X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=src%2Furcu-defer-impl.h;h=cbb0ca8565bfe2b52806e343f7f61d09117d6f8c;hb=8c677380d0f9241b9cd548082cf843c5111736d8;hp=d25e9b93f4dc17e8f1e6ee986ad04cdca366527f;hpb=014775106c60f02818ca755b331f887030bd440f;p=urcu.git

diff --git a/src/urcu-defer-impl.h b/src/urcu-defer-impl.h
index d25e9b9..cbb0ca8 100644
--- a/src/urcu-defer-impl.h
+++ b/src/urcu-defer-impl.h
@@ -194,17 +194,25 @@ static void wait_defer(void)
 		uatomic_set(&defer_thread_futex, 0);
 	} else {
 		cmm_smp_rmb();	/* Read queue before read futex */
-		if (uatomic_read(&defer_thread_futex) != -1)
-			return;
-		while (futex_noasync(&defer_thread_futex, FUTEX_WAIT, -1,
-				NULL, NULL, 0)) {
+		while (uatomic_read(&defer_thread_futex) == -1) {
+			if (!futex_noasync(&defer_thread_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);
@@ -401,8 +409,18 @@ void defer_rcu(void (*fct)(void *p), void *p)
 static void start_defer_thread(void)
 {
 	int ret;
+	sigset_t newmask, oldmask;
+
+	ret = sigfillset(&newmask);
+	urcu_posix_assert(!ret);
+	ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
+	urcu_posix_assert(!ret);
 
 	ret = pthread_create(&tid_defer, NULL, thr_defer, NULL);
+	if (ret)
+		urcu_die(ret);
+
+	ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 	urcu_posix_assert(!ret);
 }