X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=src%2Fworkqueue.c;h=1e0cbbab53b5088a8d7d1027f11e6493028e2469;hb=998a67fe12ae9c054f7e6ef129e51292ad426438;hp=c2c9b9c57417855d8b48f85adbcbed9c6cb6bab6;hpb=a9e31859feb8d62a3e9d8a434c3f1bd80dbe3076;p=urcu.git

diff --git a/src/workqueue.c b/src/workqueue.c
index c2c9b9c..1e0cbba 100644
--- a/src/workqueue.c
+++ b/src/workqueue.c
@@ -124,7 +124,7 @@ static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
 	return ret;
 }
 #else
-static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
+static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue __attribute__((unused)))
 {
 	return 0;
 }
@@ -132,18 +132,29 @@ static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
 
 static void futex_wait(int32_t *futex)
 {
+	int ret;
+
 	/* 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);