X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=src%2Furcu-defer-impl.h;h=603cc85fc368561efc38eb9cf1ed705fa5c97378;hb=17de0299a62acd372dd81208de6dfa79d99116cc;hp=f96553365ba4f51035f427798edd2ac4eb981f13;hpb=2f6618651c31c05ba1adbb5cdcf0d92980c38f38;p=urcu.git

diff --git a/src/urcu-defer-impl.h b/src/urcu-defer-impl.h
index f965533..603cc85 100644
--- a/src/urcu-defer-impl.h
+++ b/src/urcu-defer-impl.h
@@ -50,6 +50,7 @@
 #include <urcu/system.h>
 #include <urcu/tls-compat.h>
 #include "urcu-die.h"
+#include "urcu-utils.h"
 
 /*
  * Number of entries in the per-thread defer queue. Must be power of 2.
@@ -107,7 +108,7 @@ struct defer_queue {
 };
 
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
-#include "urcu-defer.h"
+#include <urcu/defer.h>
 
 void __attribute__((destructor)) rcu_defer_exit(void);
 
@@ -193,17 +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);
@@ -371,7 +380,7 @@ 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 (;;) {
 		/*
@@ -402,7 +411,8 @@ static void start_defer_thread(void)
 	int ret;
 
 	ret = pthread_create(&tid_defer, NULL, thr_defer, NULL);
-	assert(!ret);
+	if (ret)
+		urcu_die(ret);
 }
 
 static void stop_defer_thread(void)