X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=src%2Fworkqueue.c;fp=src%2Fworkqueue.c;h=c9f03b56fbb3ac85c58e5ef21330e03d0377d340;hp=e5931b5e74bfee68c3efd1ff61b53e9bc68af23f;hb=80c34c2de3d970eb82049798357743cfa71e8b54;hpb=59b6b14faa1ef105997fdffd9048ec56b3808ce8

diff --git a/src/workqueue.c b/src/workqueue.c
index e5931b5..c9f03b5 100644
--- a/src/workqueue.c
+++ b/src/workqueue.c
@@ -129,18 +129,29 @@ static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue __attribute_
 
 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);