lfqueue: update comments, cleanup

[urcu.git] / urcu / rculfqueue.h

diff --git a/urcu/rculfqueue.h b/urcu/rculfqueue.h
index d5c74288831d32e810a045fc068c668e7d60347f..fa54ca55a47d4a6b5e5368851abf53fde2b3fb8f 100644 (file)
--- a/urcu/rculfqueue.h
+++ b/urcu/rculfqueue.h
@@ -30,10 +30,6 @@
 extern "C" {
 #endif
 
-#if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
-#error "Dynamic loader LGPL wrappers not implemented yet"
-#endif
-
 /*
  * Lock-free RCU queue using reference counting. Enqueue and dequeue operations
  * hold a RCU read lock to deal with cmpxchg ABA problem. This implementation
@@ -44,108 +40,56 @@ extern "C" {
  * which point their reference count will be decremented.
  */
 
-#define URCU_LFQ_PERMANENT_REF         128
+struct cds_lfq_queue_rcu;
 
-struct rcu_lfq_node {
-       struct rcu_lfq_node *next;
+struct cds_lfq_node_rcu {
+       struct cds_lfq_node_rcu *next;
        struct urcu_ref ref;
+       struct cds_lfq_queue_rcu *queue;
+       struct rcu_head rcu_head;
 };
 
-struct rcu_lfq_queue {
-       struct rcu_lfq_node *head, *tail;
-       struct rcu_lfq_node init;       /* Dummy initialization node */
+struct cds_lfq_queue_rcu {
+       struct cds_lfq_node_rcu *head, *tail;
+       struct cds_lfq_node_rcu init;   /* Dummy initialization node */
+       void (*release)(struct urcu_ref *ref);
 };
 
-void rcu_lfq_node_init(struct rcu_lfq_node *node)
-{
-       node->next = NULL;
-       urcu_ref_init(&node->ref);
-}
+#ifdef _LGPL_SOURCE
 
-void rcu_lfq_init(struct rcu_lfq_queue *q)
-{
-       rcu_lfq_node_init(&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;
-}
+#include <urcu/rculfqueue-static.h>
 
-void rcu_lfq_enqueue(struct rcu_lfq_queue *q, struct rcu_lfq_node *node)
-{
-       urcu_ref_get(&node->ref);
-
-       /*
-        * uatomic_cmpxchg() implicit memory barrier orders earlier stores to
-        * node before publication.
-        */
-
-       for (;;) {
-               struct rcu_lfq_node *tail, *next;
-
-               rcu_read_lock();
-               tail = rcu_dereference(q->tail);
-               /*
-                * Typically expect tail->next to be NULL.
-                */
-               next = uatomic_cmpxchg(&tail->next, NULL, node);
-               if (next == NULL) {
-                       /*
-                        * Tail was at the end of queue, we successfully
-                        * appended to it.
-                        * Now move tail (another enqueue might beat
-                        * us to it, that's fine).
-                        */
-                       uatomic_cmpxchg(&q->tail, tail, node);
-                       rcu_read_unlock();
-                       return;
-               } else {
-                       /*
-                        * Failure to append to current tail. Help moving tail
-                        * further and retry.
-                        */
-                       uatomic_cmpxchg(&q->tail, tail, next);
-                       rcu_read_unlock();
-                       continue;
-               }
-       }
-}
+#define cds_lfq_node_init_rcu          _cds_lfq_node_init_rcu
+#define cds_lfq_init_rcu               _cds_lfq_init_rcu
+#define cds_lfq_enqueue_rcu            _cds_lfq_enqueue_rcu
+#define cds_lfq_dequeue_rcu            _cds_lfq_dequeue_rcu
+
+#else /* !_LGPL_SOURCE */
+
+extern void cds_lfq_node_init_rcu(struct cds_lfq_node_rcu *node);
+extern void cds_lfq_init_rcu(struct cds_lfq_queue_rcu *q,
+                            void (*release)(struct urcu_ref *ref));
 
 /*
- * 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 rcu_lfq_node
- * structure.
+ * Should be called under rcu read lock critical section.
+ */
+extern 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.
+ *
+ * The entry returned by dequeue must be taken care of by doing a
+ * sequence of urcu_ref_put which release handler should do a call_rcu.
+ *
  * 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).
  */
-struct rcu_lfq_node *
-rcu_lfq_dequeue(struct rcu_lfq_queue *q, void (*release)(struct urcu_ref *))
-{
-       for (;;) {
-               struct rcu_lfq_node *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);
-                               return next;
-                       } else {
-                               /* Concurrently pushed, retry */
-                               rcu_read_unlock();
-                               continue;
-                       }
-               } else {
-                       /* Empty */
-                       rcu_read_unlock();
-                       return NULL;
-               }
-       }
-}
+extern
+struct cds_lfq_node_rcu *cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu *q);
+
+#endif /* !_LGPL_SOURCE */
 
 #ifdef __cplusplus
 }