X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=src%2Furcu-qsbr.c;h=a3382857a7f358ab2f6bd548df6504c35e8bbadf;hb=4974ad5f21d2cb17d313504f8d1252738526d588;hp=e934d3b57f7681225e1577089fdd589b17a6ad33;hpb=f99c6e92aaa1582e6cd19d93d44d91d968f39aa7;p=urcu.git

diff --git a/src/urcu-qsbr.c b/src/urcu-qsbr.c
index e934d3b..a338285 100644
--- a/src/urcu-qsbr.c
+++ b/src/urcu-qsbr.c
@@ -28,13 +28,13 @@
 #include <stdio.h>
 #include <pthread.h>
 #include <signal.h>
-#include <assert.h>
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
 #include <errno.h>
 #include <poll.h>
 
+#include <urcu/assert.h>
 #include <urcu/wfcqueue.h>
 #include <urcu/map/urcu-qsbr.h>
 #define BUILD_QSBR_LIB
@@ -123,17 +123,25 @@ static void wait_gp(void)
 {
 	/* Read reader_gp before read futex */
 	cmm_smp_rmb();
-	if (uatomic_read(&urcu_qsbr_gp.futex) != -1)
-		return;
-	while (futex_noasync(&urcu_qsbr_gp.futex, FUTEX_WAIT, -1,
-			NULL, NULL, 0)) {
+	while (uatomic_read(&urcu_qsbr_gp.futex) == -1) {
+		if (!futex_noasync(&urcu_qsbr_gp.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);
@@ -470,10 +478,10 @@ void urcu_qsbr_thread_online(void)
 void urcu_qsbr_register_thread(void)
 {
 	URCU_TLS(urcu_qsbr_reader).tid = pthread_self();
-	assert(URCU_TLS(urcu_qsbr_reader).ctr == 0);
+	urcu_posix_assert(URCU_TLS(urcu_qsbr_reader).ctr == 0);
 
 	mutex_lock(&rcu_registry_lock);
-	assert(!URCU_TLS(urcu_qsbr_reader).registered);
+	urcu_posix_assert(!URCU_TLS(urcu_qsbr_reader).registered);
 	URCU_TLS(urcu_qsbr_reader).registered = 1;
 	cds_list_add(&URCU_TLS(urcu_qsbr_reader).node, &registry);
 	mutex_unlock(&rcu_registry_lock);
@@ -487,7 +495,7 @@ void urcu_qsbr_unregister_thread(void)
 	 * with a waiting writer.
 	 */
 	_urcu_qsbr_thread_offline();
-	assert(URCU_TLS(urcu_qsbr_reader).registered);
+	urcu_posix_assert(URCU_TLS(urcu_qsbr_reader).registered);
 	URCU_TLS(urcu_qsbr_reader).registered = 0;
 	mutex_lock(&rcu_registry_lock);
 	cds_list_del(&URCU_TLS(urcu_qsbr_reader).node);
@@ -499,7 +507,7 @@ void urcu_qsbr_exit(void)
 	/*
 	 * Assertion disabled because call_rcu threads are now rcu
 	 * readers, and left running at exit.
-	 * assert(cds_list_empty(&registry));
+	 * urcu_posix_assert(cds_list_empty(&registry));
 	 */
 }