X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu%2Fwfcqueue.h;h=fe2862e28469051966c861c7cd3964772ef1db8a;hp=501120b2b36554ce95f43285be7c4843e97b36f7;hb=47215721095cf47e110f113d26f9e61514405a4c;hpb=f94061a3df4c9eab9ac869a19e4228de54771fcb

diff --git a/urcu/wfcqueue.h b/urcu/wfcqueue.h
index 501120b..fe2862e 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
  *
@@ -37,10 +37,14 @@ extern "C" {
 /*
  * Concurrent queue with wait-free enqueue/blocking dequeue.
  *
- * Inspired from half-wait-free/half-blocking queue implementation done by
- * Paul E. McKenney.
+ * This queue has been designed and implemented collaboratively by
+ * Mathieu Desnoyers and Lai Jiangshan. Inspired from
+ * half-wait-free/half-blocking queue implementation done by Paul E.
+ * McKenney.
  */
 
+#define CDS_WFCQ_WOULDBLOCK	((void *) -1UL)
+
 struct cds_wfcq_node {
 	struct cds_wfcq_node *next;
 };
@@ -84,6 +88,16 @@ 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 */
 
 /*
@@ -100,6 +114,10 @@ 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.
  */
 
 /*
@@ -149,7 +167,8 @@ 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,
@@ -162,7 +181,8 @@ 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.
  */
 extern void cds_wfcq_splice_blocking(
 		struct cds_wfcq_head *dest_q_head,
@@ -171,17 +191,28 @@ extern void cds_wfcq_splice_blocking(
 		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.
  *
@@ -189,7 +220,8 @@ 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.
  */
 extern void __cds_wfcq_splice_blocking(
 		struct cds_wfcq_head *dest_q_head,
@@ -197,12 +229,25 @@ extern void __cds_wfcq_splice_blocking(
 		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 nonzero if it needs to
+ * block.
+ */
+extern int __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,
+		struct cds_wfcq_tail *src_q_tail);
+
 /*
  * __cds_wfcq_first_blocking: get first 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()
@@ -212,12 +257,23 @@ 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()
@@ -228,6 +284,17 @@ 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 */
 
 /*
@@ -239,7 +306,8 @@ 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);	\
@@ -257,7 +325,8 @@ 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),		       \