1 #ifndef _URCU_WFCQUEUE_H
2 #define _URCU_WFCQUEUE_H
7 * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
9 * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 * Copyright 2011-2012 - Lai Jiangshan <laijs@cn.fujitsu.com>
12 * This library is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU Lesser General Public
14 * License as published by the Free Software Foundation; either
15 * version 2.1 of the License, or (at your option) any later version.
17 * This library is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * Lesser General Public License for more details.
22 * You should have received a copy of the GNU Lesser General Public
23 * License along with this library; if not, write to the Free Software
24 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
30 #include <urcu/compiler.h>
31 #include <urcu/arch.h>
38 * Concurrent queue with wait-free enqueue/blocking dequeue.
40 * This queue has been designed and implemented collaboratively by
41 * Mathieu Desnoyers and Lai Jiangshan. Inspired from
42 * half-wait-free/half-blocking queue implementation done by Paul E.
46 struct cds_wfcq_node
{
47 struct cds_wfcq_node
*next
;
51 * Do not put head and tail on the same cache-line if concurrent
52 * enqueue/dequeue are expected from many CPUs. This eliminates
53 * false-sharing between enqueue and dequeue.
55 struct cds_wfcq_head
{
56 struct cds_wfcq_node node
;
60 struct cds_wfcq_tail
{
61 struct cds_wfcq_node
*p
;
66 #include <urcu/static/wfcqueue.h>
68 #define cds_wfcq_node_init _cds_wfcq_node_init
69 #define cds_wfcq_init _cds_wfcq_init
70 #define cds_wfcq_empty _cds_wfcq_empty
71 #define cds_wfcq_enqueue _cds_wfcq_enqueue
74 #define cds_wfcq_dequeue_lock _cds_wfcq_dequeue_lock
75 #define cds_wfcq_dequeue_unlock _cds_wfcq_dequeue_unlock
77 /* Locking performed within cds_wfcq calls. */
78 #define cds_wfcq_dequeue_blocking _cds_wfcq_dequeue_blocking
79 #define cds_wfcq_splice_blocking _cds_wfcq_splice_blocking
80 #define cds_wfcq_first_blocking _cds_wfcq_first_blocking
81 #define cds_wfcq_next_blocking _cds_wfcq_next_blocking
83 /* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */
84 #define __cds_wfcq_dequeue_blocking ___cds_wfcq_dequeue_blocking
85 #define __cds_wfcq_splice_blocking ___cds_wfcq_splice_blocking
86 #define __cds_wfcq_first_blocking ___cds_wfcq_first_blocking
87 #define __cds_wfcq_next_blocking ___cds_wfcq_next_blocking
89 #else /* !_LGPL_SOURCE */
92 * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API
94 * Unless otherwise stated, the caller must ensure mutual exclusion of
95 * queue update operations "dequeue" and "splice" (for source queue).
96 * Queue read operations "first" and "next", which are used by
97 * "for_each" iterations, need to be protected against concurrent
98 * "dequeue" and "splice" (for source queue) by the caller.
99 * "enqueue", "splice" (for destination queue), and "empty" are the only
100 * operations that can be used without any mutual exclusion.
101 * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
103 * For convenience, cds_wfcq_dequeue_blocking() and
104 * cds_wfcq_splice_blocking() hold the dequeue lock.
106 * Besides locking, mutual exclusion of dequeue, splice and iteration
107 * can be ensured by performing all of those operations from a single
108 * thread, without requiring any lock.
112 * cds_wfcq_node_init: initialize wait-free queue node.
114 extern void cds_wfcq_node_init(struct cds_wfcq_node
*node
);
117 * cds_wfcq_init: initialize wait-free queue.
119 extern void cds_wfcq_init(struct cds_wfcq_head
*head
,
120 struct cds_wfcq_tail
*tail
);
123 * cds_wfcq_empty: return whether wait-free queue is empty.
125 * No memory barrier is issued. No mutual exclusion is required.
127 extern bool cds_wfcq_empty(struct cds_wfcq_head
*head
,
128 struct cds_wfcq_tail
*tail
);
131 * cds_wfcq_dequeue_lock: take the dequeue mutual exclusion lock.
133 extern void cds_wfcq_dequeue_lock(struct cds_wfcq_head
*head
,
134 struct cds_wfcq_tail
*tail
);
137 * cds_wfcq_dequeue_unlock: release the dequeue mutual exclusion lock.
139 extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head
*head
,
140 struct cds_wfcq_tail
*tail
);
143 * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
145 * Issues a full memory barrier before enqueue. No mutual exclusion is
148 extern void cds_wfcq_enqueue(struct cds_wfcq_head
*head
,
149 struct cds_wfcq_tail
*tail
,
150 struct cds_wfcq_node
*node
);
153 * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
155 * Content written into the node before enqueue is guaranteed to be
156 * consistent, but no other memory ordering is ensured.
157 * It is valid to reuse and free a dequeued node immediately.
158 * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is
161 extern struct cds_wfcq_node
*cds_wfcq_dequeue_blocking(
162 struct cds_wfcq_head
*head
,
163 struct cds_wfcq_tail
*tail
);
166 * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
168 * Dequeue all nodes from src_q.
169 * dest_q must be already initialized.
170 * Content written into the node before enqueue is guaranteed to be
171 * consistent, but no other memory ordering is ensured.
172 * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is
175 extern void cds_wfcq_splice_blocking(
176 struct cds_wfcq_head
*dest_q_head
,
177 struct cds_wfcq_tail
*dest_q_tail
,
178 struct cds_wfcq_head
*src_q_head
,
179 struct cds_wfcq_tail
*src_q_tail
);
182 * __cds_wfcq_dequeue_blocking:
184 * Content written into the node before enqueue is guaranteed to be
185 * consistent, but no other memory ordering is ensured.
186 * It is valid to reuse and free a dequeued node immediately.
187 * Dequeue/splice/iteration mutual exclusion should be ensured by the
190 extern struct cds_wfcq_node
*__cds_wfcq_dequeue_blocking(
191 struct cds_wfcq_head
*head
,
192 struct cds_wfcq_tail
*tail
);
195 * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
197 * Dequeue all nodes from src_q.
198 * dest_q must be already initialized.
199 * Content written into the node before enqueue is guaranteed to be
200 * consistent, but no other memory ordering is ensured.
201 * Dequeue/splice/iteration mutual exclusion for src_q should be ensured
204 extern void __cds_wfcq_splice_blocking(
205 struct cds_wfcq_head
*dest_q_head
,
206 struct cds_wfcq_tail
*dest_q_tail
,
207 struct cds_wfcq_head
*src_q_head
,
208 struct cds_wfcq_tail
*src_q_tail
);
211 * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
213 * Content written into the node before enqueue is guaranteed to be
214 * consistent, but no other memory ordering is ensured.
215 * Dequeue/splice/iteration mutual exclusion should be ensured by the
218 * Used by for-like iteration macros:
219 * __cds_wfcq_for_each_blocking()
220 * __cds_wfcq_for_each_blocking_safe()
222 extern struct cds_wfcq_node
*__cds_wfcq_first_blocking(
223 struct cds_wfcq_head
*head
,
224 struct cds_wfcq_tail
*tail
);
227 * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
229 * Content written into the node before enqueue is guaranteed to be
230 * consistent, but no other memory ordering is ensured.
231 * Dequeue/splice/iteration mutual exclusion should be ensured by the
234 * Used by for-like iteration macros:
235 * __cds_wfcq_for_each_blocking()
236 * __cds_wfcq_for_each_blocking_safe()
238 extern struct cds_wfcq_node
*__cds_wfcq_next_blocking(
239 struct cds_wfcq_head
*head
,
240 struct cds_wfcq_tail
*tail
,
241 struct cds_wfcq_node
*node
);
243 #endif /* !_LGPL_SOURCE */
246 * __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue,
247 * without dequeuing them.
248 * @head: head of the queue (struct cds_wfcq_head pointer).
249 * @tail: tail of the queue (struct cds_wfcq_tail pointer).
250 * @node: iterator on the queue (struct cds_wfcq_node pointer).
252 * Content written into each node before enqueue is guaranteed to be
253 * consistent, but no other memory ordering is ensured.
254 * Dequeue/splice/iteration mutual exclusion should be ensured by the
257 #define __cds_wfcq_for_each_blocking(head, tail, node) \
258 for (node = __cds_wfcq_first_blocking(head, tail); \
260 node = __cds_wfcq_next_blocking(head, tail, node))
263 * __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue,
264 * without dequeuing them. Safe against deletion.
265 * @head: head of the queue (struct cds_wfcq_head pointer).
266 * @tail: tail of the queue (struct cds_wfcq_tail pointer).
267 * @node: iterator on the queue (struct cds_wfcq_node pointer).
268 * @n: struct cds_wfcq_node pointer holding the next pointer (used
271 * Content written into each node before enqueue is guaranteed to be
272 * consistent, but no other memory ordering is ensured.
273 * Dequeue/splice/iteration mutual exclusion should be ensured by the
276 #define __cds_wfcq_for_each_blocking_safe(head, tail, node, n) \
277 for (node = __cds_wfcq_first_blocking(head, tail), \
278 n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL); \
280 node = n, n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL))
286 #endif /* _URCU_WFCQUEUE_H */
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