* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
-#include <urcu/urcu_ref.h>
#include <assert.h>
+#include <urcu-call-rcu.h>
-#if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
-#error "Dynamic loader LGPL wrappers not implemented yet"
+#ifdef __cplusplus
+extern "C" {
#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
- * keeps a dummy head node to ensure we can always update the queue locklessly.
- * Given that this is a queue, the dummy head node must always advance as we
- * dequeue entries. Therefore, we keep a reference count on each entry we are
- * dequeueing, so they can be kept as dummy head node until the next dequeue, at
- * 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 urcu_ref ref;
+struct cds_lfq_node_rcu {
+ struct cds_lfq_node_rcu *next;
};
-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;
+ struct cds_lfq_node_rcu *tail;
+ void (*queue_call_rcu)(struct rcu_head *head,
+ void (*func)(struct rcu_head *head));
};
-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/static/rculfqueue.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_destroy_rcu _cds_lfq_destroy_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 queue_call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *head)));
+/*
+ * The queue should be emptied before calling destroy.
+ *
+ * Return 0 on success, -EPERM if queue is not empty.
+ */
+extern int cds_lfq_destroy_rcu(struct cds_lfq_queue_rcu *q);
/*
- * 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 before performing the actual memory reclamation
- * in the release primitive.
- * 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).
+ * Should be called under rcu read lock critical section.
*/
-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 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 caller must wait for a grace period to pass before freeing the returned
+ * node or modifying the cds_lfq_node_rcu structure.
+ * Returns NULL if queue is empty.
+ */
+extern
+struct cds_lfq_node_rcu *cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu *q);
+
+#endif /* !_LGPL_SOURCE */
+
+#ifdef __cplusplus
}
+#endif
#endif /* _URCU_RCULFQUEUE_H */
projects / urcu.git / blobdiff