X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=src%2Furcu.c;h=5f4a7d71c2fad83e414e5c32f09ff884aac13488;hp=c60307e15351241dbb0158b5d48d589852fcca65;hb=HEAD;hpb=90f72b8c054ca4e3b4b45f630549c784e26ce79a diff --git a/src/urcu.c b/src/urcu.c index c60307e..5f4a7d7 100644 --- a/src/urcu.c +++ b/src/urcu.c @@ -1,25 +1,11 @@ +// SPDX-FileCopyrightText: 2009 Mathieu Desnoyers +// SPDX-FileCopyrightText: 2009 Paul E. McKenney, IBM Corporation. +// +// SPDX-License-Identifier: LGPL-2.1-or-later + /* - * urcu.c - * * Userspace RCU library * - * Copyright (c) 2009 Mathieu Desnoyers - * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. - * - * 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. */ @@ -38,6 +24,7 @@ #include #include +#include #include #include #include @@ -99,20 +86,12 @@ int urcu_memb_has_sys_membarrier = 0; void __attribute__((constructor)) rcu_init(void); #endif -#ifdef RCU_MB +#if defined(RCU_MB) void rcu_init(void) { } #endif -#ifdef RCU_SIGNAL -static int init_done; - -void __attribute__((constructor)) rcu_init(void); - -static DEFINE_URCU_TLS(int, rcu_signal_was_blocked); -#endif - void __attribute__((destructor)) rcu_exit(void); static void urcu_call_rcu_exit(void); @@ -192,62 +171,13 @@ static void smp_mb_master(void) } #endif -#ifdef RCU_MB +#if defined(RCU_MB) static void smp_mb_master(void) { cmm_smp_mb(); } #endif -#ifdef RCU_SIGNAL -static void force_mb_all_readers(void) -{ - struct urcu_reader *index; - - /* - * 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 (cds_list_empty(®istry)) - return; - /* - * 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 cmm_smp_mc() to make sure the - * cache flush is enforced. - */ - cds_list_for_each_entry(index, ®istry, node) { - CMM_STORE_SHARED(index->need_mb, 1); - pthread_kill(index->tid, SIGRCU); - } - /* - * Wait for sighandler (and thus mb()) to execute on every thread. - * - * Note that the pthread_kill() will never be executed on systems - * that correctly deliver signals in a timely manner. However, it - * is not uncommon for kernels to have bugs that can result in - * lost or unduly delayed signals. - * - * If you are seeing the below pthread_kill() executing much at - * all, we suggest testing the underlying kernel and filing the - * relevant bug report. For Linux kernels, we recommend getting - * the Linux Test Project (LTP). - */ - cds_list_for_each_entry(index, ®istry, node) { - while (CMM_LOAD_SHARED(index->need_mb)) { - pthread_kill(index->tid, SIGRCU); - (void) poll(NULL, 0, 1); - } - } - cmm_smp_mb(); /* read ->need_mb before ending the barrier */ -} - -static void smp_mb_master(void) -{ - force_mb_all_readers(); -} -#endif /* #ifdef RCU_SIGNAL */ - /* * synchronize_rcu() waiting. Single thread. * Always called with rcu_registry lock held. Releases this lock and @@ -256,9 +186,7 @@ static void smp_mb_master(void) static void wait_gp(void) { /* - * Read reader_gp before read futex. smp_mb_master() needs to - * be called with the rcu registry lock held in RCU_SIGNAL - * flavor. + * Read reader_gp before read futex. */ smp_mb_master(); /* Temporarily unlock the registry lock. */ @@ -300,7 +228,8 @@ end: */ static void wait_for_readers(struct cds_list_head *input_readers, struct cds_list_head *cur_snap_readers, - struct cds_list_head *qsreaders) + struct cds_list_head *qsreaders, + cmm_annotate_t *group) { unsigned int wait_loops = 0; struct urcu_reader *index, *tmp; @@ -323,7 +252,7 @@ static void wait_for_readers(struct cds_list_head *input_readers, } cds_list_for_each_entry_safe(index, tmp, input_readers, node) { - switch (urcu_common_reader_state(&rcu_gp, &index->ctr)) { + switch (urcu_common_reader_state(&rcu_gp, &index->ctr, group)) { case URCU_READER_ACTIVE_CURRENT: if (cur_snap_readers) { cds_list_move(&index->node, @@ -407,6 +336,8 @@ static void wait_for_readers(struct cds_list_head *input_readers, void synchronize_rcu(void) { + cmm_annotate_define(acquire_group); + cmm_annotate_define(release_group); CDS_LIST_HEAD(cur_snap_readers); CDS_LIST_HEAD(qsreaders); DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); @@ -421,10 +352,11 @@ void synchronize_rcu(void) * 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. */ + /* + * Not first in queue: will be awakened by another thread. + * Implies a memory barrier after grace period. + */ urcu_adaptative_busy_wait(&wait); - /* Order following memory accesses after grace period. */ - cmm_smp_mb(); return; } /* We won't need to wake ourself up */ @@ -449,13 +381,14 @@ void synchronize_rcu(void) */ /* Write new ptr before changing the qparity */ smp_mb_master(); + cmm_annotate_group_mb_release(&release_group); /* * Wait for readers to observe original parity or be quiescent. * wait_for_readers() can release and grab again rcu_registry_lock * internally. */ - wait_for_readers(®istry, &cur_snap_readers, &qsreaders); + wait_for_readers(®istry, &cur_snap_readers, &qsreaders, &acquire_group); /* * Must finish waiting for quiescent state for original parity before @@ -474,7 +407,8 @@ void synchronize_rcu(void) cmm_smp_mb(); /* Switch parity: 0 -> 1, 1 -> 0 */ - CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ URCU_GP_CTR_PHASE); + cmm_annotate_group_mem_release(&release_group, &rcu_gp.ctr); + uatomic_store(&rcu_gp.ctr, rcu_gp.ctr ^ URCU_GP_CTR_PHASE, CMM_RELAXED); /* * Must commit rcu_gp.ctr update to memory before waiting for quiescent @@ -497,7 +431,7 @@ void synchronize_rcu(void) * wait_for_readers() can release and grab again rcu_registry_lock * internally. */ - wait_for_readers(&cur_snap_readers, NULL, &qsreaders); + wait_for_readers(&cur_snap_readers, NULL, &qsreaders, &acquire_group); /* * Put quiescent reader list back into registry. @@ -510,6 +444,7 @@ void synchronize_rcu(void) * iterates on reader threads. */ smp_mb_master(); + cmm_annotate_group_mb_acquire(&acquire_group); out: mutex_unlock(&rcu_registry_lock); mutex_unlock(&rcu_gp_lock); @@ -541,52 +476,8 @@ int rcu_read_ongoing(void) return _rcu_read_ongoing(); } -#ifdef RCU_SIGNAL -/* - * Make sure the signal used by the urcu-signal flavor is unblocked - * while the thread is registered. - */ -static -void urcu_signal_unblock(void) -{ - sigset_t mask, oldmask; - int ret; - - ret = sigemptyset(&mask); - urcu_posix_assert(!ret); - ret = sigaddset(&mask, SIGRCU); - urcu_posix_assert(!ret); - ret = pthread_sigmask(SIG_UNBLOCK, &mask, &oldmask); - urcu_posix_assert(!ret); - URCU_TLS(rcu_signal_was_blocked) = sigismember(&oldmask, SIGRCU); -} - -static -void urcu_signal_restore(void) -{ - sigset_t mask; - int ret; - - if (!URCU_TLS(rcu_signal_was_blocked)) - return; - ret = sigemptyset(&mask); - urcu_posix_assert(!ret); - ret = sigaddset(&mask, SIGRCU); - urcu_posix_assert(!ret); - ret = pthread_sigmask(SIG_BLOCK, &mask, NULL); - urcu_posix_assert(!ret); -} -#else -static -void urcu_signal_unblock(void) { } -static -void urcu_signal_restore(void) { } -#endif - void rcu_register_thread(void) { - urcu_signal_unblock(); - URCU_TLS(rcu_reader).tid = pthread_self(); urcu_posix_assert(URCU_TLS(rcu_reader).need_mb == 0); urcu_posix_assert(!(URCU_TLS(rcu_reader).ctr & URCU_GP_CTR_NEST_MASK)); @@ -606,8 +497,6 @@ void rcu_unregister_thread(void) URCU_TLS(rcu_reader).registered = 0; cds_list_del(&URCU_TLS(rcu_reader).node); mutex_unlock(&rcu_registry_lock); - - urcu_signal_restore(); } #ifdef RCU_MEMBARRIER @@ -658,57 +547,6 @@ void rcu_init(void) } #endif -#ifdef RCU_SIGNAL -static void sigrcu_handler(int signo __attribute__((unused)), - siginfo_t *siginfo __attribute__((unused)), - void *context __attribute__((unused))) -{ - /* - * 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. - */ - cmm_smp_mb(); - _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); - cmm_smp_mb(); -} - -/* - * rcu_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 rcu_registry_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 rcu_init(void) -{ - struct sigaction act; - int ret; - - if (init_done) - return; - init_done = 1; - - act.sa_sigaction = sigrcu_handler; - act.sa_flags = SA_SIGINFO | SA_RESTART; - sigemptyset(&act.sa_mask); - ret = sigaction(SIGRCU, &act, NULL); - if (ret) - urcu_die(errno); -} - -/* - * Don't unregister the SIGRCU signal handler anymore, because - * call_rcu threads could still be using it shortly before the - * application exits. - * Assertion disabled because call_rcu threads are now rcu - * readers, and left running at exit. - * urcu_posix_assert(cds_list_empty(®istry)); - */ - -#endif /* #ifdef RCU_SIGNAL */ - void rcu_exit(void) { urcu_call_rcu_exit();