndef DEBUG_FULL_MB -void sigurcu_handler(int signo, siginfo_t *siginfo, void *context) +#ifndef CONFIG_URCU_AVOID_SIGNALS +static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context) { /* * Executing this smp_mb() is the only purpose of this signal handler. @@ -334,12 +433,26 @@ 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"); @@ -347,7 +460,7 @@ void __attribute__((constructor)) urcu_init(void) } } -void __attribute__((destructor)) urcu_exit(void) +void urcu_exit(void) { struct sigaction act; int ret; @@ -360,4 +473,4 @@ void __attribute__((destructor)) urcu_exit(void) assert(act.sa_sigaction == sigurcu_handler); free(registry); } -#endif +#endif /* #ifndef CONFIG_URCU_AVOID_SIGNALS */