+++ /dev/null
-#ifndef _URCU_WFCQUEUE_STATIC_H
-#define _URCU_WFCQUEUE_STATIC_H
-
-/*
- * wfcqueue-static.h
- *
- * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
- *
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See wfcqueue.h for linking
- * dynamically with the userspace rcu library.
- *
- * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- * Copyright 2011-2012 - Lai Jiangshan <laijs@cn.fujitsu.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 <poll.h>
-#include <stdbool.h>
-#include <urcu/compiler.h>
-#include <urcu/uatomic.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/*
- * Concurrent queue with wait-free enqueue/blocking dequeue.
- *
- * Inspired from half-wait-free/half-blocking queue implementation done by
- * Paul E. McKenney.
- *
- * Mutual exclusion of __cds_wfcq_* API
- *
- * Unless otherwise stated, the caller must ensure mutual exclusion of
- * queue update operations "dequeue" and "splice" (for source queue).
- * Queue read operations "first" and "next" need to be protected against
- * concurrent "dequeue" and "splice" (for source queue) by the caller.
- * "enqueue", "splice" (for destination queue), and "empty" are the only
- * operations that can be used without any mutual exclusion.
- * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
- *
- * For convenience, cds_wfcq_dequeue_blocking() and
- * cds_wfcq_splice_blocking() hold the dequeue lock.
- */
-
-#define WFCQ_ADAPT_ATTEMPTS 10 /* Retry if being set */
-#define WFCQ_WAIT 10 /* Wait 10 ms if being set */
-
-/*
- * cds_wfcq_node_init: initialize wait-free queue node.
- */
-static inline void _cds_wfcq_node_init(struct cds_wfcq_node *node)
-{
- node->next = NULL;
-}
-
-/*
- * cds_wfcq_init: initialize wait-free queue.
- */
-static inline void _cds_wfcq_init(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
-{
- int ret;
-
- /* Set queue head and tail */
- _cds_wfcq_node_init(&head->node);
- tail->p = &head->node;
- ret = pthread_mutex_init(&head->lock, NULL);
- assert(!ret);
-}
-
-/*
- * cds_wfcq_empty: return whether wait-free queue is empty.
- *
- * No memory barrier is issued. No mutual exclusion is required.
- */
-static inline bool _cds_wfcq_empty(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
-{
- /*
- * Queue is empty if no node is pointed by head->node.next nor
- * tail->p. Even though the tail->p check is sufficient to find
- * out of the queue is empty, we first check head->node.next as a
- * common case to ensure that dequeuers do not frequently access
- * enqueuer's tail->p cache line.
- */
- return CMM_LOAD_SHARED(head->node.next) == NULL
- && CMM_LOAD_SHARED(tail->p) == &head->node;
-}
-
-static inline void _cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
-{
- int ret;
-
- ret = pthread_mutex_lock(&head->lock);
- assert(!ret);
-}
-
-static inline void _cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
-{
- int ret;
-
- ret = pthread_mutex_unlock(&head->lock);
- assert(!ret);
-}
-
-static inline void ___cds_wfcq_append(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail,
- struct cds_wfcq_node *new_head,
- struct cds_wfcq_node *new_tail)
-{
- struct cds_wfcq_node *old_tail;
-
- /*
- * Implicit memory barrier before uatomic_xchg() orders earlier
- * stores to data structure containing node and setting
- * node->next to NULL before publication.
- */
- old_tail = uatomic_xchg(&tail->p, new_tail);
-
- /*
- * Implicit memory barrier after uatomic_xchg() orders store to
- * q->tail before store to old_tail->next.
- *
- * At this point, dequeuers see a NULL tail->p->next, which
- * indicates that the queue is being appended to. The following
- * store will append "node" to the queue from a dequeuer
- * perspective.
- */
- CMM_STORE_SHARED(old_tail->next, new_head);
-}
-
-/*
- * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
- *
- * Issues a full memory barrier before enqueue. No mutual exclusion is
- * required.
- */
-static inline void _cds_wfcq_enqueue(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail,
- struct cds_wfcq_node *new_tail)
-{
- ___cds_wfcq_append(head, tail, new_tail, new_tail);
-}
-
-/*
- * Waiting for enqueuer to complete enqueue and return the next node.
- */
-static inline struct cds_wfcq_node *
-___cds_wfcq_node_sync_next(struct cds_wfcq_node *node)
-{
- struct cds_wfcq_node *next;
- int attempt = 0;
-
- /*
- * Adaptative busy-looping waiting for enqueuer to complete enqueue.
- */
- while ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
- if (++attempt >= WFCQ_ADAPT_ATTEMPTS) {
- poll(NULL, 0, WFCQ_WAIT); /* Wait for 10ms */
- attempt = 0;
- } else {
- caa_cpu_relax();
- }
- }
-
- return next;
-}
-
-/*
- * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
- *
- * Content written into the node before enqueue is guaranteed to be
- * consistent, but no other memory ordering is ensured.
- * Should be called with cds_wfcq_dequeue_lock() held.
- */
-static inline struct cds_wfcq_node *
-___cds_wfcq_first_blocking(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
-{
- struct cds_wfcq_node *node;
-
- if (_cds_wfcq_empty(head, tail))
- return NULL;
- node = ___cds_wfcq_node_sync_next(&head->node);
- /* Load head->node.next before loading node's content */
- cmm_smp_read_barrier_depends();
- return node;
-}
-
-/*
- * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
- *
- * Content written into the node before enqueue is guaranteed to be
- * consistent, but no other memory ordering is ensured.
- * Should be called with cds_wfcq_dequeue_lock() held.
- */
-static inline struct cds_wfcq_node *
-___cds_wfcq_next_blocking(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail,
- struct cds_wfcq_node *node)
-{
- struct cds_wfcq_node *next;
-
- /*
- * Even though the following tail->p check is sufficient to find
- * out if we reached the end of the queue, we first check
- * node->next as a common case to ensure that iteration on nodes
- * do not frequently access enqueuer's tail->p cache line.
- */
- if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
- /* Load node->next before tail->p */
- cmm_smp_rmb();
- if (CMM_LOAD_SHARED(tail->p) == node)
- return NULL;
- next = ___cds_wfcq_node_sync_next(node);
- }
- /* Load node->next before loading next's content */
- cmm_smp_read_barrier_depends();
- return next;
-}
-
-/*
- * __cds_wfcq_dequeue_blocking: dequeue a node from the queue.
- *
- * 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.
- *
- * Content written into the node before enqueue is guaranteed to be
- * consistent, but no other memory ordering is ensured.
- * It is valid to reuse and free a dequeued node immediately.
- * Should be called with cds_wfcq_dequeue_lock() held.
- */
-static inline struct cds_wfcq_node *
-___cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
-{
- struct cds_wfcq_node *node, *next;
-
- if (_cds_wfcq_empty(head, tail))
- return NULL;
-
- node = ___cds_wfcq_node_sync_next(&head->node);
-
- if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
- /*
- * @node is probably the only node in the queue.
- * Try to move the tail to &q->head.
- * q->head.next is set to NULL here, and stays
- * NULL if the cmpxchg succeeds. Should the
- * cmpxchg fail due to a concurrent enqueue, the
- * q->head.next will be set to the next node.
- * The implicit memory barrier before
- * uatomic_cmpxchg() orders load node->next
- * before loading q->tail.
- * The implicit memory barrier before uatomic_cmpxchg
- * orders load q->head.next before loading node's
- * content.
- */
- _cds_wfcq_node_init(&head->node);
- if (uatomic_cmpxchg(&tail->p, node, &head->node) == node)
- return node;
- next = ___cds_wfcq_node_sync_next(node);
- }
-
- /*
- * Move queue head forward.
- */
- head->node.next = next;
-
- /* Load q->head.next before loading node's content */
- cmm_smp_read_barrier_depends();
- return node;
-}
-
-/*
- * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
- *
- * Dequeue all nodes from src_q.
- * dest_q must be already initialized.
- * Should be called with cds_wfcq_dequeue_lock() held on src_q.
- */
-static inline void
-___cds_wfcq_splice_blocking(
- struct cds_wfcq_head *dest_q_head,
- struct cds_wfcq_tail *dest_q_tail,
- struct cds_wfcq_head *src_q_head,
- struct cds_wfcq_tail *src_q_tail)
-{
- struct cds_wfcq_node *head, *tail;
-
- if (_cds_wfcq_empty(src_q_head, src_q_tail))
- return;
-
- head = ___cds_wfcq_node_sync_next(&src_q_head->node);
- _cds_wfcq_node_init(&src_q_head->node);
-
- /*
- * Memory barrier implied before uatomic_xchg() orders store to
- * src_q->head before store to src_q->tail. This is required by
- * concurrent enqueue on src_q, which exchanges the tail before
- * updating the previous tail's next pointer.
- */
- tail = uatomic_xchg(&src_q_tail->p, &src_q_head->node);
-
- /*
- * Append the spliced content of src_q into dest_q. Does not
- * require mutual exclusion on dest_q (wait-free).
- */
- ___cds_wfcq_append(dest_q_head, dest_q_tail, head, tail);
-}
-
-/*
- * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
- *
- * Content written into the node before enqueue is guaranteed to be
- * consistent, but no other memory ordering is ensured.
- * Mutual exlusion with (and only with) cds_wfcq_splice_blocking is
- * ensured.
- * It is valid to reuse and free a dequeued node immediately.
- */
-static inline struct cds_wfcq_node *
-_cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
-{
- struct cds_wfcq_node *retval;
-
- _cds_wfcq_dequeue_lock(head, tail);
- retval = ___cds_wfcq_dequeue_blocking(head, tail);
- _cds_wfcq_dequeue_unlock(head, tail);
- return retval;
-}
-
-/*
- * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
- *
- * Dequeue all nodes from src_q.
- * dest_q must be already initialized.
- * Content written into the node before enqueue is guaranteed to be
- * consistent, but no other memory ordering is ensured.
- * Mutual exlusion with (and only with) cds_wfcq_dequeue_blocking is
- * ensured.
- */
-static inline void
-_cds_wfcq_splice_blocking(
- struct cds_wfcq_head *dest_q_head,
- struct cds_wfcq_tail *dest_q_tail,
- struct cds_wfcq_head *src_q_head,
- struct cds_wfcq_tail *src_q_tail)
-{
- _cds_wfcq_dequeue_lock(src_q_head, src_q_tail);
- ___cds_wfcq_splice_blocking(dest_q_head, dest_q_tail,
- src_q_head, src_q_tail);
- _cds_wfcq_dequeue_unlock(src_q_head, src_q_tail);
-}
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* _URCU_WFCQUEUE_STATIC_H */
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