wfcqueue: return whether dequeue is dequeuing last element

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>

diff --git a/urcu/static/wfcqueue.h b/urcu/static/wfcqueue.h
index af7a8c6e7d4e3b1a7876347eb5cfb52db8e88046..62e003f98a4029a08f20e85b3a2c67f1b593ac03 100644 (file)
--- a/urcu/static/wfcqueue.h
+++ b/urcu/static/wfcqueue.h
@@ -350,18 +350,24 @@ ___cds_wfcq_next_nonblocking(struct cds_wfcq_head *head,
 }
 
 static inline struct cds_wfcq_node *
 }
 
 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,
                struct cds_wfcq_tail *tail,

+               int *state,

                int blocking)
 {
        struct cds_wfcq_node *node, *next;
 
                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;
                return NULL;

+       }

 
        node = ___cds_wfcq_node_sync_next(&head->node, blocking);
 
        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;
                return CDS_WFCQ_WOULDBLOCK;

+       }

 
        if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
                /*
 
        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);
                 * 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;
                        return node;

+               }

                next = ___cds_wfcq_node_sync_next(node, blocking);
                /*
                 * In nonblocking mode, if we would need to block to
                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.
  *
  * 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 *
  * 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)
 {
 ___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 *
  *
  * 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)
 {
 ___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.
  *
  * 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 *
  * 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);
 {
        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_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.
  *
 /*
  * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
  *

diff --git a/urcu/wfcqueue.h b/urcu/wfcqueue.h
index 4ce8fe962296406b7b69eb75992ea9d910ef6f08..652b42d3ab5da2adda7027f490af4230460a2448 100644 (file)
--- a/urcu/wfcqueue.h
+++ b/urcu/wfcqueue.h
@@ -52,6 +52,10 @@ enum cds_wfcq_ret {
        CDS_WFCQ_RET_SRC_EMPTY =        2,
 };
 
        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;
 };
 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
 
 /* 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_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
 #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
  * 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
 #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);
 
                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.
  *
 /*
  * 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);
 
                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.
  *
 /*
  * __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);
 
                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.
  *
 /*
  * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
  *

diff --git a/wfcqueue.c b/wfcqueue.c
index ab0eb939e912e15c4b8f44ca9d65d67df0a3b4cd..4950c1008ebbd69c51bff06ae6cf929ef4bc5b73 100644 (file)
--- a/wfcqueue.c
+++ b/wfcqueue.c
@@ -73,6 +73,14 @@ struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
        return _cds_wfcq_dequeue_blocking(head, tail);
 }
 
        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,
 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);
 }
 
        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)
 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);
 }
 
        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,
 enum cds_wfcq_ret __cds_wfcq_splice_blocking(
                struct cds_wfcq_head *dest_q_head,
                struct cds_wfcq_tail *dest_q_tail,