X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu%2Fwfcqueue.h;h=ddf6b87c478eb808d72fbeb8242fb294726933c5;hp=b13aa7bd2076a5012df6594129ee5c11d5187494;hb=23773356a9fd12bf12627df437d0c7bd20e8ef01;hpb=ebfd2673f1ec2892bd3de86cd8bedc95ecf2a24e

diff --git a/urcu/wfcqueue.h b/urcu/wfcqueue.h
index b13aa7b..ddf6b87 100644
--- a/urcu/wfcqueue.h
+++ b/urcu/wfcqueue.h
@@ -2,7 +2,7 @@
 #define _URCU_WFCQUEUE_H
 
 /*
- * wfcqueue.h
+ * urcu/wfcqueue.h
  *
  * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
  *
@@ -43,6 +43,15 @@ extern "C" {
  * McKenney.
  */
 
+#define CDS_WFCQ_WOULDBLOCK	((void *) -1UL)
+
+enum cds_wfcq_ret {
+	CDS_WFCQ_RET_WOULDBLOCK = 	-1,
+	CDS_WFCQ_RET_DEST_EMPTY =	0,
+	CDS_WFCQ_RET_DEST_NON_EMPTY =	1,
+	CDS_WFCQ_RET_SRC_EMPTY = 	2,
+};
+
 struct cds_wfcq_node {
 	struct cds_wfcq_node *next;
 };
@@ -86,6 +95,16 @@ struct cds_wfcq_tail {
 #define __cds_wfcq_first_blocking	___cds_wfcq_first_blocking
 #define __cds_wfcq_next_blocking	___cds_wfcq_next_blocking
 
+/*
+ * Locking ensured by caller by holding cds_wfcq_dequeue_lock().
+ * Non-blocking: deque, first, next return CDS_WFCQ_WOULDBLOCK if they
+ * need to block. splice returns nonzero if it needs to block.
+ */
+#define __cds_wfcq_dequeue_nonblocking	___cds_wfcq_dequeue_nonblocking
+#define __cds_wfcq_splice_nonblocking	___cds_wfcq_splice_nonblocking
+#define __cds_wfcq_first_nonblocking	___cds_wfcq_first_nonblocking
+#define __cds_wfcq_next_nonblocking	___cds_wfcq_next_nonblocking
+
 #else /* !_LGPL_SOURCE */
 
 /*
@@ -102,6 +121,10 @@ struct cds_wfcq_tail {
  *
  * For convenience, cds_wfcq_dequeue_blocking() and
  * cds_wfcq_splice_blocking() hold the dequeue lock.
+ *
+ * Besides locking, mutual exclusion of dequeue, splice and iteration
+ * can be ensured by performing all of those operations from a single
+ * thread, without requiring any lock.
  */
 
 /*
@@ -140,8 +163,11 @@ extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
  *
  * Issues a full memory barrier before enqueue. No mutual exclusion is
  * required.
+ *
+ * Returns false if the queue was empty prior to adding the node.
+ * Returns true otherwise.
  */
-extern void cds_wfcq_enqueue(struct cds_wfcq_head *head,
+extern bool cds_wfcq_enqueue(struct cds_wfcq_head *head,
 		struct cds_wfcq_tail *tail,
 		struct cds_wfcq_node *node);
 
@@ -151,7 +177,8 @@ extern void cds_wfcq_enqueue(struct cds_wfcq_head *head,
  * Content written into the node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
  * It is valid to reuse and free a dequeued node immediately.
- * Mutual exlusion with dequeuers is ensured internally.
+ * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is
+ * ensured.
  */
 extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
 		struct cds_wfcq_head *head,
@@ -164,26 +191,41 @@ extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
  * dest_q must be already initialized.
  * Content written into the node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
- * Mutual exlusion with dequeuers is ensured internally.
+ * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is
+ * ensured.
+ *
+ * Returns enum cds_wfcq_ret which indicates the state of the src or
+ * dest queue. Cannot block.
  */
-extern void cds_wfcq_splice_blocking(
+extern enum cds_wfcq_ret cds_wfcq_splice_blocking(
 		struct cds_wfcq_head *dest_q_head,
 		struct cds_wfcq_tail *dest_q_tail,
 		struct cds_wfcq_head *src_q_head,
 		struct cds_wfcq_tail *src_q_tail);
 
 /*
- * __cds_wfcq_dequeue_blocking:
+ * __cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
  *
  * Content written into the node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
  * It is valid to reuse and free a dequeued node immediately.
- * Should be called with cds_wfcq_dequeue_lock() held.
+ * Dequeue/splice/iteration mutual exclusion should be ensured by the
+ * caller.
  */
 extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
 		struct cds_wfcq_head *head,
 		struct cds_wfcq_tail *tail);
 
+/*
+ * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
+ *
+ * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK
+ * if it needs to block.
+ */
+extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
+		struct cds_wfcq_head *head,
+		struct cds_wfcq_tail *tail);
+
 /*
  * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
  *
@@ -191,9 +233,25 @@ extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
  * dest_q must be already initialized.
  * Content written into the node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
- * Should be called with cds_wfcq_dequeue_lock() held.
+ * Dequeue/splice/iteration mutual exclusion for src_q should be ensured
+ * by the caller.
+ *
+ * Returns enum cds_wfcq_ret which indicates the state of the src or
+ * dest queue. Cannot block.
+ */
+extern enum cds_wfcq_ret __cds_wfcq_splice_blocking(
+		struct cds_wfcq_head *dest_q_head,
+		struct cds_wfcq_tail *dest_q_tail,
+		struct cds_wfcq_head *src_q_head,
+		struct cds_wfcq_tail *src_q_tail);
+
+/*
+ * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q.
+ *
+ * Same as __cds_wfcq_splice_blocking, but returns
+ * CDS_WFCQ_RET_WOULDBLOCK if it needs to block.
  */
-extern void __cds_wfcq_splice_blocking(
+extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking(
 		struct cds_wfcq_head *dest_q_head,
 		struct cds_wfcq_tail *dest_q_tail,
 		struct cds_wfcq_head *src_q_head,
@@ -204,7 +262,8 @@ extern void __cds_wfcq_splice_blocking(
  *
  * Content written into the node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
- * Should be called with cds_wfcq_dequeue_lock() held.
+ * Dequeue/splice/iteration mutual exclusion should be ensured by the
+ * caller.
  *
  * Used by for-like iteration macros:
  * __cds_wfcq_for_each_blocking()
@@ -214,12 +273,23 @@ extern struct cds_wfcq_node *__cds_wfcq_first_blocking(
 		struct cds_wfcq_head *head,
 		struct cds_wfcq_tail *tail);
 
+/*
+ * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing.
+ *
+ * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if
+ * it needs to block.
+ */
+extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking(
+		struct cds_wfcq_head *head,
+		struct cds_wfcq_tail *tail);
+
 /*
  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
  *
  * Content written into the node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
- * Should be called with cds_wfcq_dequeue_lock() held.
+ * Dequeue/splice/iteration mutual exclusion should be ensured by the
+ * caller.
  *
  * Used by for-like iteration macros:
  * __cds_wfcq_for_each_blocking()
@@ -230,6 +300,17 @@ extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
 		struct cds_wfcq_tail *tail,
 		struct cds_wfcq_node *node);
 
+/*
+ * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
+ *
+ * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if
+ * it needs to block.
+ */
+extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking(
+		struct cds_wfcq_head *head,
+		struct cds_wfcq_tail *tail,
+		struct cds_wfcq_node *node);
+
 #endif /* !_LGPL_SOURCE */
 
 /*
@@ -241,7 +322,8 @@ extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
  *
  * Content written into each node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
- * Should be called with cds_wfcq_dequeue_lock() held.
+ * Dequeue/splice/iteration mutual exclusion should be ensured by the
+ * caller.
  */
 #define __cds_wfcq_for_each_blocking(head, tail, node)		\
 	for (node = __cds_wfcq_first_blocking(head, tail);	\
@@ -259,7 +341,8 @@ extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
  *
  * Content written into each node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
- * Should be called with cds_wfcq_dequeue_lock() held.
+ * Dequeue/splice/iteration mutual exclusion should be ensured by the
+ * caller.
  */
 #define __cds_wfcq_for_each_blocking_safe(head, tail, node, n)		       \
 	for (node = __cds_wfcq_first_blocking(head, tail),		       \