wfcqueue tests: use dequeue empty state

[urcu.git] / urcu / static / wfstack.h

diff --git a/urcu/static/wfstack.h b/urcu/static/wfstack.h
index 24f6cb478447e76ec0be88b6a86beb28b129e83c..9bc9519f16f43c87a65974ad1697fecfb242d94e 100644 (file)
--- a/urcu/static/wfstack.h
+++ b/urcu/static/wfstack.h
@@ -47,9 +47,10 @@ extern "C" {
  * Stack implementing push, pop, pop_all operations, as well as iterator
  * on the stack head returned by pop_all.
  *
- * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all.
- * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, iteration on stack
- *                      head returned by pop_all.
+ * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
+ *                       cds_wfs_first.
+ * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
+ *                      iteration on stack head returned by pop_all.
  *
  * Synchronization table:
  *
@@ -136,7 +137,7 @@ int _cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node)
  * Waiting for push to complete enqueue and return the next node.
  */
 static inline struct cds_wfs_node *
-___cds_wfs_node_sync_next(struct cds_wfs_node *node)
+___cds_wfs_node_sync_next(struct cds_wfs_node *node, int blocking)
 {
        struct cds_wfs_node *next;
        int attempt = 0;
@@ -145,6 +146,8 @@ ___cds_wfs_node_sync_next(struct cds_wfs_node *node)
         * Adaptative busy-looping waiting for push to complete.
         */
        while ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
+               if (!blocking)
+                       return CDS_WFS_WOULDBLOCK;
                if (++attempt >= CDS_WFS_ADAPT_ATTEMPTS) {
                        poll(NULL, 0, CDS_WFS_WAIT);    /* Wait for 10ms */
                        attempt = 0;
@@ -156,6 +159,29 @@ ___cds_wfs_node_sync_next(struct cds_wfs_node *node)
        return next;
 }
 
+static inline
+struct cds_wfs_node *
+___cds_wfs_pop(struct cds_wfs_stack *s, int blocking)
+{
+       struct cds_wfs_head *head, *new_head;
+       struct cds_wfs_node *next;
+
+       for (;;) {
+               head = CMM_LOAD_SHARED(s->head);
+               if (___cds_wfs_end(head))
+                       return NULL;
+               next = ___cds_wfs_node_sync_next(&head->node, blocking);
+               if (!blocking && next == CDS_WFS_WOULDBLOCK)
+                       return CDS_WFS_WOULDBLOCK;
+               new_head = caa_container_of(next, struct cds_wfs_head, node);
+               if (uatomic_cmpxchg(&s->head, head, new_head) == head)
+                       return &head->node;
+               if (!blocking)
+                       return CDS_WFS_WOULDBLOCK;
+               /* busy-loop if head changed under us */
+       }
+}
+
 /*
  * __cds_wfs_pop_blocking: pop a node from the stack.
  *
@@ -176,19 +202,20 @@ static inline
 struct cds_wfs_node *
 ___cds_wfs_pop_blocking(struct cds_wfs_stack *s)
 {
-       struct cds_wfs_head *head, *new_head;
-       struct cds_wfs_node *next;
+       return ___cds_wfs_pop(s, 1);
+}
 
-       for (;;) {
-               head = CMM_LOAD_SHARED(s->head);
-               if (___cds_wfs_end(head))
-                       return NULL;
-               next = ___cds_wfs_node_sync_next(&head->node);
-               new_head = caa_container_of(next, struct cds_wfs_head, node);
-               if (uatomic_cmpxchg(&s->head, head, new_head) == head)
-                       return &head->node;
-               /* busy-loop if head changed under us */
-       }
+/*
+ * __cds_wfs_pop_nonblocking: pop a node from the stack.
+ *
+ * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
+ * it needs to block.
+ */
+static inline
+struct cds_wfs_node *
+___cds_wfs_pop_nonblocking(struct cds_wfs_stack *s)
+{
+       return ___cds_wfs_pop(s, 0);
 }
 
 /*
@@ -283,7 +310,7 @@ _cds_wfs_pop_all_blocking(struct cds_wfs_stack *s)
 }
 
 /*
- * cds_wfs_first_blocking: get first node of a popped stack.
+ * cds_wfs_first: get first node of a popped stack.
  *
  * Content written into the node before enqueue is guaranteed to be
  * consistent, but no other memory ordering is ensured.
@@ -291,15 +318,33 @@ _cds_wfs_pop_all_blocking(struct cds_wfs_stack *s)
  * Used by for-like iteration macros in urcu/wfstack.h:
  * cds_wfs_for_each_blocking()
  * cds_wfs_for_each_blocking_safe()
+ *
+ * Returns NULL if popped stack is empty, top stack node otherwise.
  */
 static inline struct cds_wfs_node *
-_cds_wfs_first_blocking(struct cds_wfs_head *head)
+_cds_wfs_first(struct cds_wfs_head *head)
 {
        if (___cds_wfs_end(head))
                return NULL;
        return &head->node;
 }
 
+static inline struct cds_wfs_node *
+___cds_wfs_next(struct cds_wfs_node *node, int blocking)
+{
+       struct cds_wfs_node *next;
+
+       next = ___cds_wfs_node_sync_next(node, blocking);
+       /*
+        * CDS_WFS_WOULDBLOCK != CSD_WFS_END, so we can check for end
+        * even if ___cds_wfs_node_sync_next returns CDS_WFS_WOULDBLOCK,
+        * and still return CDS_WFS_WOULDBLOCK.
+        */
+       if (___cds_wfs_end(next))
+               return NULL;
+       return next;
+}
+
 /*
  * cds_wfs_next_blocking: get next node of a popped stack.
  *
@@ -309,16 +354,27 @@ _cds_wfs_first_blocking(struct cds_wfs_head *head)
  * Used by for-like iteration macros in urcu/wfstack.h:
  * cds_wfs_for_each_blocking()
  * cds_wfs_for_each_blocking_safe()
+ *
+ * Returns NULL if reached end of popped stack, non-NULL next stack
+ * node otherwise.
  */
 static inline struct cds_wfs_node *
 _cds_wfs_next_blocking(struct cds_wfs_node *node)
 {
-       struct cds_wfs_node *next;
+       return ___cds_wfs_next(node, 1);
+}
 
-       next = ___cds_wfs_node_sync_next(node);
-       if (___cds_wfs_end(next))
-               return NULL;
-       return next;
+
+/*
+ * cds_wfs_next_nonblocking: get next node of a popped stack.
+ *
+ * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
+ * needs to block.
+ */
+static inline struct cds_wfs_node *
+_cds_wfs_next_nonblocking(struct cds_wfs_node *node)
+{
+       return ___cds_wfs_next(node, 0);
 }
 
 #ifdef __cplusplus