Fix: Always check pthread_create for failures

[urcu.git] / src / urcu-defer-impl.h

diff --git a/src/urcu-defer-impl.h b/src/urcu-defer-impl.h
index d25e9b93f4dc17e8f1e6ee986ad04cdca366527f..cbb0ca8565bfe2b52806e343f7f61d09117d6f8c 100644 (file)
--- 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);
@@ -401,8 +409,18 @@ void defer_rcu(void (*fct)(void *p), void *p)
 static void start_defer_thread(void)
 {
        int ret;
+       sigset_t newmask, oldmask;
+
+       ret = sigfillset(&newmask);
+       urcu_posix_assert(!ret);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
+       urcu_posix_assert(!ret);
 
        ret = pthread_create(&tid_defer, NULL, thr_defer, NULL);
+       if (ret)
+               urcu_die(ret);
+
+       ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
        urcu_posix_assert(!ret);
 }