ec86032dd4e091155c64b8d80a0525874d90269a
[urcu.git] / urcu / wfcqueue.h
1 #ifndef _URCU_WFCQUEUE_H
2 #define _URCU_WFCQUEUE_H
3
4 /*
5 * urcu/wfcqueue.h
6 *
7 * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
8 *
9 * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 * Copyright 2011-2012 - Lai Jiangshan <laijs@cn.fujitsu.com>
11 *
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.
16 *
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.
21 *
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
25 */
26
27 #include <pthread.h>
28 #include <assert.h>
29 #include <stdbool.h>
30 #include <urcu/compiler.h>
31 #include <urcu/arch.h>
32
33 #ifdef __cplusplus
34 extern "C" {
35 #endif
36
37 /*
38 * Concurrent queue with wait-free enqueue/blocking dequeue.
39 *
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.
43 * McKenney.
44 */
45
46 #define CDS_WFCQ_WOULDBLOCK ((struct cds_wfcq_node *) -1UL)
47
48 enum cds_wfcq_ret {
49 CDS_WFCQ_RET_WOULDBLOCK = -1,
50 CDS_WFCQ_RET_DEST_EMPTY = 0,
51 CDS_WFCQ_RET_DEST_NON_EMPTY = 1,
52 CDS_WFCQ_RET_SRC_EMPTY = 2,
53 };
54
55 enum cds_wfcq_state {
56 CDS_WFCQ_STATE_LAST = (1U << 0),
57 };
58
59 struct cds_wfcq_node {
60 struct cds_wfcq_node *next;
61 };
62
63 /*
64 * Do not put head and tail on the same cache-line if concurrent
65 * enqueue/dequeue are expected from many CPUs. This eliminates
66 * false-sharing between enqueue and dequeue.
67 */
68 struct __cds_wfcq_head {
69 struct cds_wfcq_node node;
70 };
71
72 struct cds_wfcq_head {
73 struct cds_wfcq_node node;
74 pthread_mutex_t lock;
75 };
76
77 #ifndef __cplusplus
78 /*
79 * The transparent union allows calling functions that work on both
80 * struct cds_wfcq_head and struct __cds_wfcq_head on any of those two
81 * types.
82 */
83 typedef union {
84 struct __cds_wfcq_head *_h;
85 struct cds_wfcq_head *h;
86 } __attribute__((__transparent_union__)) cds_wfcq_head_ptr_t;
87
88 /*
89 * This static inline is only present for compatibility with C++. It is
90 * effect-less in C.
91 */
92 static inline struct __cds_wfcq_head *__cds_wfcq_head_cast(struct __cds_wfcq_head *head)
93 {
94 return head;
95 }
96
97 /*
98 * This static inline is only present for compatibility with C++. It is
99 * effect-less in C.
100 */
101 static inline struct cds_wfcq_head *cds_wfcq_head_cast(struct cds_wfcq_head *head)
102 {
103 return head;
104 }
105 #else /* #ifndef __cplusplus */
106
107 /* C++ ignores transparent union. */
108 typedef union {
109 struct __cds_wfcq_head *_h;
110 struct cds_wfcq_head *h;
111 } cds_wfcq_head_ptr_t;
112
113 /* C++ ignores transparent union. Requires an explicit conversion. */
114 static inline cds_wfcq_head_ptr_t __cds_wfcq_head_cast(struct __cds_wfcq_head *head)
115 {
116 cds_wfcq_head_ptr_t ret = { ._h = head };
117 return ret;
118 }
119 /* C++ ignores transparent union. Requires an explicit conversion. */
120 static inline cds_wfcq_head_ptr_t cds_wfcq_head_cast(struct cds_wfcq_head *head)
121 {
122 cds_wfcq_head_ptr_t ret = { .h = head };
123 return ret;
124 }
125 #endif /* #else #ifndef __cplusplus */
126
127 struct cds_wfcq_tail {
128 struct cds_wfcq_node *p;
129 };
130
131 #ifdef _LGPL_SOURCE
132
133 #include <urcu/static/wfcqueue.h>
134
135 #define cds_wfcq_node_init _cds_wfcq_node_init
136 #define cds_wfcq_init _cds_wfcq_init
137 #define cds_wfcq_empty _cds_wfcq_empty
138 #define cds_wfcq_enqueue _cds_wfcq_enqueue
139
140 /* Dequeue locking */
141 #define cds_wfcq_dequeue_lock _cds_wfcq_dequeue_lock
142 #define cds_wfcq_dequeue_unlock _cds_wfcq_dequeue_unlock
143
144 /* Locking performed within cds_wfcq calls. */
145 #define cds_wfcq_dequeue_blocking _cds_wfcq_dequeue_blocking
146 #define cds_wfcq_dequeue_with_state_blocking \
147 _cds_wfcq_dequeue_with_state_blocking
148 #define cds_wfcq_splice_blocking _cds_wfcq_splice_blocking
149 #define cds_wfcq_first_blocking _cds_wfcq_first_blocking
150 #define cds_wfcq_next_blocking _cds_wfcq_next_blocking
151
152 /* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */
153 #define __cds_wfcq_dequeue_blocking ___cds_wfcq_dequeue_blocking
154 #define __cds_wfcq_dequeue_with_state_blocking \
155 ___cds_wfcq_dequeue_with_state_blocking
156 #define __cds_wfcq_splice_blocking ___cds_wfcq_splice_blocking
157 #define __cds_wfcq_first_blocking ___cds_wfcq_first_blocking
158 #define __cds_wfcq_next_blocking ___cds_wfcq_next_blocking
159
160 /*
161 * Locking ensured by caller by holding cds_wfcq_dequeue_lock().
162 * Non-blocking: deque, first, next return CDS_WFCQ_WOULDBLOCK if they
163 * need to block. splice returns nonzero if it needs to block.
164 */
165 #define __cds_wfcq_dequeue_nonblocking ___cds_wfcq_dequeue_nonblocking
166 #define __cds_wfcq_dequeue_with_state_nonblocking \
167 ___cds_wfcq_dequeue_with_state_nonblocking
168 #define __cds_wfcq_splice_nonblocking ___cds_wfcq_splice_nonblocking
169 #define __cds_wfcq_first_nonblocking ___cds_wfcq_first_nonblocking
170 #define __cds_wfcq_next_nonblocking ___cds_wfcq_next_nonblocking
171
172 #else /* !_LGPL_SOURCE */
173
174 /*
175 * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API
176 *
177 * Synchronization table:
178 *
179 * External synchronization techniques described in the API below is
180 * required between pairs marked with "X". No external synchronization
181 * required between pairs marked with "-".
182 *
183 * Legend:
184 * [1] cds_wfcq_enqueue
185 * [2] __cds_wfcq_splice (destination queue)
186 * [3] __cds_wfcq_dequeue
187 * [4] __cds_wfcq_splice (source queue)
188 * [5] __cds_wfcq_first
189 * [6] __cds_wfcq_next
190 *
191 * [1] [2] [3] [4] [5] [6]
192 * [1] - - - - - -
193 * [2] - - - - - -
194 * [3] - - X X X X
195 * [4] - - X - X X
196 * [5] - - X X - -
197 * [6] - - X X - -
198 *
199 * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
200 *
201 * For convenience, cds_wfcq_dequeue_blocking() and
202 * cds_wfcq_splice_blocking() hold the dequeue lock.
203 *
204 * Besides locking, mutual exclusion of dequeue, splice and iteration
205 * can be ensured by performing all of those operations from a single
206 * thread, without requiring any lock.
207 */
208
209 /*
210 * cds_wfcq_node_init: initialize wait-free queue node.
211 */
212 extern void cds_wfcq_node_init(struct cds_wfcq_node *node);
213
214 /*
215 * cds_wfcq_init: initialize wait-free queue.
216 */
217 extern void cds_wfcq_init(struct cds_wfcq_head *head,
218 struct cds_wfcq_tail *tail);
219
220 /*
221 * __cds_wfcq_init: initialize wait-free queue.
222 */
223 extern void __cds_wfcq_init(struct __cds_wfcq_head *head,
224 struct cds_wfcq_tail *tail);
225
226 /*
227 * cds_wfcq_empty: return whether wait-free queue is empty.
228 *
229 * No memory barrier is issued. No mutual exclusion is required.
230 */
231 extern bool cds_wfcq_empty(cds_wfcq_head_ptr_t head,
232 struct cds_wfcq_tail *tail);
233
234 /*
235 * cds_wfcq_dequeue_lock: take the dequeue mutual exclusion lock.
236 */
237 extern void cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
238 struct cds_wfcq_tail *tail);
239
240 /*
241 * cds_wfcq_dequeue_unlock: release the dequeue mutual exclusion lock.
242 */
243 extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
244 struct cds_wfcq_tail *tail);
245
246 /*
247 * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
248 *
249 * Issues a full memory barrier before enqueue. No mutual exclusion is
250 * required.
251 *
252 * Returns false if the queue was empty prior to adding the node.
253 * Returns true otherwise.
254 */
255 extern bool cds_wfcq_enqueue(cds_wfcq_head_ptr_t head,
256 struct cds_wfcq_tail *tail,
257 struct cds_wfcq_node *node);
258
259 /*
260 * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
261 *
262 * Content written into the node before enqueue is guaranteed to be
263 * consistent, but no other memory ordering is ensured.
264 * It is valid to reuse and free a dequeued node immediately.
265 * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is
266 * ensured.
267 */
268 extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
269 struct cds_wfcq_head *head,
270 struct cds_wfcq_tail *tail);
271
272 /*
273 * cds_wfcq_dequeue_with_state_blocking: dequeue with state.
274 *
275 * Same as cds_wfcq_dequeue_blocking, but saves whether dequeueing the
276 * last node of the queue into state (CDS_WFCQ_STATE_LAST).
277 */
278 extern struct cds_wfcq_node *cds_wfcq_dequeue_with_state_blocking(
279 struct cds_wfcq_head *head,
280 struct cds_wfcq_tail *tail,
281 int *state);
282
283 /*
284 * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
285 *
286 * Dequeue all nodes from src_q.
287 * dest_q must be already initialized.
288 * Content written into the node before enqueue is guaranteed to be
289 * consistent, but no other memory ordering is ensured.
290 * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is
291 * ensured.
292 *
293 * Returns enum cds_wfcq_ret which indicates the state of the src or
294 * dest queue.
295 */
296 extern enum cds_wfcq_ret cds_wfcq_splice_blocking(
297 struct cds_wfcq_head *dest_q_head,
298 struct cds_wfcq_tail *dest_q_tail,
299 struct cds_wfcq_head *src_q_head,
300 struct cds_wfcq_tail *src_q_tail);
301
302 /*
303 * __cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
304 *
305 * Content written into the node before enqueue is guaranteed to be
306 * consistent, but no other memory ordering is ensured.
307 * It is valid to reuse and free a dequeued node immediately.
308 * Dequeue/splice/iteration mutual exclusion should be ensured by the
309 * caller.
310 */
311 extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
312 cds_wfcq_head_ptr_t head,
313 struct cds_wfcq_tail *tail);
314
315 /*
316 * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
317 *
318 * Same as __cds_wfcq_dequeue_blocking, but saves whether dequeueing the
319 * last node of the queue into state (CDS_WFCQ_STATE_LAST).
320 */
321 extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_blocking(
322 cds_wfcq_head_ptr_t head,
323 struct cds_wfcq_tail *tail,
324 int *state);
325
326 /*
327 * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
328 *
329 * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK
330 * if it needs to block.
331 */
332 extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
333 cds_wfcq_head_ptr_t head,
334 struct cds_wfcq_tail *tail);
335
336 /*
337 * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
338 *
339 * Same as __cds_wfcq_dequeue_nonblocking, but saves whether dequeueing
340 * the last node of the queue into state (CDS_WFCQ_STATE_LAST).
341 */
342 extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_nonblocking(
343 cds_wfcq_head_ptr_t head,
344 struct cds_wfcq_tail *tail,
345 int *state);
346
347 /*
348 * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
349 *
350 * Dequeue all nodes from src_q.
351 * dest_q must be already initialized.
352 * Mutual exclusion for src_q should be ensured by the caller as
353 * specified in the "Synchronisation table".
354 * Returns enum cds_wfcq_ret which indicates the state of the src or
355 * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK.
356 */
357 extern enum cds_wfcq_ret __cds_wfcq_splice_blocking(
358 cds_wfcq_head_ptr_t dest_q_head,
359 struct cds_wfcq_tail *dest_q_tail,
360 cds_wfcq_head_ptr_t src_q_head,
361 struct cds_wfcq_tail *src_q_tail);
362
363 /*
364 * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q.
365 *
366 * Same as __cds_wfcq_splice_blocking, but returns
367 * CDS_WFCQ_RET_WOULDBLOCK if it needs to block.
368 */
369 extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking(
370 cds_wfcq_head_ptr_t dest_q_head,
371 struct cds_wfcq_tail *dest_q_tail,
372 cds_wfcq_head_ptr_t src_q_head,
373 struct cds_wfcq_tail *src_q_tail);
374
375 /*
376 * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
377 *
378 * Content written into the node before enqueue is guaranteed to be
379 * consistent, but no other memory ordering is ensured.
380 * Dequeue/splice/iteration mutual exclusion should be ensured by the
381 * caller.
382 *
383 * Used by for-like iteration macros:
384 * __cds_wfcq_for_each_blocking()
385 * __cds_wfcq_for_each_blocking_safe()
386 *
387 * Returns NULL if queue is empty, first node otherwise.
388 */
389 extern struct cds_wfcq_node *__cds_wfcq_first_blocking(
390 cds_wfcq_head_ptr_t head,
391 struct cds_wfcq_tail *tail);
392
393 /*
394 * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing.
395 *
396 * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if
397 * it needs to block.
398 */
399 extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking(
400 cds_wfcq_head_ptr_t head,
401 struct cds_wfcq_tail *tail);
402
403 /*
404 * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
405 *
406 * Content written into the node before enqueue is guaranteed to be
407 * consistent, but no other memory ordering is ensured.
408 * Dequeue/splice/iteration mutual exclusion should be ensured by the
409 * caller.
410 *
411 * Used by for-like iteration macros:
412 * __cds_wfcq_for_each_blocking()
413 * __cds_wfcq_for_each_blocking_safe()
414 *
415 * Returns NULL if reached end of queue, non-NULL next queue node
416 * otherwise.
417 */
418 extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
419 cds_wfcq_head_ptr_t head,
420 struct cds_wfcq_tail *tail,
421 struct cds_wfcq_node *node);
422
423 /*
424 * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
425 *
426 * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if
427 * it needs to block.
428 */
429 extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking(
430 cds_wfcq_head_ptr_t head,
431 struct cds_wfcq_tail *tail,
432 struct cds_wfcq_node *node);
433
434 #endif /* !_LGPL_SOURCE */
435
436 /*
437 * __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue,
438 * without dequeuing them.
439 * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer).
440 * @tail: tail of the queue (struct cds_wfcq_tail pointer).
441 * @node: iterator on the queue (struct cds_wfcq_node pointer).
442 *
443 * Content written into each node before enqueue is guaranteed to be
444 * consistent, but no other memory ordering is ensured.
445 * Dequeue/splice/iteration mutual exclusion should be ensured by the
446 * caller.
447 */
448 #define __cds_wfcq_for_each_blocking(head, tail, node) \
449 for (node = __cds_wfcq_first_blocking(head, tail); \
450 node != NULL; \
451 node = __cds_wfcq_next_blocking(head, tail, node))
452
453 /*
454 * __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue,
455 * without dequeuing them. Safe against deletion.
456 * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer).
457 * @tail: tail of the queue (struct cds_wfcq_tail pointer).
458 * @node: iterator on the queue (struct cds_wfcq_node pointer).
459 * @n: struct cds_wfcq_node pointer holding the next pointer (used
460 * internally).
461 *
462 * Content written into each node before enqueue is guaranteed to be
463 * consistent, but no other memory ordering is ensured.
464 * Dequeue/splice/iteration mutual exclusion should be ensured by the
465 * caller.
466 */
467 #define __cds_wfcq_for_each_blocking_safe(head, tail, node, n) \
468 for (node = __cds_wfcq_first_blocking(head, tail), \
469 n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL); \
470 node != NULL; \
471 node = n, n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL))
472
473 #ifdef __cplusplus
474 }
475 #endif
476
477 #endif /* _URCU_WFCQUEUE_H */
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