X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=urcu%2Fstatic%2Fwfcqueue.h;h=a284b580af7d8777087ba17e6094c40e03abecc9;hb=dfb65fd3cc75f660f35feedd2e14b000dbe39a4b;hp=120a5989e6a4341c7d2ec8a4fc719812235542ae;hpb=47215721095cf47e110f113d26f9e61514405a4c;p=urcu.git

diff --git a/urcu/static/wfcqueue.h b/urcu/static/wfcqueue.h
index 120a598..a284b58 100644
--- a/urcu/static/wfcqueue.h
+++ b/urcu/static/wfcqueue.h
@@ -6,8 +6,8 @@
  *
  * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
  *
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See wfcqueue.h for linking
- * dynamically with the userspace rcu library.
+ * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/wfcqueue.h for
+ * linking dynamically with the userspace rcu library.
  *
  * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  * Copyright 2011-2012 - Lai Jiangshan <laijs@cn.fujitsu.com>
@@ -312,6 +312,8 @@ ___cds_wfcq_dequeue(struct cds_wfcq_head *head,
 		return NULL;
 
 	node = ___cds_wfcq_node_sync_next(&head->node, blocking);
+	if (!blocking && node == CDS_WFCQ_WOULDBLOCK)
+		return CDS_WFCQ_WOULDBLOCK;
 
 	if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
 		/*
@@ -332,6 +334,15 @@ ___cds_wfcq_dequeue(struct cds_wfcq_head *head,
 		if (uatomic_cmpxchg(&tail->p, node, &head->node) == node)
 			return node;
 		next = ___cds_wfcq_node_sync_next(node, blocking);
+		/*
+		 * In nonblocking mode, if we would need to block to
+		 * get node's next, set the head next node pointer
+		 * (currently NULL) back to its original value.
+		 */
+		if (!blocking && next == CDS_WFCQ_WOULDBLOCK) {
+			head->node.next = node;
+			return CDS_WFCQ_WOULDBLOCK;
+		}
 	}
 
 	/*