CDS API: removal of rcu_read lock/unlock dep, removal of call_rcu argument from init

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

diff --git a/urcu/static/rculfqueue.h b/urcu/static/rculfqueue.h
index f3df7c01f2563bd3d5c7a29314d21ca1333d8a0a..99335c41ec41d33078279e2f843431111cf307e8 100644 (file)
--- a/urcu/static/rculfqueue.h
+++ b/urcu/static/rculfqueue.h
@@ -68,6 +68,7 @@ struct cds_lfq_node_rcu *make_dummy(struct cds_lfq_queue_rcu *q,
        dummy = malloc(sizeof(struct cds_lfq_node_rcu_dummy));
        assert(dummy);
        dummy->parent.next = next;
+       dummy->parent.dummy = 1;
        dummy->q = q;
        return &dummy->parent;
 }
@@ -85,8 +86,9 @@ void rcu_free_dummy(struct cds_lfq_node_rcu *node)
 {
        struct cds_lfq_node_rcu_dummy *dummy;
 
+       assert(node->dummy);
        dummy = caa_container_of(node, struct cds_lfq_node_rcu_dummy, parent);
-       dummy->q->queue_call_rcu(&dummy->head, free_dummy_cb);
+       call_rcu(&dummy->head, free_dummy_cb);
 }
 
 static inline
@@ -94,6 +96,7 @@ void free_dummy(struct cds_lfq_node_rcu *node)
 {
        struct cds_lfq_node_rcu_dummy *dummy;
 
+       assert(node->dummy);
        dummy = caa_container_of(node, struct cds_lfq_node_rcu_dummy, parent);
        free(dummy);
 }
@@ -102,17 +105,14 @@ static inline
 void _cds_lfq_node_init_rcu(struct cds_lfq_node_rcu *node)
 {
        node->next = NULL;
+       node->dummy = 0;
 }
 
 static inline
-void _cds_lfq_init_rcu(struct cds_lfq_queue_rcu *q,
-                      void queue_call_rcu(struct rcu_head *head,
-                               void (*func)(struct rcu_head *head)))
+void _cds_lfq_init_rcu(struct cds_lfq_queue_rcu *q)
 {
        q->tail = make_dummy(q, NULL);
-       q->dummy = q->tail;
        q->head = q->tail;
-       q->queue_call_rcu = queue_call_rcu;
 }
 
 /*
@@ -126,14 +126,14 @@ int _cds_lfq_destroy_rcu(struct cds_lfq_queue_rcu *q)
        struct cds_lfq_node_rcu *head;
 
        head = rcu_dereference(q->head);
-       if (!(head == q->dummy && head->next == NULL))
+       if (!(head->dummy && head->next == NULL))
                return -EPERM;  /* not empty */
        free_dummy(head);
        return 0;
 }
 
 /*
- * Should be called under rcu read lock critical section.
+ * Acts as a RCU reader.
  */
 static inline
 void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q,
@@ -147,6 +147,7 @@ void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q,
        for (;;) {
                struct cds_lfq_node_rcu *tail, *next;
 
+               rcu_read_lock();
                tail = rcu_dereference(q->tail);
                next = uatomic_cmpxchg(&tail->next, NULL, node);
                if (next == NULL) {
@@ -156,6 +157,7 @@ void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q,
                         * enqueue might beat us to it, that's fine).
                         */
                        (void) uatomic_cmpxchg(&q->tail, tail, node);
+                       rcu_read_unlock();
                        return;
                } else {
                        /*
@@ -163,28 +165,24 @@ void _cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q,
                         * Help moving tail further and retry.
                         */
                        (void) uatomic_cmpxchg(&q->tail, tail, next);
+                       rcu_read_unlock();
                        continue;
                }
        }
 }
 
 static inline
-void reenqueue_dummy(struct cds_lfq_queue_rcu *q)
+void enqueue_dummy(struct cds_lfq_queue_rcu *q)
 {
        struct cds_lfq_node_rcu *node;
 
        /* We need to reallocate to protect from ABA. */
        node = make_dummy(q, NULL);
-       if (uatomic_cmpxchg(&q->dummy, NULL, node) != NULL) {
-               /* other dequeue populated its new dummy */
-               free_dummy(node);
-               return;
-       }
        _cds_lfq_enqueue_rcu(q, node);
 }
 
 /*
- * Should be called under rcu read lock critical section.
+ * Acts as a RCU reader.
  *
  * The caller must wait for a grace period to pass before freeing the returned
  * node or modifying the cds_lfq_node_rcu structure.
@@ -194,38 +192,37 @@ static inline
 struct cds_lfq_node_rcu *_cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu *q)
 {
        for (;;) {
-               struct cds_lfq_node_rcu *head, *next, *dummy;
+               struct cds_lfq_node_rcu *head, *next;
 
+               rcu_read_lock();
                head = rcu_dereference(q->head);
                next = rcu_dereference(head->next);
-               dummy = rcu_dereference(q->dummy);
-               if (head == dummy && next == NULL)
+               if (head->dummy && next == NULL) {
+                       rcu_read_unlock();
                        return NULL;    /* empty */
+               }
                /*
                 * We never, ever allow dequeue to get to a state where
                 * the queue is empty (we need at least one node in the
                 * queue). This is ensured by checking if the head next
-                * is NULL. This means a concurrent dummy node
-                * re-enqueue is in progress. We help it reach
-                * completion, and retry.
+                * is NULL, which means we need to enqueue a dummy node
+                * before we can hope dequeuing anything.
                 */
                if (!next) {
-                       /*
-                        * Dummy node re-enqueue is in progress. Try to
-                        * help.
-                        */
-                       reenqueue_dummy(q);
-                       continue;       /* try again */
+                       enqueue_dummy(q);
+                       next = rcu_dereference(head->next);
                }
-               if (uatomic_cmpxchg(&q->head, head, next) != head)
+               if (uatomic_cmpxchg(&q->head, head, next) != head) {
+                       rcu_read_unlock();
                        continue;       /* Concurrently pushed. */
-               if (head == dummy) {
-                       /* Free old and requeue new dummy. */
-                       rcu_set_pointer(&q->dummy, NULL);
-                       rcu_free_dummy(dummy);
-                       reenqueue_dummy(q);
+               }
+               if (head->dummy) {
+                       /* Free dummy after grace period. */
+                       rcu_free_dummy(head);
+                       rcu_read_unlock();
                        continue;       /* try again */
                }
+               rcu_read_unlock();
                return head;
        }
 }