X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fworkqueue.c;h=a28d09dd8b6321a43147b6097d7434f7db7fe02f;hb=acdb82a20ba20467b89c67aa44ca03da610513a9;hp=e5931b5e74bfee68c3efd1ff61b53e9bc68af23f;hpb=014775106c60f02818ca755b331f887030bd440f;p=userspace-rcu.git

diff --git a/src/workqueue.c b/src/workqueue.c
index e5931b5..a28d09d 100644
--- a/src/workqueue.c
+++ b/src/workqueue.c
@@ -1,24 +1,10 @@
+// SPDX-FileCopyrightText: 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+// SPDX-FileCopyrightText: 2017 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
 /*
- * workqueue.c
- *
  * Userspace RCU library - Userspace workqeues
- *
- * Copyright (c) 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
- * Copyright (c) 2017 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * 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
  */
 
 #define _LGPL_SOURCE
@@ -131,16 +117,25 @@ static void futex_wait(int32_t *futex)
 {
 	/* Read condition before read futex */
 	cmm_smp_mb();
-	if (uatomic_read(futex) != -1)
-		return;
-	while (futex_async(futex, FUTEX_WAIT, -1, NULL, NULL, 0)) {
+	while (uatomic_read(futex) == -1) {
+		if (!futex_async(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);
@@ -275,6 +270,7 @@ struct urcu_workqueue *urcu_workqueue_create(unsigned long flags,
 {
 	struct urcu_workqueue *workqueue;
 	int ret;
+	sigset_t newmask, oldmask;
 
 	workqueue = malloc(sizeof(*workqueue));
 	if (workqueue == NULL)
@@ -295,10 +291,20 @@ struct urcu_workqueue *urcu_workqueue_create(unsigned long flags,
 	workqueue->cpu_affinity = cpu_affinity;
 	workqueue->loop_count = 0;
 	cmm_smp_mb();  /* Structure initialized before pointer is planted. */
+
+	ret = sigfillset(&newmask);
+	urcu_posix_assert(!ret);
+	ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
+	urcu_posix_assert(!ret);
+
 	ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
 	if (ret) {
 		urcu_die(ret);
 	}
+
+	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
+	urcu_posix_assert(!ret);
+
 	return workqueue;
 }
 
@@ -455,13 +461,23 @@ void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue)
 void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue)
 {
 	int ret;
+	sigset_t newmask, oldmask;
 
 	/* Clear workqueue state from parent. */
 	workqueue->flags &= ~URCU_WORKQUEUE_PAUSED;
 	workqueue->flags &= ~URCU_WORKQUEUE_PAUSE;
 	workqueue->tid = 0;
+
+	ret = sigfillset(&newmask);
+	urcu_posix_assert(!ret);
+	ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
+	urcu_posix_assert(!ret);
+
 	ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
 	if (ret) {
 		urcu_die(ret);
 	}
+
+	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
+	urcu_posix_assert(!ret);
 }