wfcqueue: return whether dequeue is dequeuing last element
authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Mon, 6 May 2013 13:33:36 +0000 (09:33 -0400)
committerMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Mon, 6 May 2013 13:33:36 +0000 (09:33 -0400)
Newly introduced "with_state" dequeue API members return queue state
atomically sampled with the dequeue operation.

Allow testing behavior of dequeue with respect to number of
enqueue-to-empty and splice-from-non-empty.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
urcu/static/wfcqueue.h
urcu/wfcqueue.h
wfcqueue.c

index af7a8c6..62e003f 100644 (file)
@@ -350,18 +350,24 @@ ___cds_wfcq_next_nonblocking(struct cds_wfcq_head *head,
 }
 
 static inline struct cds_wfcq_node *
-___cds_wfcq_dequeue(struct cds_wfcq_head *head,
+___cds_wfcq_dequeue_with_state(struct cds_wfcq_head *head,
                struct cds_wfcq_tail *tail,
+               int *state,
                int blocking)
 {
        struct cds_wfcq_node *node, *next;
 
-       if (_cds_wfcq_empty(head, tail))
+       if (state)
+               *state = 0;
+
+       if (_cds_wfcq_empty(head, tail)) {
                return NULL;
+       }
 
        node = ___cds_wfcq_node_sync_next(&head->node, blocking);
-       if (!blocking && node == CDS_WFCQ_WOULDBLOCK)
+       if (!blocking && node == CDS_WFCQ_WOULDBLOCK) {
                return CDS_WFCQ_WOULDBLOCK;
+       }
 
        if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
                /*
@@ -379,8 +385,11 @@ ___cds_wfcq_dequeue(struct cds_wfcq_head *head,
                 * content.
                 */
                _cds_wfcq_node_init(&head->node);
-               if (uatomic_cmpxchg(&tail->p, node, &head->node) == node)
+               if (uatomic_cmpxchg(&tail->p, node, &head->node) == node) {
+                       if (state)
+                               *state |= CDS_WFCQ_STATE_LAST;
                        return node;
+               }
                next = ___cds_wfcq_node_sync_next(node, blocking);
                /*
                 * In nonblocking mode, if we would need to block to
@@ -404,7 +413,7 @@ ___cds_wfcq_dequeue(struct cds_wfcq_head *head,
 }
 
 /*
- * __cds_wfcq_dequeue_blocking: dequeue a node from the queue.
+ * __cds_wfcq_dequeue_with_state_blocking: dequeue node from queue, with state.
  *
  * Content written into the node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
@@ -413,23 +422,49 @@ ___cds_wfcq_dequeue(struct cds_wfcq_head *head,
  * caller.
  */
 static inline struct cds_wfcq_node *
+___cds_wfcq_dequeue_with_state_blocking(struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail, int *state)
+{
+       return ___cds_wfcq_dequeue_with_state(head, tail, state, 1);
+}
+
+/*
+ * ___cds_wfcq_dequeue_blocking: dequeue node from queue.
+ *
+ * Same as __cds_wfcq_dequeue_with_state_blocking, but without saving
+ * state.
+ */
+static inline struct cds_wfcq_node *
 ___cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head,
                struct cds_wfcq_tail *tail)
 {
-       return ___cds_wfcq_dequeue(head, tail, 1);
+       return ___cds_wfcq_dequeue_with_state_blocking(head, tail, NULL);
 }
 
 /*
- * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
+ * __cds_wfcq_dequeue_with_state_nonblocking: dequeue node, with state.
  *
  * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK
  * if it needs to block.
  */
 static inline struct cds_wfcq_node *
+___cds_wfcq_dequeue_with_state_nonblocking(struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail, int *state)
+{
+       return ___cds_wfcq_dequeue_with_state(head, tail, state, 0);
+}
+
+/*
+ * ___cds_wfcq_dequeue_nonblocking: dequeue node from queue.
+ *
+ * Same as __cds_wfcq_dequeue_with_state_nonblocking, but without saving
+ * state.
+ */
+static inline struct cds_wfcq_node *
 ___cds_wfcq_dequeue_nonblocking(struct cds_wfcq_head *head,
                struct cds_wfcq_tail *tail)
 {
-       return ___cds_wfcq_dequeue(head, tail, 0);
+       return ___cds_wfcq_dequeue_with_state_nonblocking(head, tail, NULL);
 }
 
 /*
@@ -532,7 +567,7 @@ ___cds_wfcq_splice_nonblocking(
 }
 
 /*
- * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
+ * cds_wfcq_dequeue_with_state_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.
@@ -541,17 +576,29 @@ ___cds_wfcq_splice_nonblocking(
  * It is valid to reuse and free a dequeued node immediately.
  */
 static inline struct cds_wfcq_node *
-_cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head,
-               struct cds_wfcq_tail *tail)
+_cds_wfcq_dequeue_with_state_blocking(struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail, int *state)
 {
        struct cds_wfcq_node *retval;
 
        _cds_wfcq_dequeue_lock(head, tail);
-       retval = ___cds_wfcq_dequeue_blocking(head, tail);
+       retval = ___cds_wfcq_dequeue_with_state_blocking(head, tail, state);
        _cds_wfcq_dequeue_unlock(head, tail);
        return retval;
 }
 
+/*
+ * cds_wfcq_dequeue_blocking: dequeue node from queue.
+ *
+ * Same as cds_wfcq_dequeue_blocking, but without saving state.
+ */
+static inline struct cds_wfcq_node *
+_cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail)
+{
+       return _cds_wfcq_dequeue_with_state_blocking(head, tail, NULL);
+}
+
 /*
  * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
  *
index 4ce8fe9..652b42d 100644 (file)
@@ -52,6 +52,10 @@ enum cds_wfcq_ret {
        CDS_WFCQ_RET_SRC_EMPTY =        2,
 };
 
+enum cds_wfcq_state {
+       CDS_WFCQ_STATE_LAST =           (1U << 0),
+};
+
 struct cds_wfcq_node {
        struct cds_wfcq_node *next;
 };
@@ -85,12 +89,16 @@ struct cds_wfcq_tail {
 
 /* Locking performed within cds_wfcq calls. */
 #define cds_wfcq_dequeue_blocking      _cds_wfcq_dequeue_blocking
+#define cds_wfcq_dequeue_with_state_blocking   \
+                                       _cds_wfcq_dequeue_with_state_blocking
 #define cds_wfcq_splice_blocking       _cds_wfcq_splice_blocking
 #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() */
 #define __cds_wfcq_dequeue_blocking    ___cds_wfcq_dequeue_blocking
+#define __cds_wfcq_dequeue_with_state_blocking \
+                                       ___cds_wfcq_dequeue_with_state_blocking
 #define __cds_wfcq_splice_blocking     ___cds_wfcq_splice_blocking
 #define __cds_wfcq_first_blocking      ___cds_wfcq_first_blocking
 #define __cds_wfcq_next_blocking       ___cds_wfcq_next_blocking
@@ -101,6 +109,8 @@ struct cds_wfcq_tail {
  * need to block. splice returns nonzero if it needs to block.
  */
 #define __cds_wfcq_dequeue_nonblocking ___cds_wfcq_dequeue_nonblocking
+#define __cds_wfcq_dequeue_with_state_nonblocking      \
+                               ___cds_wfcq_dequeue_with_state_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
@@ -199,6 +209,17 @@ extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
                struct cds_wfcq_head *head,
                struct cds_wfcq_tail *tail);
 
+/*
+ * cds_wfcq_dequeue_with_state_blocking: dequeue with state.
+ *
+ * Same as cds_wfcq_dequeue_blocking, but saves whether dequeueing the
+ * last node of the queue into state (CDS_WFCQ_STATE_LAST).
+ */
+extern struct cds_wfcq_node *cds_wfcq_dequeue_with_state_blocking(
+               struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail,
+               int *state);
+
 /*
  * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
  *
@@ -231,6 +252,17 @@ extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
                struct cds_wfcq_head *head,
                struct cds_wfcq_tail *tail);
 
+/*
+ * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
+ *
+ * Same as __cds_wfcq_dequeue_blocking, but saves whether dequeueing the
+ * last node of the queue into state (CDS_WFCQ_STATE_LAST).
+ */
+extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_blocking(
+               struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail,
+               int *state);
+
 /*
  * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
  *
@@ -241,6 +273,17 @@ extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
                struct cds_wfcq_head *head,
                struct cds_wfcq_tail *tail);
 
+/*
+ * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
+ *
+ * Same as __cds_wfcq_dequeue_nonblocking, but saves whether dequeueing
+ * the last node of the queue into state (CDS_WFCQ_STATE_LAST).
+ */
+extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_nonblocking(
+               struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail,
+               int *state);
+
 /*
  * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
  *
index ab0eb93..4950c10 100644 (file)
@@ -73,6 +73,14 @@ struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
        return _cds_wfcq_dequeue_blocking(head, tail);
 }
 
+struct cds_wfcq_node *cds_wfcq_dequeue_with_state_blocking(
+               struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail,
+               int *state)
+{
+       return _cds_wfcq_dequeue_with_state_blocking(head, tail, state);
+}
+
 enum cds_wfcq_ret cds_wfcq_splice_blocking(
                struct cds_wfcq_head *dest_q_head,
                struct cds_wfcq_tail *dest_q_tail,
@@ -90,6 +98,14 @@ struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
        return ___cds_wfcq_dequeue_blocking(head, tail);
 }
 
+struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_blocking(
+               struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail,
+               int *state)
+{
+       return ___cds_wfcq_dequeue_with_state_blocking(head, tail, state);
+}
+
 struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
                struct cds_wfcq_head *head,
                struct cds_wfcq_tail *tail)
@@ -97,6 +113,14 @@ struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
        return ___cds_wfcq_dequeue_nonblocking(head, tail);
 }
 
+struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_nonblocking(
+               struct cds_wfcq_head *head,
+               struct cds_wfcq_tail *tail,
+               int *state)
+{
+       return ___cds_wfcq_dequeue_with_state_nonblocking(head, tail, state);
+}
+
 enum cds_wfcq_ret __cds_wfcq_splice_blocking(
                struct cds_wfcq_head *dest_q_head,
                struct cds_wfcq_tail *dest_q_tail,
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