X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=urcu%2Fwfcqueue.h;h=ba2f2edd93276f4f257d4a9c8498f616f3940a03;hb=b9c2790452412b7dc3bc1eba2675afc6912f9a1e;hp=5576cbf4a5c0d928a068817019fea196b5f9174e;hpb=8ad4ce587f001ae026d5560ac509c2e48986130b;p=urcu.git

diff --git a/urcu/wfcqueue.h b/urcu/wfcqueue.h
index 5576cbf..ba2f2ed 100644
--- a/urcu/wfcqueue.h
+++ b/urcu/wfcqueue.h
@@ -37,8 +37,10 @@ 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.
  */
 
 struct cds_wfcq_node {
@@ -91,14 +93,19 @@ struct cds_wfcq_tail {
  *
  * Unless otherwise stated, the caller must ensure mutual exclusion of
  * queue update operations "dequeue" and "splice" (for source queue).
- * Queue read operations "first" and "next" need to be protected against
- * concurrent "dequeue" and "splice" (for source queue) by the caller.
+ * Queue read operations "first" and "next", which are used by
+ * "for_each" iterations, need to be protected against concurrent
+ * "dequeue" and "splice" (for source queue) by the caller.
  * "enqueue", "splice" (for destination queue), and "empty" are the only
  * operations that can be used without any mutual exclusion.
  * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
  *
  * 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.
  */
 
 /*
@@ -148,7 +155,8 @@ 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,
@@ -161,7 +169,8 @@ 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,
@@ -175,7 +184,8 @@ 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.
  * 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,
@@ -188,7 +198,8 @@ 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,
@@ -201,7 +212,12 @@ 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()
+ * __cds_wfcq_for_each_blocking_safe()
  */
 extern struct cds_wfcq_node *__cds_wfcq_first_blocking(
 		struct cds_wfcq_head *head,
@@ -212,7 +228,12 @@ extern struct cds_wfcq_node *__cds_wfcq_first_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()
+ * __cds_wfcq_for_each_blocking_safe()
  */
 extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
 		struct cds_wfcq_head *head,
@@ -230,7 +251,8 @@ 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);	\
@@ -248,7 +270,8 @@ 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),		       \