016d9f2207df89a37cca8d7ca49847b829c8bf23
[urcu.git] / include / urcu / wfstack.h
1 #ifndef _URCU_WFSTACK_H
2 #define _URCU_WFSTACK_H
3
4 /*
5 * urcu/wfstack.h
6 *
7 * Userspace RCU library - Stack with wait-free push, blocking traversal.
8 *
9 * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 *
11 * This library is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU Lesser General Public
13 * License as published by the Free Software Foundation; either
14 * version 2.1 of the License, or (at your option) any later version.
15 *
16 * This library is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 * Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this library; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 */
25
26 #include <pthread.h>
27 #include <stdbool.h>
28 #include <urcu/compiler.h>
29
30 #ifdef __cplusplus
31 extern "C" {
32 #endif
33
34 /*
35 * Stack with wait-free push, blocking traversal.
36 *
37 * Stack implementing push, pop, pop_all operations, as well as iterator
38 * on the stack head returned by pop_all.
39 *
40 * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
41 * cds_wfs_first.
42 * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
43 * iteration on stack head returned by pop_all.
44 *
45 * Synchronization table:
46 *
47 * External synchronization techniques described in the API below is
48 * required between pairs marked with "X". No external synchronization
49 * required between pairs marked with "-".
50 *
51 * cds_wfs_push __cds_wfs_pop __cds_wfs_pop_all
52 * cds_wfs_push - - -
53 * __cds_wfs_pop - X X
54 * __cds_wfs_pop_all - X -
55 *
56 * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
57 * synchronization.
58 */
59
60 #define CDS_WFS_WOULDBLOCK ((struct cds_wfs_node *) -1UL)
61
62 enum cds_wfs_state {
63 CDS_WFS_STATE_LAST = (1U << 0),
64 };
65
66 /*
67 * struct cds_wfs_node is returned by __cds_wfs_pop, and also used as
68 * iterator on stack. It is not safe to dereference the node next
69 * pointer when returned by __cds_wfs_pop_blocking.
70 */
71 struct cds_wfs_node {
72 struct cds_wfs_node *next;
73 };
74
75 /*
76 * struct cds_wfs_head is returned by __cds_wfs_pop_all, and can be used
77 * to begin iteration on the stack. "node" needs to be the first field of
78 * cds_wfs_head, so the end-of-stack pointer value can be used for both
79 * types.
80 */
81 struct cds_wfs_head {
82 struct cds_wfs_node node;
83 };
84
85 struct __cds_wfs_stack {
86 struct cds_wfs_head *head;
87 };
88
89 struct cds_wfs_stack {
90 struct cds_wfs_head *head;
91 pthread_mutex_t lock;
92 };
93
94 /*
95 * The transparent union allows calling functions that work on both
96 * struct cds_wfs_stack and struct __cds_wfs_stack on any of those two
97 * types.
98 *
99 * Avoid complaints from clang++ not knowing this attribute.
100 */
101 typedef union {
102 struct __cds_wfs_stack *_s;
103 struct cds_wfs_stack *s;
104 } caa_c_transparent_union cds_wfs_stack_ptr_t;
105
106 #ifdef _LGPL_SOURCE
107
108 #include <urcu/static/wfstack.h>
109
110 #define cds_wfs_node_init _cds_wfs_node_init
111 #define cds_wfs_init _cds_wfs_init
112 #define cds_wfs_destroy _cds_wfs_destroy
113 #define __cds_wfs_init ___cds_wfs_init
114 #define cds_wfs_empty _cds_wfs_empty
115 #define cds_wfs_push _cds_wfs_push
116
117 /* Locking performed internally */
118 #define cds_wfs_pop_blocking _cds_wfs_pop_blocking
119 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
120 #define cds_wfs_pop_all_blocking _cds_wfs_pop_all_blocking
121
122 /*
123 * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
124 * cds_wfs_pop_all_blocking.
125 */
126 #define cds_wfs_first _cds_wfs_first
127 #define cds_wfs_next_blocking _cds_wfs_next_blocking
128 #define cds_wfs_next_nonblocking _cds_wfs_next_nonblocking
129
130 /* Pop locking with internal mutex */
131 #define cds_wfs_pop_lock _cds_wfs_pop_lock
132 #define cds_wfs_pop_unlock _cds_wfs_pop_unlock
133
134 /* Synchronization ensured by the caller. See synchronization table. */
135 #define __cds_wfs_pop_blocking ___cds_wfs_pop_blocking
136 #define __cds_wfs_pop_with_state_blocking \
137 ___cds_wfs_pop_with_state_blocking
138 #define __cds_wfs_pop_nonblocking ___cds_wfs_pop_nonblocking
139 #define __cds_wfs_pop_with_state_nonblocking \
140 ___cds_wfs_pop_with_state_nonblocking
141 #define __cds_wfs_pop_all ___cds_wfs_pop_all
142
143 #else /* !_LGPL_SOURCE */
144
145 /*
146 * cds_wfs_node_init: initialize wait-free stack node.
147 */
148 extern void cds_wfs_node_init(struct cds_wfs_node *node);
149
150 /*
151 * cds_wfs_init: initialize wait-free stack (with lock). Pair with
152 * cds_wfs_destroy().
153 */
154 extern void cds_wfs_init(struct cds_wfs_stack *s);
155
156 /*
157 * cds_wfs_destroy: destroy wait-free stack (with lock). Pair with
158 * cds_wfs_init().
159 */
160 extern void cds_wfs_destroy(struct cds_wfs_stack *s);
161
162 /*
163 * __cds_wfs_init: initialize wait-free stack (no lock). Don't pair with
164 * any destroy function.
165 */
166 extern void __cds_wfs_init(struct __cds_wfs_stack *s);
167
168 /*
169 * cds_wfs_empty: return whether wait-free stack is empty.
170 *
171 * No memory barrier is issued. No mutual exclusion is required.
172 */
173 extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack);
174
175 /*
176 * cds_wfs_push: push a node into the stack.
177 *
178 * Issues a full memory barrier before push. No mutual exclusion is
179 * required.
180 *
181 * Returns 0 if the stack was empty prior to adding the node.
182 * Returns non-zero otherwise.
183 */
184 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node);
185
186 /*
187 * cds_wfs_pop_blocking: pop a node from the stack.
188 *
189 * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
190 */
191 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
192
193 /*
194 * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
195 *
196 * Same as cds_wfs_pop_blocking, but stores whether the stack was
197 * empty into state (CDS_WFS_STATE_LAST).
198 */
199 extern struct cds_wfs_node *
200 cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
201
202 /*
203 * cds_wfs_pop_all_blocking: pop all nodes from a stack.
204 *
205 * Calls __cds_wfs_pop_all with an internal pop mutex held.
206 */
207 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
208
209 /*
210 * cds_wfs_first: get first node of a popped stack.
211 *
212 * Content written into the node before enqueue is guaranteed to be
213 * consistent, but no other memory ordering is ensured.
214 *
215 * Used by for-like iteration macros in urcu/wfstack.h:
216 * cds_wfs_for_each_blocking()
217 * cds_wfs_for_each_blocking_safe()
218 *
219 * Returns NULL if popped stack is empty, top stack node otherwise.
220 */
221 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
222
223 /*
224 * cds_wfs_next_blocking: get next node of a popped stack.
225 *
226 * Content written into the node before enqueue is guaranteed to be
227 * consistent, but no other memory ordering is ensured.
228 *
229 * Used by for-like iteration macros in urcu/wfstack.h:
230 * cds_wfs_for_each_blocking()
231 * cds_wfs_for_each_blocking_safe()
232 *
233 * Returns NULL if reached end of popped stack, non-NULL next stack
234 * node otherwise.
235 */
236 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
237
238 /*
239 * cds_wfs_next_nonblocking: get next node of a popped stack.
240 *
241 * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
242 * needs to block.
243 */
244 extern struct cds_wfs_node *cds_wfs_next_nonblocking(struct cds_wfs_node *node);
245
246 /*
247 * cds_wfs_pop_lock: lock stack pop-protection mutex.
248 */
249 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
250
251 /*
252 * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
253 */
254 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
255
256 /*
257 * __cds_wfs_pop_blocking: pop a node from the stack.
258 *
259 * Returns NULL if stack is empty.
260 *
261 * __cds_wfs_pop_blocking needs to be synchronized using one of the
262 * following techniques:
263 *
264 * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
265 * section. The caller must wait for a grace period to pass before
266 * freeing the returned node or modifying the cds_wfs_node structure.
267 * 2) Using mutual exclusion (e.g. mutexes) to protect
268 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
269 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
270 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
271 */
272 extern struct cds_wfs_node *__cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack);
273
274 /*
275 * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
276 *
277 * Same as __cds_wfs_pop_blocking, but stores whether the stack was
278 * empty into state (CDS_WFS_STATE_LAST).
279 */
280 extern struct cds_wfs_node *
281 __cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack,
282 int *state);
283
284 /*
285 * __cds_wfs_pop_nonblocking: pop a node from the stack.
286 *
287 * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
288 * it needs to block.
289 */
290 extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack);
291
292 /*
293 * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
294 *
295 * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
296 * empty into state (CDS_WFS_STATE_LAST).
297 */
298 extern struct cds_wfs_node *
299 __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack,
300 int *state);
301
302 /*
303 * __cds_wfs_pop_all: pop all nodes from a stack.
304 *
305 * __cds_wfs_pop_all does not require any synchronization with other
306 * push, nor with other __cds_wfs_pop_all, but requires synchronization
307 * matching the technique used to synchronize __cds_wfs_pop_blocking:
308 *
309 * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
310 * section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
311 * must wait for a grace period to pass before freeing the returned
312 * node or modifying the cds_wfs_node structure. However, no RCU
313 * read-side critical section is needed around __cds_wfs_pop_all.
314 * 2) Using mutual exclusion (e.g. mutexes) to protect
315 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
316 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
317 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
318 */
319 extern struct cds_wfs_head *__cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack);
320
321 #endif /* !_LGPL_SOURCE */
322
323 #ifdef __cplusplus
324 }
325 #endif
326
327 /*
328 * cds_wfs_for_each_blocking: Iterate over all nodes returned by
329 * __cds_wfs_pop_all().
330 * @head: head of the queue (struct cds_wfs_head pointer).
331 * @node: iterator (struct cds_wfs_node pointer).
332 *
333 * Content written into each node before enqueue is guaranteed to be
334 * consistent, but no other memory ordering is ensured.
335 */
336 #define cds_wfs_for_each_blocking(head, node) \
337 for (node = cds_wfs_first(head); \
338 node != NULL; \
339 node = cds_wfs_next_blocking(node))
340
341 /*
342 * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
343 * __cds_wfs_pop_all(). Safe against deletion.
344 * @head: head of the queue (struct cds_wfs_head pointer).
345 * @node: iterator (struct cds_wfs_node pointer).
346 * @n: struct cds_wfs_node pointer holding the next pointer (used
347 * internally).
348 *
349 * Content written into each node before enqueue is guaranteed to be
350 * consistent, but no other memory ordering is ensured.
351 */
352 #define cds_wfs_for_each_blocking_safe(head, node, n) \
353 for (node = cds_wfs_first(head), \
354 n = (node ? cds_wfs_next_blocking(node) : NULL); \
355 node != NULL; \
356 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
357
358 #endif /* _URCU_WFSTACK_H */
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