Disable signals in URCU background threads

[urcu.git] / src / workqueue.c

diff --git a/src/workqueue.c b/src/workqueue.c
index e5931b5e74bfee68c3efd1ff61b53e9bc68af23f..1039d7297b9ce13446c4b81aee86fa217a005eab 100644 (file)
--- a/src/workqueue.c
+++ b/src/workqueue.c
@@ -131,16 +131,25 @@ static void futex_wait(int32_t *futex)
 {
        /* 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);
@@ -275,6 +284,7 @@ struct urcu_workqueue *urcu_workqueue_create(unsigned long flags,
 {
        struct urcu_workqueue *workqueue;
        int ret;
+       sigset_t newmask, oldmask;
 
        workqueue = malloc(sizeof(*workqueue));
        if (workqueue == NULL)
@@ -295,10 +305,20 @@ struct urcu_workqueue *urcu_workqueue_create(unsigned long flags,
        workqueue->cpu_affinity = cpu_affinity;
        workqueue->loop_count = 0;
        cmm_smp_mb();  /* Structure initialized before pointer is planted. */
+
+       ret = sigfillset(&newmask);
+       urcu_posix_assert(!ret);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
+       urcu_posix_assert(!ret);
+
        ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
        if (ret) {
                urcu_die(ret);
        }
+
+       ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
+       urcu_posix_assert(!ret);
+
        return workqueue;
 }
 
@@ -455,13 +475,23 @@ void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue)
 void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue)
 {
        int ret;
+       sigset_t newmask, oldmask;
 
        /* Clear workqueue state from parent. */
        workqueue->flags &= ~URCU_WORKQUEUE_PAUSED;
        workqueue->flags &= ~URCU_WORKQUEUE_PAUSE;
        workqueue->tid = 0;
+
+       ret = sigfillset(&newmask);
+       urcu_posix_assert(!ret);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
+       urcu_posix_assert(!ret);
+
        ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
        if (ret) {
                urcu_die(ret);
        }
+
+       ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
+       urcu_posix_assert(!ret);
 }