X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=src%2Fworkqueue.c;h=1e0cbbab53b5088a8d7d1027f11e6493028e2469;hb=998a67fe12ae9c054f7e6ef129e51292ad426438;hp=6707ffe3b45e2c2226d99c3b163d4e1c820028aa;hpb=d25f25df027b158726f8a361e52f0e3a7529d5eb;p=urcu.git

diff --git a/src/workqueue.c b/src/workqueue.c
index 6707ffe..1e0cbba 100644
--- a/src/workqueue.c
+++ b/src/workqueue.c
@@ -36,12 +36,12 @@
 #include <sched.h>
 
 #include "compat-getcpu.h"
-#include "urcu/wfcqueue.h"
-#include "urcu-pointer.h"
-#include "urcu/list.h"
-#include "urcu/futex.h"
-#include "urcu/tls-compat.h"
-#include "urcu/ref.h"
+#include <urcu/wfcqueue.h>
+#include <urcu/pointer.h>
+#include <urcu/list.h>
+#include <urcu/futex.h>
+#include <urcu/tls-compat.h>
+#include <urcu/ref.h>
 #include "urcu-die.h"
 
 #include "workqueue.h"
@@ -92,7 +92,7 @@ struct urcu_workqueue_completion_work {
  * Losing affinity can be caused by CPU hotunplug/hotplug, or by
  * cpuset(7).
  */
-#if HAVE_SCHED_SETAFFINITY
+#ifdef HAVE_SCHED_SETAFFINITY
 static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
 {
 	cpu_set_t mask;
@@ -124,7 +124,7 @@ static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
 	return ret;
 }
 #else
-static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
+static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue __attribute__((unused)))
 {
 	return 0;
 }
@@ -132,18 +132,29 @@ static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
 
 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);
@@ -238,18 +249,18 @@ static void *workqueue_thread(void *arg)
 			if (cds_wfcq_empty(&workqueue->cbs_head,
 					&workqueue->cbs_tail)) {
 				futex_wait(&workqueue->futex);
-				(void) poll(NULL, 0, 10);
 				uatomic_dec(&workqueue->futex);
 				/*
 				 * Decrement futex before reading
 				 * urcu_work list.
 				 */
 				cmm_smp_mb();
-			} else {
-				(void) poll(NULL, 0, 10);
 			}
 		} else {
-			(void) poll(NULL, 0, 10);
+			if (cds_wfcq_empty(&workqueue->cbs_head,
+					&workqueue->cbs_tail)) {
+				(void) poll(NULL, 0, 10);
+			}
 		}
 		if (workqueue->worker_after_wake_up_fct)
 			workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv);