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 f96553365ba4f51035f427798edd2ac4eb981f13..603cc85fc368561efc38eb9cf1ed705fa5c97378 100644 (file)
--- 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)