X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-defer.c;h=412eb30477908b2a60acff9dde794d9ecfc793f8;hp=1e5d2b6d6dba842c3aaa13eae8aed8d92dd17ebc;hb=b55487c706982c8190e42545f7f74dfadad59548;hpb=786ee85b1676d2a1865b2db7120c45bafdf954d6

diff --git a/urcu-defer.c b/urcu-defer.c
index 1e5d2b6..412eb30 100644
--- a/urcu-defer.c
+++ b/urcu-defer.c
@@ -101,18 +101,31 @@ static void internal_urcu_unlock(pthread_mutex_t *mutex)
  * Must be called after Q.S. is reached.
  */
 static void rcu_defer_barrier_queue(struct defer_queue *queue,
-				      unsigned long head)
+				    unsigned long head)
 {
 	unsigned long i;
+	void (*fct)(void *p);
+	void *p;
 
 	/*
 	 * Tail is only modified when lock is held.
 	 * Head is only modified by owner thread.
 	 */
 
-	for (i = queue->tail; i != head; i++) {
+	for (i = queue->tail; i != head;) {
 		smp_rmb();       /* read head before q[]. */
-		free(LOAD_SHARED(queue->q[i & DEFER_QUEUE_MASK]));
+		p = LOAD_SHARED(queue->q[i++ & DEFER_QUEUE_MASK]);
+		if (unlikely(DQ_IS_FCT_BIT(p))) {
+			DQ_CLEAR_FCT_BIT(p);
+			queue->last_fct_out = p;
+			p = LOAD_SHARED(queue->q[i++ & DEFER_QUEUE_MASK]);
+		} else if (unlikely(p == DQ_FCT_MARK)) {
+			p = LOAD_SHARED(queue->q[i++ & DEFER_QUEUE_MASK]);
+			queue->last_fct_out = p;
+			p = LOAD_SHARED(queue->q[i++ & DEFER_QUEUE_MASK]);
+		}
+		fct = queue->last_fct_out;
+		fct(p);
 	}
 	smp_mb();	/* push tail after having used q[] */
 	STORE_SHARED(queue->tail, i);
@@ -120,9 +133,12 @@ static void rcu_defer_barrier_queue(struct defer_queue *queue,
 
 static void _rcu_defer_barrier_thread(void)
 {
-	unsigned long head;
+	unsigned long head, num_items;
 
 	head = defer_queue.head;
+	num_items = head - defer_queue.tail;
+	if (unlikely(!num_items))
+		return;
 	synchronize_rcu();
 	rcu_defer_barrier_queue(&defer_queue, head);
 }
@@ -135,20 +151,44 @@ void rcu_defer_barrier_thread(void)
 	internal_urcu_unlock(&urcu_defer_mutex);
 }
 
+/*
+ * rcu_defer_barrier - Execute all queued rcu callbacks.
+ *
+ * Execute all RCU callbacks queued before rcu_defer_barrier() execution.
+ * All callbacks queued on the local thread prior to a rcu_defer_barrier() call
+ * are guaranteed to be executed.
+ * Callbacks queued by other threads concurrently with rcu_defer_barrier()
+ * execution are not guaranteed to be executed in the current batch (could
+ * be left for the next batch). These callbacks queued by other threads are only
+ * guaranteed to be executed if there is explicit synchronization between
+ * the thread adding to the queue and the thread issuing the defer_barrier call.
+ */
+
 void rcu_defer_barrier(void)
 {
 	struct deferer_registry *index;
+	unsigned long num_items = 0;
 
 	if (!registry)
 		return;
 
 	internal_urcu_lock(&urcu_defer_mutex);
-	for (index = registry; index < registry + num_deferers; index++)
+	for (index = registry; index < registry + num_deferers; index++) {
 		index->last_head = LOAD_SHARED(index->defer_queue->head);
+		num_items += index->last_head - index->defer_queue->tail;
+	}
+	if (likely(!num_items)) {
+		/*
+		 * We skip the grace period because there are no queued
+		 * callbacks to execute.
+		 */
+		goto end;
+	}
 	synchronize_rcu();
 	for (index = registry; index < registry + num_deferers; index++)
 		rcu_defer_barrier_queue(index->defer_queue,
 					  index->last_head);
+end:
 	internal_urcu_unlock(&urcu_defer_mutex);
 }
 
@@ -168,9 +208,9 @@ void *thr_defer(void *args)
  * library wrappers to be used by non-LGPL compatible source code.
  */
 
-void rcu_defer_queue(void *p)
+void rcu_defer_queue(void (*fct)(void *p), void *p)
 {
-	_rcu_defer_queue(p);
+	_rcu_defer_queue(fct, p);
 }
 
 static void rcu_add_deferer(pthread_t id)
@@ -195,6 +235,7 @@ static void rcu_add_deferer(pthread_t id)
 	registry[num_deferers].tid = id;
 	/* reference to the TLS of _this_ deferer thread. */
 	registry[num_deferers].defer_queue = &defer_queue;
+	registry[num_deferers].last_head = 0;
 	num_deferers++;
 }
 
@@ -213,6 +254,7 @@ static void rcu_remove_deferer(pthread_t id)
 				sizeof(struct deferer_registry));
 			registry[num_deferers - 1].tid = 0;
 			registry[num_deferers - 1].defer_queue = NULL;
+			registry[num_deferers - 1].last_head = 0;
 			num_deferers--;
 			return;
 		}