cds containers: lfqueue and lfstack: don't depend on a particular rcu flavor

[urcu.git] / urcu / rculfqueue-static.h

diff --git a/urcu/rculfqueue-static.h b/urcu/rculfqueue-static.h
index d7c359f39e46906b910b544f5ebebb68cc2d242d..be6a4bc2b167958620afe336d56e73242405cf83 100644 (file)
--- a/urcu/rculfqueue-static.h
+++ b/urcu/rculfqueue-static.h
@@ -53,17 +53,24 @@ void _cds_lfq_node_init_rcu(struct cds_lfq_node_rcu *node)
        urcu_ref_init(&node->ref);
 }
 
-void _cds_lfq_init_rcu(struct cds_lfq_queue_rcu *q)
+void _cds_lfq_init_rcu(struct cds_lfq_queue_rcu *q,
+                      void (*release)(struct urcu_ref *ref))
 {
        _cds_lfq_node_init_rcu(&q->init);
        /* Make sure the initial node is never freed. */
        urcu_ref_set(&q->init.ref, URCU_LFQ_PERMANENT_REF);
        q->head = q->tail = &q->init;
+       q->release = release;
 }
 
-void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q, struct cds_lfq_node_rcu *node)
+/*
+ * Should be called under rcu read lock critical section.
+ */
+void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q,
+                         struct cds_lfq_node_rcu *node)
 {
        urcu_ref_get(&node->ref);
+       node->queue = q;
 
        /*
         * uatomic_cmpxchg() implicit memory barrier orders earlier stores to
@@ -73,7 +80,6 @@ void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q, struct cds_lfq_node_rcu *
        for (;;) {
                struct cds_lfq_node_rcu *tail, *next;
 
-               rcu_read_lock();
                tail = rcu_dereference(q->tail);
                /*
                 * Typically expect tail->next to be NULL.
@@ -87,7 +93,6 @@ void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q, struct cds_lfq_node_rcu *
                         * us to it, that's fine).
                         */
                        (void) uatomic_cmpxchg(&q->tail, tail, node);
-                       rcu_read_unlock();
                        return;
                } else {
                        /*
@@ -95,44 +100,39 @@ void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q, struct cds_lfq_node_rcu *
                         * further and retry.
                         */
                        (void) uatomic_cmpxchg(&q->tail, tail, next);
-                       rcu_read_unlock();
                        continue;
                }
        }
 }
 
 /*
- * The entry returned by dequeue must be taken care of by doing a urcu_ref_put,
- * which calls the release primitive when the reference count drops to zero. A
- * grace period must be waited after execution of the release callback before
- * performing the actual memory reclamation or modifying the cds_lfq_node_rcu
- * structure.
+ * Should be called under rcu read lock critical section.
+ *
+ * The entry returned by dequeue must be taken care of by doing a
+ * urcu_ref_put after a grace period passes.
+ *
  * In other words, the entry lfq node returned by dequeue must not be
  * modified/re-used/freed until the reference count reaches zero and a grace
- * period has elapsed (after the refcount reached 0).
+ * period has elapsed.
  */
 struct cds_lfq_node_rcu *
-_cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu *q, void (*release)(struct urcu_ref *))
+_cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu *q)
 {
        for (;;) {
                struct cds_lfq_node_rcu *head, *next;
 
-               rcu_read_lock();
                head = rcu_dereference(q->head);
                next = rcu_dereference(head->next);
                if (next) {
                        if (uatomic_cmpxchg(&q->head, head, next) == head) {
-                               rcu_read_unlock();
-                               urcu_ref_put(&head->ref, release);
+                               urcu_ref_put(&head->ref, q->release);
                                return next;
                        } else {
                                /* Concurrently pushed, retry */
-                               rcu_read_unlock();
                                continue;
                        }
                } else {
                        /* Empty */
-                       rcu_read_unlock();
                        return NULL;
                }
        }