+++ /dev/null
-#ifndef _URCU_WFQUEUE_H
-#define _URCU_WFQUEUE_H
-
-/*
- * wfqueue.h
- *
- * Userspace RCU library - Queue with Wait-Free Enqueue/Blocking Dequeue
- *
- * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * 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 <pthread.h>
-#include <assert.h>
-#include <urcu/compiler.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
-#error "Dynamic loader LGPL wrappers not implemented yet"
-#endif
-
-/*
- * Queue with wait-free enqueue/blocking dequeue.
- * This implementation adds a dummy head node when the queue is empty to ensure
- * we can always update the queue locklessly.
- *
- * Inspired from half-wait-free/half-blocking queue implementation done by
- * Paul E. McKenney.
- */
-
-struct wfq_node {
- struct wfq_node *next;
-};
-
-struct wfq_queue {
- struct wfq_node *head, **tail;
- struct wfq_node dummy; /* Dummy node */
- pthread_mutex_t lock;
-};
-
-void wfq_node_init(struct wfq_node *node)
-{
- node->next = NULL;
-}
-
-void wfq_init(struct wfq_queue *q)
-{
- int ret;
-
- wfq_node_init(&q->dummy);
- /* Set queue head and tail */
- q->head = &q->dummy;
- q->tail = &q->dummy.next;
- ret = pthread_mutex_init(&q->lock, NULL);
- assert(!ret);
-}
-
-void wfq_enqueue(struct wfq_queue *q, struct wfq_node *node)
-{
- struct wfq_node **old_tail;
-
- /*
- * uatomic_xchg() implicit memory barrier orders earlier stores to data
- * structure containing node and setting node->next to NULL before
- * publication.
- */
- old_tail = uatomic_xchg(&q->tail, node);
- /*
- * At this point, dequeuers see a NULL old_tail->next, which indicates
- * that the queue is being appended to. The following store will append
- * "node" to the queue from a dequeuer perspective.
- */
- STORE_SHARED(*old_tail, node);
-}
-
-/*
- * It is valid to reuse and free a dequeued node immediately.
- *
- * No need to go on a waitqueue here, as there is no possible state in which the
- * list could cause dequeue to busy-loop needlessly while waiting for another
- * thread to be scheduled. The queue appears empty until tail->next is set by
- * enqueue.
- */
-struct wfq_node *
-__wfq_dequeue_blocking(struct wfq_queue *q)
-{
- struct wfq_node *node, *next;
- int busy_wait = 16;
-
- /*
- * Queue is empty if it only contains the dummy node.
- */
- if (q->head == &q->dummy && LOAD_SHARED(q->tail) == &q->dummy.next)
- return NULL;
- node = q->head;
-
- /*
- * Adaptative busy-looping waiting for enqueuer to complete enqueue.
- */
- while ((next = LOAD_SHARED(node->next)) == NULL) {
- if (busy_wait > 0) {
- cpu_relax();
- busy_wait--;
- } else
- poll(NULL, 0, 1); /* Wait for 1ms */
- }
- /*
- * Move queue head forward.
- */
- q->head = next;
- /*
- * Requeue dummy node if we just dequeued it.
- */
- if (node == &q->dummy) {
- wfq_node_init(node);
- wfq_enqueue(q, node);
- return __wfq_dequeue_blocking(q);
- }
- return node;
-}
-
-struct wfq_node *
-wfq_dequeue_blocking(struct wfq_queue *q)
-{
- struct wfq_node *retnode;
- int ret;
-
- ret = pthread_mutex_lock(&q->lock);
- assert(!ret);
- retnode = __wfq_dequeue_blocking(q);
- ret = pthread_mutex_unlock(&q->lock);
- assert(!ret);
- return retnode;
-}
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* _URCU_WFQUEUE_H */
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