uatomic/x86: Remove redundant memory barriers

[urcu.git] / src / urcu-qsbr.c

diff --git a/src/urcu-qsbr.c b/src/urcu-qsbr.c
index a3382857a7f358ab2f6bd548df6504c35e8bbadf..e7ee180a9f81119a091de2d3156203028debb2bb 100644 (file)
--- a/src/urcu-qsbr.c
+++ b/src/urcu-qsbr.c
@@ -1,25 +1,11 @@
+// SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+// 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 <mathieu.desnoyers@efficios.com>
- * 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.
  */
 
@@ -34,6 +20,7 @@
 #include <errno.h>
 #include <poll.h>
 
+#include <urcu/annotate.h>
 #include <urcu/assert.h>
 #include <urcu/wfcqueue.h>
 #include <urcu/map/urcu-qsbr.h>
@@ -53,6 +40,7 @@
 #define _LGPL_SOURCE
 
 void __attribute__((destructor)) urcu_qsbr_exit(void);
+static void urcu_call_rcu_exit(void);
 
 /*
  * rcu_gp_lock ensures mutual exclusion between threads calling
@@ -155,7 +143,8 @@ 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 urcu_qsbr_reader *index, *tmp;
@@ -182,7 +171,7 @@ 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 (urcu_qsbr_reader_state(&index->ctr)) {
+                       switch (urcu_qsbr_reader_state(&index->ctr, group)) {
                        case URCU_READER_ACTIVE_CURRENT:
                                if (cur_snap_readers) {
                                        cds_list_move(&index->node,
@@ -207,8 +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(&urcu_qsbr_gp.futex, 0);
+                               uatomic_store(&urcu_qsbr_gp.futex, 0, CMM_RELEASE);
                        }
                        break;
                } else {
@@ -237,6 +225,8 @@ static void wait_for_readers(struct cds_list_head *input_readers,
 #if (CAA_BITS_PER_LONG < 64)
 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;
@@ -257,6 +247,7 @@ void urcu_qsbr_synchronize_rcu(void)
                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
@@ -288,7 +279,7 @@ void urcu_qsbr_synchronize_rcu(void)
         * wait_for_readers() can release and grab again rcu_registry_lock
         * internally.
         */
-       wait_for_readers(&registry, &cur_snap_readers, &qsreaders);
+       wait_for_readers(&registry, &cur_snap_readers, &qsreaders, &acquire_group);
 
        /*
         * Must finish waiting for quiescent state for original parity
@@ -308,7 +299,8 @@ void urcu_qsbr_synchronize_rcu(void)
        cmm_smp_mb();
 
        /* Switch parity: 0 -> 1, 1 -> 0 */
-       CMM_STORE_SHARED(urcu_qsbr_gp.ctr, urcu_qsbr_gp.ctr ^ URCU_QSBR_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 urcu_qsbr_gp.ctr update to memory before waiting for
@@ -331,7 +323,7 @@ void urcu_qsbr_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.
@@ -346,6 +338,8 @@ gp_end:
         * Finish waiting for reader threads before letting the old ptr being
         * freed.
         */
+       cmm_annotate_group_mb_acquire(&acquire_group);
+
        if (was_online)
                urcu_qsbr_thread_online();
        else
@@ -354,6 +348,8 @@ gp_end:
 #else /* !(CAA_BITS_PER_LONG < 64) */
 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);
@@ -370,6 +366,7 @@ void urcu_qsbr_synchronize_rcu(void)
                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
@@ -397,7 +394,8 @@ void urcu_qsbr_synchronize_rcu(void)
                goto out;
 
        /* Increment current G.P. */
-       CMM_STORE_SHARED(urcu_qsbr_gp.ctr, urcu_qsbr_gp.ctr + URCU_QSBR_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 urcu_qsbr_gp.ctr update to memory before waiting for
@@ -420,7 +418,7 @@ void urcu_qsbr_synchronize_rcu(void)
         * wait_for_readers() can release and grab again rcu_registry_lock
         * internally.
         */
-       wait_for_readers(&registry, NULL, &qsreaders);
+       wait_for_readers(&registry, NULL, &qsreaders, &acquire_group);
 
        /*
         * Put quiescent reader list back into registry.
@@ -435,6 +433,8 @@ gp_end:
                urcu_qsbr_thread_online();
        else
                cmm_smp_mb();
+
+       cmm_annotate_group_mb_acquire(&acquire_group);
 }
 #endif  /* !(CAA_BITS_PER_LONG < 64) */
 
@@ -509,9 +509,11 @@ void urcu_qsbr_exit(void)
         * readers, and left running at exit.
         * urcu_posix_assert(cds_list_empty(&registry));
         */
+       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"