X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-qsbr.c;fp=urcu-qsbr.c;h=0000000000000000000000000000000000000000;hp=af82fb7e6d3d6bbe3d6ef199c5c9d23ce9253163;hb=6893800a4d1cc14dff0395ddcd660a5138db183d;hpb=a59f39055b5ecb77b68cf78b9839aa9e8e4ec332 diff --git a/urcu-qsbr.c b/urcu-qsbr.c deleted file mode 100644 index af82fb7..0000000 --- a/urcu-qsbr.c +++ /dev/null @@ -1,504 +0,0 @@ -/* - * urcu-qsbr.c - * - * Userspace RCU QSBR 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. - */ - -#define _GNU_SOURCE -#define _LGPL_SOURCE -#include -#include -#include -#include -#include -#include -#include -#include -#include - -#include "urcu/wfcqueue.h" -#include "urcu/map/urcu-qsbr.h" -#define BUILD_QSBR_LIB -#include "urcu/static/urcu-qsbr.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-qsbr.h" -#define _LGPL_SOURCE - -void __attribute__((destructor)) rcu_exit(void); - -/* - * rcu_gp_lock ensures mutual exclusion between threads calling - * synchronize_rcu(). - */ -static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; -/* - * rcu_registry_lock ensures mutual exclusion between threads - * registering and unregistering themselves to/from the registry, and - * with threads reading that registry from synchronize_rcu(). However, - * this lock is not held all the way through the completion of awaiting - * for the grace period. It is sporadically released between iterations - * on the registry. - * rcu_registry_lock may nest inside rcu_gp_lock. - */ -static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; -struct rcu_gp rcu_gp = { .ctr = RCU_GP_ONLINE }; - -/* - * Active attempts to check for reader Q.S. before calling futex(). - */ -#define RCU_QS_ACTIVE_ATTEMPTS 100 - -/* - * Written to only by each individual reader. Read by both the reader and the - * writers. - */ -DEFINE_URCU_TLS(struct rcu_reader, rcu_reader); - -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) -{ - int ret; - -#ifndef DISTRUST_SIGNALS_EXTREME - ret = pthread_mutex_lock(mutex); - if (ret) - urcu_die(ret); -#else /* #ifndef DISTRUST_SIGNALS_EXTREME */ - while ((ret = pthread_mutex_trylock(mutex)) != 0) { - if (ret != EBUSY && ret != EINTR) - urcu_die(ret); - poll(NULL,0,10); - } -#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ -} - -static void mutex_unlock(pthread_mutex_t *mutex) -{ - int ret; - - ret = pthread_mutex_unlock(mutex); - if (ret) - urcu_die(ret); -} - -/* - * synchronize_rcu() waiting. Single thread. - */ -static void wait_gp(void) -{ - /* Read reader_gp before read futex */ - cmm_smp_rmb(); - if (uatomic_read(&rcu_gp.futex) != -1) - return; - while (futex_noasync(&rcu_gp.futex, FUTEX_WAIT, -1, - NULL, NULL, 0)) { - switch (errno) { - case EWOULDBLOCK: - /* Value already changed. */ - return; - case EINTR: - /* Retry if interrupted by signal. */ - break; /* Get out of switch. */ - default: - /* Unexpected error. */ - urcu_die(errno); - } - } -} - -/* - * Always called with rcu_registry lock held. Releases this lock between - * iterations and grabs it again. Holds the lock when it returns. - */ -static void wait_for_readers(struct cds_list_head *input_readers, - struct cds_list_head *cur_snap_readers, - struct cds_list_head *qsreaders) -{ - unsigned int wait_loops = 0; - struct rcu_reader *index, *tmp; - - /* - * Wait for each thread URCU_TLS(rcu_reader).ctr to either - * indicate quiescence (offline), or for them to observe the - * current rcu_gp.ctr value. - */ - for (;;) { - if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) - wait_loops++; - if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { - uatomic_set(&rcu_gp.futex, -1); - /* - * Write futex before write waiting (the other side - * reads them in the opposite order). - */ - cmm_smp_wmb(); - cds_list_for_each_entry(index, input_readers, node) { - _CMM_STORE_SHARED(index->waiting, 1); - } - /* Write futex before read reader_gp */ - cmm_smp_mb(); - } - 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(input_readers)) { - if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { - /* Read reader_gp before write futex */ - cmm_smp_mb(); - uatomic_set(&rcu_gp.futex, 0); - } - break; - } else { - /* Temporarily unlock the registry lock. */ - mutex_unlock(&rcu_registry_lock); - if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { - wait_gp(); - } else { -#ifndef HAS_INCOHERENT_CACHES - caa_cpu_relax(); -#else /* #ifndef HAS_INCOHERENT_CACHES */ - cmm_smp_mb(); -#endif /* #else #ifndef HAS_INCOHERENT_CACHES */ - } - /* Re-lock the registry lock before the next loop. */ - mutex_lock(&rcu_registry_lock); - } - } -} - -/* - * Using a two-subphases algorithm for architectures with smaller than 64-bit - * long-size to ensure we do not encounter an overflow bug. - */ - -#if (CAA_BITS_PER_LONG < 64) -void synchronize_rcu(void) -{ - CDS_LIST_HEAD(cur_snap_readers); - CDS_LIST_HEAD(qsreaders); - unsigned long was_online; - DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); - struct urcu_waiters waiters; - - was_online = rcu_read_ongoing(); - - /* All threads should read qparity before accessing data structure - * where new ptr points to. In the "then" case, rcu_thread_offline - * includes a memory barrier. - * - * Mark the writer thread offline to make sure we don't wait for - * our own quiescent state. This allows using synchronize_rcu() - * in threads registered as readers. - */ - if (was_online) - rcu_thread_offline(); - else - cmm_smp_mb(); - - /* - * 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. - */ - if (urcu_wait_add(&gp_waiters, &wait) != 0) { - /* Not first in queue: will be awakened by another thread. */ - urcu_adaptative_busy_wait(&wait); - goto gp_end; - } - /* We won't need to wake ourself up */ - urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); - - mutex_lock(&rcu_gp_lock); - - /* - * Move all waiters into our local queue. - */ - urcu_move_waiters(&waiters, &gp_waiters); - - mutex_lock(&rcu_registry_lock); - - if (cds_list_empty(®istry)) - goto out; - - /* - * Wait for readers to observe original parity or be quiescent. - * wait_for_readers() can release and grab again rcu_registry_lock - * interally. - */ - wait_for_readers(®istry, &cur_snap_readers, &qsreaders); - - /* - * 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 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); - - /* - * 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 URCU_TLS(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. - */ - cmm_smp_mb(); - - /* - * Wait for readers to observe new parity or be quiescent. - * wait_for_readers() can release and grab again rcu_registry_lock - * interally. - */ - wait_for_readers(&cur_snap_readers, NULL, &qsreaders); - - /* - * Put quiescent reader list back into registry. - */ - cds_list_splice(&qsreaders, ®istry); -out: - mutex_unlock(&rcu_registry_lock); - mutex_unlock(&rcu_gp_lock); - urcu_wake_all_waiters(&waiters); -gp_end: - /* - * Finish waiting for reader threads before letting the old ptr being - * freed. - */ - if (was_online) - rcu_thread_online(); - else - cmm_smp_mb(); -} -#else /* !(CAA_BITS_PER_LONG < 64) */ -void synchronize_rcu(void) -{ - CDS_LIST_HEAD(qsreaders); - unsigned long was_online; - DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); - struct urcu_waiters waiters; - - was_online = rcu_read_ongoing(); - - /* - * Mark the writer thread offline to make sure we don't wait for - * our own quiescent state. This allows using synchronize_rcu() - * in threads registered as readers. - */ - if (was_online) - rcu_thread_offline(); - else - cmm_smp_mb(); - - /* - * 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. - */ - if (urcu_wait_add(&gp_waiters, &wait) != 0) { - /* Not first in queue: will be awakened by another thread. */ - urcu_adaptative_busy_wait(&wait); - goto gp_end; - } - /* We won't need to wake ourself up */ - urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); - - mutex_lock(&rcu_gp_lock); - - /* - * Move all waiters into our local queue. - */ - urcu_move_waiters(&waiters, &gp_waiters); - - mutex_lock(&rcu_registry_lock); - - if (cds_list_empty(®istry)) - goto out; - - /* Increment current G.P. */ - CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr + RCU_GP_CTR); - - /* - * 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 URCU_TLS(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. - */ - cmm_smp_mb(); - - /* - * Wait for readers to observe new count of be quiescent. - * wait_for_readers() can release and grab again rcu_registry_lock - * interally. - */ - wait_for_readers(®istry, NULL, &qsreaders); - - /* - * Put quiescent reader list back into registry. - */ - cds_list_splice(&qsreaders, ®istry); -out: - mutex_unlock(&rcu_registry_lock); - mutex_unlock(&rcu_gp_lock); - urcu_wake_all_waiters(&waiters); -gp_end: - if (was_online) - rcu_thread_online(); - else - cmm_smp_mb(); -} -#endif /* !(CAA_BITS_PER_LONG < 64) */ - -/* - * 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(); -} - -int rcu_read_ongoing(void) -{ - return _rcu_read_ongoing(); -} - -void rcu_quiescent_state(void) -{ - _rcu_quiescent_state(); -} - -void rcu_thread_offline(void) -{ - _rcu_thread_offline(); -} - -void rcu_thread_online(void) -{ - _rcu_thread_online(); -} - -void rcu_register_thread(void) -{ - URCU_TLS(rcu_reader).tid = pthread_self(); - assert(URCU_TLS(rcu_reader).ctr == 0); - - mutex_lock(&rcu_registry_lock); - assert(!URCU_TLS(rcu_reader).registered); - URCU_TLS(rcu_reader).registered = 1; - cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); - mutex_unlock(&rcu_registry_lock); - _rcu_thread_online(); -} - -void rcu_unregister_thread(void) -{ - /* - * We have to make the thread offline otherwise we end up dealocking - * with a waiting writer. - */ - _rcu_thread_offline(); - assert(URCU_TLS(rcu_reader).registered); - URCU_TLS(rcu_reader).registered = 0; - mutex_lock(&rcu_registry_lock); - cds_list_del(&URCU_TLS(rcu_reader).node); - mutex_unlock(&rcu_registry_lock); -} - -void rcu_exit(void) -{ - /* - * Assertion disabled because call_rcu threads are now rcu - * readers, and left running at exit. - * assert(cds_list_empty(®istry)); - */ -} - -DEFINE_RCU_FLAVOR(rcu_flavor); - -#include "urcu-call-rcu-impl.h" -#include "urcu-defer-impl.h"