Fix: call_rcu: teardown default call_rcu worker on application exit

[urcu.git] / src / urcu.c

diff --git a/src/urcu.c b/src/urcu.c
index e64432f8bb7034cf3ef63cacc03aca7884133b74..d81e84fde88e27de5c6ac28145c03cc5c6cf989d 100644 (file)
--- a/src/urcu.c
+++ b/src/urcu.c
@@ -113,9 +113,11 @@ void alias_rcu_init(void);
 static int init_done;
 
 void __attribute__((constructor)) rcu_init(void);
-void __attribute__((destructor)) rcu_exit(void);
 #endif
 
+void __attribute__((destructor)) rcu_exit(void);
+static void urcu_call_rcu_exit(void);
+
 /*
  * rcu_gp_lock ensures mutual exclusion between threads calling
  * synchronize_rcu().
@@ -266,17 +268,25 @@ static void wait_gp(void)
        smp_mb_master();
        /* Temporarily unlock the registry lock. */
        mutex_unlock(&rcu_registry_lock);
-       if (uatomic_read(&rcu_gp.futex) != -1)
-               goto end;
-       while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1,
-                       NULL, NULL, 0)) {
+       while (uatomic_read(&rcu_gp.futex) == -1) {
+               if (!futex_async(&rcu_gp.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. */
                        goto end;
                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);
@@ -663,22 +673,24 @@ void rcu_init(void)
 URCU_ATTR_ALIAS(urcu_stringify(rcu_init))
 void alias_rcu_init(void);
 
+/*
+ * Don't unregister the SIGRCU signal handler anymore, because
+ * call_rcu threads could still be using it shortly before the
+ * application exits.
+ * Assertion disabled because call_rcu threads are now rcu
+ * readers, and left running at exit.
+ * assert(cds_list_empty(&registry));
+ */
+
+#endif /* #ifdef RCU_SIGNAL */
+
 void rcu_exit(void)
 {
-       /*
-        * Don't unregister the SIGRCU signal handler anymore, because
-        * call_rcu threads could still be using it shortly before the
-        * application exits.
-        * Assertion disabled because call_rcu threads are now rcu
-        * readers, and left running at exit.
-        * assert(cds_list_empty(&registry));
-        */
+       urcu_call_rcu_exit();
 }
 URCU_ATTR_ALIAS(urcu_stringify(rcu_exit))
 void alias_rcu_exit(void);
 
-#endif /* #ifdef RCU_SIGNAL */
-
 DEFINE_RCU_FLAVOR(rcu_flavor);
 DEFINE_RCU_FLAVOR_ALIAS(rcu_flavor, alias_rcu_flavor);