X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=src%2Furcu-defer-impl.h;h=f1fae9c0d15ce4364a44d511f2a4701febe0c4b5;hb=b47d409e2d55c101f396b47cfe4f2c909665ed2f;hp=58ca1ab2627e91ac62f452fcee9ec03196659717;hpb=4477a87021ffbfbfdb2a2084d05a084171343d36;p=urcu.git

diff --git a/src/urcu-defer-impl.h b/src/urcu-defer-impl.h
index 58ca1ab..f1fae9c 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);
@@ -265,7 +273,7 @@ void rcu_defer_barrier_thread(void)
 	_rcu_defer_barrier_thread();
 	mutex_unlock(&rcu_defer_mutex);
 }
-__attribute__((alias(urcu_stringify(rcu_defer_barrier_thread))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_barrier_thread))
 void alias_rcu_defer_barrier_thread();
 
 /*
@@ -307,7 +315,7 @@ void rcu_defer_barrier(void)
 end:
 	mutex_unlock(&rcu_defer_mutex);
 }
-__attribute__((alias(urcu_stringify(rcu_defer_barrier))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_barrier))
 void alias_rcu_defer_barrier();
 
 /*
@@ -376,7 +384,7 @@ static void _defer_rcu(void (*fct)(void *p), void *p)
 	wake_up_defer();
 }
 
-static void *thr_defer(void *args)
+static void *thr_defer(void *args __attribute__((unused)))
 {
 	for (;;) {
 		/*
@@ -401,7 +409,7 @@ void defer_rcu(void (*fct)(void *p), void *p)
 {
 	_defer_rcu(fct, p);
 }
-__attribute__((alias(urcu_stringify(defer_rcu)))) void alias_defer_rcu();
+URCU_ATTR_ALIAS(urcu_stringify(defer_rcu)) void alias_defer_rcu();
 
 static void start_defer_thread(void)
 {
@@ -450,7 +458,7 @@ int rcu_defer_register_thread(void)
 	mutex_unlock(&defer_thread_mutex);
 	return 0;
 }
-__attribute__((alias(urcu_stringify(rcu_defer_register_thread))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_register_thread))
 int alias_rcu_defer_register_thread();
 
 void rcu_defer_unregister_thread(void)
@@ -470,14 +478,14 @@ void rcu_defer_unregister_thread(void)
 		stop_defer_thread();
 	mutex_unlock(&defer_thread_mutex);
 }
-__attribute__((alias(urcu_stringify(rcu_defer_unregister_thread))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_unregister_thread))
 void alias_rcu_defer_unregister_thread();
 
 void rcu_defer_exit(void)
 {
 	assert(cds_list_empty(&registry_defer));
 }
-__attribute__((alias(urcu_stringify(rcu_defer_exit))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_exit))
 void alias_rcu_defer_exit();
 
 #endif /* _URCU_DEFER_IMPL_H */