X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=urcu-qsbr.c;h=f5103eeea78351b64cb64a4cf99b2faca835d771;hb=63ff4873e046ba582d20e79ebff16ee7da2aa92f;hp=5c6eaa014721267da7de5f85fff22835d41a80b2;hpb=4d1ce26fea0296ff67791c881836393fdd020cf9;p=urcu.git

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 5c6eaa0..f5103ee 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -39,6 +39,8 @@
 
 static pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
 
+int gp_futex;
+
 /*
  * Global grace period counter.
  */
@@ -99,6 +101,27 @@ static void internal_urcu_unlock(void)
 	}
 }
 
+/*
+ * synchronize_rcu() waiting. Single thread.
+ */
+static void wait_gp(struct reader_registry *index)
+{
+	uatomic_dec(&gp_futex);
+	smp_mb(); /* Write futex before read reader_gp */
+	if (!rcu_gp_ongoing(index->rcu_reader_qs_gp)) {
+		/* Read reader_gp before write futex */
+		smp_mb();
+		/* Callbacks are queued, don't wait. */
+		uatomic_set(&gp_futex, 0);
+	} else {
+		/* Read reader_gp before read futex */
+		smp_rmb();
+		if (uatomic_read(&gp_futex) == -1)
+			futex(&gp_futex, FUTEX_WAIT, -1,
+			      NULL, NULL, 0);
+	}
+}
+
 static void wait_for_quiescent_state(void)
 {
 	struct reader_registry *index;
@@ -109,13 +132,19 @@ static void wait_for_quiescent_state(void)
 	 * Wait for each thread rcu_reader_qs_gp count to become 0.
 	 */
 	for (index = registry; index < registry + num_readers; index++) {
+		int wait_loops = 0;
+
+		while (rcu_gp_ongoing(index->rcu_reader_qs_gp)) {
+			if (wait_loops++ == RCU_QS_ACTIVE_ATTEMPTS) {
+				wait_gp(index);
+			} else {
 #ifndef HAS_INCOHERENT_CACHES
-		while (rcu_gp_ongoing(index->rcu_reader_qs_gp))
-			cpu_relax();
+				cpu_relax();
 #else /* #ifndef HAS_INCOHERENT_CACHES */
-		while (rcu_gp_ongoing(index->rcu_reader_qs_gp))
-			smp_mb();
+				smp_mb();
 #endif /* #else #ifndef HAS_INCOHERENT_CACHES */
+			}
+		}
 	}
 }
 
@@ -258,13 +287,13 @@ void *rcu_assign_pointer_sym(void **p, void *v)
 void *rcu_cmpxchg_pointer_sym(void **p, void *old, void *_new)
 {
 	wmb();
-	return cmpxchg(p, old, _new);
+	return uatomic_cmpxchg(p, old, _new);
 }
 
 void *rcu_xchg_pointer_sym(void **p, void *v)
 {
 	wmb();
-	return xchg(p, v);
+	return uatomic_xchg(p, v);
 }
 
 void *rcu_publish_content_sym(void **p, void *v)