X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=src%2Furcu-qsbr.c;h=40c0fbdb35519983186c67615f8c285a691f91d8;hp=f343f0d836f642360b4b6f3e24dbae6358e1bbf4;hb=HEAD;hpb=6fd172f599e8d798e68974a786dd930d876f182e diff --git a/src/urcu-qsbr.c b/src/urcu-qsbr.c index f343f0d..e7ee180 100644 --- a/src/urcu-qsbr.c +++ b/src/urcu-qsbr.c @@ -1,55 +1,46 @@ +// SPDX-FileCopyrightText: 2009 Mathieu Desnoyers +// SPDX-FileCopyrightText: 2009 Paul E. McKenney, IBM Corporation. +// +// SPDX-License-Identifier: LGPL-2.1-or-later + /* - * 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 URCU_NO_COMPAT_IDENTIFIERS #define _LGPL_SOURCE #include #include #include -#include #include #include #include #include #include -#include "urcu/wfcqueue.h" -#include "urcu/map/urcu-qsbr.h" +#include +#include +#include +#include #define BUILD_QSBR_LIB -#include "urcu/static/urcu-qsbr.h" -#include "urcu-pointer.h" -#include "urcu/tls-compat.h" +#include +#include +#include #include "urcu-die.h" #include "urcu-wait.h" +#include "urcu-utils.h" +#define URCU_API_MAP /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ #undef _LGPL_SOURCE -#include "urcu-qsbr.h" +#include #define _LGPL_SOURCE -void __attribute__((destructor)) rcu_exit(void); +void __attribute__((destructor)) urcu_qsbr_exit(void); +static void urcu_call_rcu_exit(void); /* * rcu_gp_lock ensures mutual exclusion between threads calling @@ -66,7 +57,7 @@ static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; * 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 }; +struct urcu_gp urcu_qsbr_gp = { .ctr = URCU_QSBR_GP_ONLINE }; /* * Active attempts to check for reader Q.S. before calling futex(). @@ -77,7 +68,7 @@ struct rcu_gp rcu_gp = { .ctr = RCU_GP_ONLINE }; * Written to only by each individual reader. Read by both the reader and the * writers. */ -DEFINE_URCU_TLS_IE(struct rcu_reader, rcu_reader); +DEFINE_URCU_TLS(struct urcu_qsbr_reader, urcu_qsbr_reader); static CDS_LIST_HEAD(registry); @@ -120,17 +111,25 @@ 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)) { + while (uatomic_read(&urcu_qsbr_gp.futex) == -1) { + if (!futex_noasync(&urcu_qsbr_gp.futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { + /* + * Prior queued wakeups queued by unrelated code + * using the same address can cause futex wait to + * return 0 even through the futex value is still + * -1 (spurious wakeups). Check the value again + * in user-space to validate whether it really + * differs from -1. + */ + continue; + } switch (errno) { - case EWOULDBLOCK: + case EAGAIN: /* Value already changed. */ return; case EINTR: /* Retry if interrupted by signal. */ - break; /* Get out of switch. */ + break; /* Get out of switch. Check again. */ default: /* Unexpected error. */ urcu_die(errno); @@ -144,21 +143,22 @@ static void wait_gp(void) */ 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 rcu_reader *index, *tmp; + struct urcu_qsbr_reader *index, *tmp; /* - * Wait for each thread URCU_TLS(rcu_reader).ctr to either + * Wait for each thread URCU_TLS(urcu_qsbr_reader).ctr to either * indicate quiescence (offline), or for them to observe the - * current rcu_gp.ctr value. + * current urcu_qsbr_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); + uatomic_set(&urcu_qsbr_gp.futex, -1); /* * Write futex before write waiting (the other side * reads them in the opposite order). @@ -171,18 +171,18 @@ static void wait_for_readers(struct cds_list_head *input_readers, 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: + switch (urcu_qsbr_reader_state(&index->ctr, group)) { + case URCU_READER_ACTIVE_CURRENT: if (cur_snap_readers) { cds_list_move(&index->node, cur_snap_readers); break; } /* Fall-through */ - case RCU_READER_INACTIVE: + case URCU_READER_INACTIVE: cds_list_move(&index->node, qsreaders); break; - case RCU_READER_ACTIVE_OLD: + case URCU_READER_ACTIVE_OLD: /* * Old snapshot. Leaving node in * input_readers will make us busy-loop @@ -196,8 +196,7 @@ static void wait_for_readers(struct cds_list_head *input_readers, 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); + uatomic_store(&urcu_qsbr_gp.futex, 0, CMM_RELEASE); } break; } else { @@ -224,15 +223,17 @@ static void wait_for_readers(struct cds_list_head *input_readers, */ #if (CAA_BITS_PER_LONG < 64) -void synchronize_rcu(void) +void urcu_qsbr_synchronize_rcu(void) { + cmm_annotate_define(acquire_group); + cmm_annotate_define(release_group); 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(); + was_online = urcu_qsbr_read_ongoing(); /* All threads should read qparity before accessing data structure * where new ptr points to. In the "then" case, rcu_thread_offline @@ -243,9 +244,10 @@ void synchronize_rcu(void) * in threads registered as readers. */ if (was_online) - rcu_thread_offline(); + urcu_qsbr_thread_offline(); else cmm_smp_mb(); + cmm_annotate_group_mb_release(&release_group); /* * Add ourself to gp_waiters queue of threads awaiting to wait @@ -275,17 +277,17 @@ void synchronize_rcu(void) /* * Wait for readers to observe original parity or be quiescent. * wait_for_readers() can release and grab again rcu_registry_lock - * interally. + * 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 committing next rcu_gp.ctr update to memory. Failure + * before committing next urcu_qsbr_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. + * compiler-order of load URCU_TLS(urcu_qsbr_reader).ctr before store + * to urcu_qsbr_gp.ctr. */ cmm_barrier(); @@ -297,14 +299,15 @@ void synchronize_rcu(void) cmm_smp_mb(); /* Switch parity: 0 -> 1, 1 -> 0 */ - CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR); + cmm_annotate_group_mem_release(&release_group, &urcu_qsbr_gp.ctr); + uatomic_store(&urcu_qsbr_gp.ctr, urcu_qsbr_gp.ctr ^ URCU_QSBR_GP_CTR, CMM_RELAXED); /* - * Must commit rcu_gp.ctr update to memory before waiting for + * Must commit urcu_qsbr_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. + * (no progress). Enforce compiler-order of store to urcu_qsbr_gp.ctr + * before load URCU_TLS(urcu_qsbr_reader).ctr. */ cmm_barrier(); @@ -318,9 +321,9 @@ void synchronize_rcu(void) /* * Wait for readers to observe new parity or be quiescent. * wait_for_readers() can release and grab again rcu_registry_lock - * interally. + * 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. @@ -335,20 +338,24 @@ gp_end: * Finish waiting for reader threads before letting the old ptr being * freed. */ + cmm_annotate_group_mb_acquire(&acquire_group); + if (was_online) - rcu_thread_online(); + urcu_qsbr_thread_online(); else cmm_smp_mb(); } #else /* !(CAA_BITS_PER_LONG < 64) */ -void synchronize_rcu(void) +void urcu_qsbr_synchronize_rcu(void) { + cmm_annotate_define(acquire_group); + cmm_annotate_define(release_group); 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(); + was_online = urcu_qsbr_read_ongoing(); /* * Mark the writer thread offline to make sure we don't wait for @@ -356,9 +363,10 @@ void synchronize_rcu(void) * in threads registered as readers. */ if (was_online) - rcu_thread_offline(); + urcu_qsbr_thread_offline(); else cmm_smp_mb(); + cmm_annotate_group_mb_release(&release_group); /* * Add ourself to gp_waiters queue of threads awaiting to wait @@ -386,14 +394,15 @@ void synchronize_rcu(void) goto out; /* Increment current G.P. */ - CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr + RCU_GP_CTR); + cmm_annotate_group_mem_release(&release_group, &urcu_qsbr_gp.ctr); + uatomic_store(&urcu_qsbr_gp.ctr, urcu_qsbr_gp.ctr + URCU_QSBR_GP_CTR, CMM_RELAXED); /* - * Must commit rcu_gp.ctr update to memory before waiting for + * Must commit urcu_qsbr_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. + * (no progress). Enforce compiler-order of store to urcu_qsbr_gp.ctr + * before load URCU_TLS(urcu_qsbr_reader).ctr. */ cmm_barrier(); @@ -407,9 +416,9 @@ void synchronize_rcu(void) /* * Wait for readers to observe new count of be quiescent. * wait_for_readers() can release and grab again rcu_registry_lock - * interally. + * internally. */ - wait_for_readers(®istry, NULL, &qsreaders); + wait_for_readers(®istry, NULL, &qsreaders, &acquire_group); /* * Put quiescent reader list back into registry. @@ -421,9 +430,11 @@ out: urcu_wake_all_waiters(&waiters); gp_end: if (was_online) - rcu_thread_online(); + urcu_qsbr_thread_online(); else cmm_smp_mb(); + + cmm_annotate_group_mb_acquire(&acquire_group); } #endif /* !(CAA_BITS_PER_LONG < 64) */ @@ -431,73 +442,78 @@ gp_end: * library wrappers to be used by non-LGPL compatible source code. */ -void rcu_read_lock(void) +void urcu_qsbr_read_lock(void) { - _rcu_read_lock(); + _urcu_qsbr_read_lock(); } -void rcu_read_unlock(void) +void urcu_qsbr_read_unlock(void) { - _rcu_read_unlock(); + _urcu_qsbr_read_unlock(); } -int rcu_read_ongoing(void) +int urcu_qsbr_read_ongoing(void) { - return _rcu_read_ongoing(); + return _urcu_qsbr_read_ongoing(); } +void rcu_read_ongoing_qsbr(); -void rcu_quiescent_state(void) +void urcu_qsbr_quiescent_state(void) { - _rcu_quiescent_state(); + _urcu_qsbr_quiescent_state(); } +void rcu_quiescent_state_qsbr(); -void rcu_thread_offline(void) +void urcu_qsbr_thread_offline(void) { - _rcu_thread_offline(); + _urcu_qsbr_thread_offline(); } +void rcu_thread_offline_qsbr(); -void rcu_thread_online(void) +void urcu_qsbr_thread_online(void) { - _rcu_thread_online(); + _urcu_qsbr_thread_online(); } -void rcu_register_thread(void) +void urcu_qsbr_register_thread(void) { - URCU_TLS(rcu_reader).tid = pthread_self(); - assert(URCU_TLS(rcu_reader).ctr == 0); + URCU_TLS(urcu_qsbr_reader).tid = pthread_self(); + urcu_posix_assert(URCU_TLS(urcu_qsbr_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); + urcu_posix_assert(!URCU_TLS(urcu_qsbr_reader).registered); + URCU_TLS(urcu_qsbr_reader).registered = 1; + cds_list_add(&URCU_TLS(urcu_qsbr_reader).node, ®istry); mutex_unlock(&rcu_registry_lock); - _rcu_thread_online(); + _urcu_qsbr_thread_online(); } -void rcu_unregister_thread(void) +void urcu_qsbr_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; + _urcu_qsbr_thread_offline(); + urcu_posix_assert(URCU_TLS(urcu_qsbr_reader).registered); + URCU_TLS(urcu_qsbr_reader).registered = 0; mutex_lock(&rcu_registry_lock); - cds_list_del(&URCU_TLS(rcu_reader).node); + cds_list_del(&URCU_TLS(urcu_qsbr_reader).node); mutex_unlock(&rcu_registry_lock); } -void rcu_exit(void) +void urcu_qsbr_exit(void) { /* * Assertion disabled because call_rcu threads are now rcu * readers, and left running at exit. - * assert(cds_list_empty(®istry)); + * urcu_posix_assert(cds_list_empty(®istry)); */ + urcu_call_rcu_exit(); } DEFINE_RCU_FLAVOR(rcu_flavor); #include "urcu-call-rcu-impl.h" #include "urcu-defer-impl.h" +#include "urcu-poll-impl.h"