+++ /dev/null
-#ifndef _URCU_RCULFQUEUE_STATIC_H
-#define _URCU_RCULFQUEUE_STATIC_H
-
-/*
- * rculfqueue-static.h
- *
- * Userspace RCU library - Lock-Free RCU Queue
- *
- * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See rculfqueue.h for linking
- * dynamically with the userspace rcu library.
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- */
-
-#include <urcu/urcu_ref.h>
-#include <urcu/uatomic_arch.h>
-#include <assert.h>
-/* A urcu implementation header should be already included. */
-
-#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
-
-void _cds_lfq_node_init_rcu(struct cds_lfq_node_rcu *node)
-{
- node->next = NULL;
- urcu_ref_init(&node->ref);
-}
-
-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;
-}
-
-/*
- * 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
- * node before publication.
- */
-
- for (;;) {
- struct cds_lfq_node_rcu *tail, *next;
-
- 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).
- */
- (void) uatomic_cmpxchg(&q->tail, tail, node);
- return;
- } else {
- /*
- * Failure to append to current tail. Help moving tail
- * further and retry.
- */
- (void) uatomic_cmpxchg(&q->tail, tail, next);
- continue;
- }
- }
-}
-
-/*
- * 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.
- */
-struct cds_lfq_node_rcu *_cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu *q)
-{
- for (;;) {
- struct cds_lfq_node_rcu *head, *next;
-
- head = rcu_dereference(q->head);
- next = rcu_dereference(head->next);
- if (next) {
- if (uatomic_cmpxchg(&q->head, head, next) == head) {
- urcu_ref_put(&head->ref, q->release);
- return next;
- } else {
- /* Concurrently pushed, retry */
- continue;
- }
- } else {
- /* Empty */
- return NULL;
- }
- }
-}
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* _URCU_RCULFQUEUE_STATIC_H */
projects / urcu.git / blobdiff