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 58ca1ab2627e91ac62f452fcee9ec03196659717..36b7659461bbb55d0da9e5c2e4269c0a362b09a8 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);
@@ -265,7 +273,7 @@ void rcu_defer_barrier_thread(void)
        _rcu_defer_barrier_thread();
        mutex_unlock(&rcu_defer_mutex);
 }
-__attribute__((alias(urcu_stringify(rcu_defer_barrier_thread))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_barrier_thread))
 void alias_rcu_defer_barrier_thread();
 
 /*
@@ -307,7 +315,7 @@ void rcu_defer_barrier(void)
 end:
        mutex_unlock(&rcu_defer_mutex);
 }
-__attribute__((alias(urcu_stringify(rcu_defer_barrier))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_barrier))
 void alias_rcu_defer_barrier();
 
 /*
@@ -376,7 +384,7 @@ 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 (;;) {
                /*
@@ -401,14 +409,15 @@ void defer_rcu(void (*fct)(void *p), void *p)
 {
        _defer_rcu(fct, p);
 }
-__attribute__((alias(urcu_stringify(defer_rcu)))) void alias_defer_rcu();
+URCU_ATTR_ALIAS(urcu_stringify(defer_rcu)) void alias_defer_rcu();
 
 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)
@@ -450,7 +459,7 @@ int rcu_defer_register_thread(void)
        mutex_unlock(&defer_thread_mutex);
        return 0;
 }
-__attribute__((alias(urcu_stringify(rcu_defer_register_thread))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_register_thread))
 int alias_rcu_defer_register_thread();
 
 void rcu_defer_unregister_thread(void)
@@ -470,14 +479,14 @@ void rcu_defer_unregister_thread(void)
                stop_defer_thread();
        mutex_unlock(&defer_thread_mutex);
 }
-__attribute__((alias(urcu_stringify(rcu_defer_unregister_thread))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_unregister_thread))
 void alias_rcu_defer_unregister_thread();
 
 void rcu_defer_exit(void)
 {
        assert(cds_list_empty(&registry_defer));
 }
-__attribute__((alias(urcu_stringify(rcu_defer_exit))))
+URCU_ATTR_ALIAS(urcu_stringify(rcu_defer_exit))
 void alias_rcu_defer_exit();
 
 #endif /* _URCU_DEFER_IMPL_H */