1 #ifndef _URCU_WFSTACK_H
2 #define _URCU_WFSTACK_H
7 * Userspace RCU library - Stack with wait-free push, blocking traversal.
9 * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
29 #include <urcu/compiler.h>
36 * Stack with wait-free push, blocking traversal.
38 * Stack implementing push, pop, pop_all operations, as well as iterator
39 * on the stack head returned by pop_all.
41 * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
43 * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
44 * iteration on stack head returned by pop_all.
46 * Synchronization table:
48 * External synchronization techniques described in the API below is
49 * required between pairs marked with "X". No external synchronization
50 * required between pairs marked with "-".
52 * cds_wfs_push __cds_wfs_pop __cds_wfs_pop_all
55 * __cds_wfs_pop_all - X -
57 * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
61 #define CDS_WFS_WOULDBLOCK ((void *) -1UL)
64 CDS_WFS_STATE_LAST
= (1U << 0),
68 * struct cds_wfs_node is returned by __cds_wfs_pop, and also used as
69 * iterator on stack. It is not safe to dereference the node next
70 * pointer when returned by __cds_wfs_pop_blocking.
73 struct cds_wfs_node
*next
;
77 * struct cds_wfs_head is returned by __cds_wfs_pop_all, and can be used
78 * to begin iteration on the stack. "node" needs to be the first field of
79 * cds_wfs_head, so the end-of-stack pointer value can be used for both
83 struct cds_wfs_node node
;
86 struct cds_wfs_stack
{
87 struct cds_wfs_head
*head
;
93 #include <urcu/static/wfstack.h>
95 #define cds_wfs_node_init _cds_wfs_node_init
96 #define cds_wfs_init _cds_wfs_init
97 #define cds_wfs_empty _cds_wfs_empty
98 #define cds_wfs_push _cds_wfs_push
100 /* Locking performed internally */
101 #define cds_wfs_pop_blocking _cds_wfs_pop_blocking
102 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
103 #define cds_wfs_pop_all_blocking _cds_wfs_pop_all_blocking
106 * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
107 * cds_wfs_pop_all_blocking.
109 #define cds_wfs_first _cds_wfs_first
110 #define cds_wfs_next_blocking _cds_wfs_next_blocking
111 #define cds_wfs_next_nonblocking _cds_wfs_next_nonblocking
113 /* Pop locking with internal mutex */
114 #define cds_wfs_pop_lock _cds_wfs_pop_lock
115 #define cds_wfs_pop_unlock _cds_wfs_pop_unlock
117 /* Synchronization ensured by the caller. See synchronization table. */
118 #define __cds_wfs_pop_blocking ___cds_wfs_pop_blocking
119 #define __cds_wfs_pop_with_state_blocking \
120 ___cds_wfs_pop_with_state_blocking
121 #define __cds_wfs_pop_nonblocking ___cds_wfs_pop_nonblocking
122 #define __cds_wfs_pop_with_state_nonblocking \
123 ___cds_wfs_pop_with_state_nonblocking
124 #define __cds_wfs_pop_all ___cds_wfs_pop_all
126 #else /* !_LGPL_SOURCE */
129 * cds_wfs_node_init: initialize wait-free stack node.
131 extern void cds_wfs_node_init(struct cds_wfs_node
*node
);
134 * cds_wfs_init: initialize wait-free stack.
136 extern void cds_wfs_init(struct cds_wfs_stack
*s
);
139 * cds_wfs_empty: return whether wait-free stack is empty.
141 * No memory barrier is issued. No mutual exclusion is required.
143 extern bool cds_wfs_empty(struct cds_wfs_stack
*s
);
146 * cds_wfs_push: push a node into the stack.
148 * Issues a full memory barrier before push. No mutual exclusion is
151 * Returns 0 if the stack was empty prior to adding the node.
152 * Returns non-zero otherwise.
154 extern int cds_wfs_push(struct cds_wfs_stack
*s
, struct cds_wfs_node
*node
);
157 * cds_wfs_pop_blocking: pop a node from the stack.
159 * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
161 extern struct cds_wfs_node
*cds_wfs_pop_blocking(struct cds_wfs_stack
*s
);
164 * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
166 * Same as cds_wfs_pop_blocking, but stores whether the stack was
167 * empty into state (CDS_WFS_STATE_LAST).
169 extern struct cds_wfs_node
*
170 cds_wfs_pop_with_state_blocking(struct cds_wfs_stack
*s
, int *state
);
173 * cds_wfs_pop_all_blocking: pop all nodes from a stack.
175 * Calls __cds_wfs_pop_all with an internal pop mutex held.
177 extern struct cds_wfs_head
*cds_wfs_pop_all_blocking(struct cds_wfs_stack
*s
);
180 * cds_wfs_first: get first node of a popped stack.
182 * Content written into the node before enqueue is guaranteed to be
183 * consistent, but no other memory ordering is ensured.
185 * Used by for-like iteration macros in urcu/wfstack.h:
186 * cds_wfs_for_each_blocking()
187 * cds_wfs_for_each_blocking_safe()
189 * Returns NULL if popped stack is empty, top stack node otherwise.
191 extern struct cds_wfs_node
*cds_wfs_first(struct cds_wfs_head
*head
);
194 * cds_wfs_next_blocking: get next node of a popped stack.
196 * Content written into the node before enqueue is guaranteed to be
197 * consistent, but no other memory ordering is ensured.
199 * Used by for-like iteration macros in urcu/wfstack.h:
200 * cds_wfs_for_each_blocking()
201 * cds_wfs_for_each_blocking_safe()
203 * Returns NULL if reached end of popped stack, non-NULL next stack
206 extern struct cds_wfs_node
*cds_wfs_next_blocking(struct cds_wfs_node
*node
);
209 * cds_wfs_next_nonblocking: get next node of a popped stack.
211 * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
214 extern struct cds_wfs_node
*cds_wfs_next_nonblocking(struct cds_wfs_node
*node
);
217 * cds_wfs_pop_lock: lock stack pop-protection mutex.
219 extern void cds_wfs_pop_lock(struct cds_wfs_stack
*s
);
222 * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
224 extern void cds_wfs_pop_unlock(struct cds_wfs_stack
*s
);
227 * __cds_wfs_pop_blocking: pop a node from the stack.
229 * Returns NULL if stack is empty.
231 * __cds_wfs_pop_blocking needs to be synchronized using one of the
232 * following techniques:
234 * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
235 * section. The caller must wait for a grace period to pass before
236 * freeing the returned node or modifying the cds_wfs_node structure.
237 * 2) Using mutual exclusion (e.g. mutexes) to protect
238 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
239 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
240 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
242 extern struct cds_wfs_node
*__cds_wfs_pop_blocking(struct cds_wfs_stack
*s
);
245 * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
247 * Same as __cds_wfs_pop_blocking, but stores whether the stack was
248 * empty into state (CDS_WFS_STATE_LAST).
250 extern struct cds_wfs_node
*
251 __cds_wfs_pop_with_state_blocking(struct cds_wfs_stack
*s
, int *state
);
254 * __cds_wfs_pop_nonblocking: pop a node from the stack.
256 * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
259 extern struct cds_wfs_node
*__cds_wfs_pop_nonblocking(struct cds_wfs_stack
*s
);
262 * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
264 * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
265 * empty into state (CDS_WFS_STATE_LAST).
267 extern struct cds_wfs_node
*
268 __cds_wfs_pop_with_state_nonblocking(struct cds_wfs_stack
*s
,
272 * __cds_wfs_pop_all: pop all nodes from a stack.
274 * __cds_wfs_pop_all does not require any synchronization with other
275 * push, nor with other __cds_wfs_pop_all, but requires synchronization
276 * matching the technique used to synchronize __cds_wfs_pop_blocking:
278 * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
279 * section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
280 * must wait for a grace period to pass before freeing the returned
281 * node or modifying the cds_wfs_node structure. However, no RCU
282 * read-side critical section is needed around __cds_wfs_pop_all.
283 * 2) Using mutual exclusion (e.g. mutexes) to protect
284 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
285 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
286 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
288 extern struct cds_wfs_head
*__cds_wfs_pop_all(struct cds_wfs_stack
*s
);
290 #endif /* !_LGPL_SOURCE */
297 * cds_wfs_for_each_blocking: Iterate over all nodes returned by
298 * __cds_wfs_pop_all().
299 * @head: head of the queue (struct cds_wfs_head pointer).
300 * @node: iterator (struct cds_wfs_node pointer).
302 * Content written into each node before enqueue is guaranteed to be
303 * consistent, but no other memory ordering is ensured.
305 #define cds_wfs_for_each_blocking(head, node) \
306 for (node = cds_wfs_first(head); \
308 node = cds_wfs_next_blocking(node))
311 * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
312 * __cds_wfs_pop_all(). Safe against deletion.
313 * @head: head of the queue (struct cds_wfs_head pointer).
314 * @node: iterator (struct cds_wfs_node pointer).
315 * @n: struct cds_wfs_node pointer holding the next pointer (used
318 * Content written into each node before enqueue is guaranteed to be
319 * consistent, but no other memory ordering is ensured.
321 #define cds_wfs_for_each_blocking_safe(head, node, n) \
322 for (node = cds_wfs_first(head), \
323 n = (node ? cds_wfs_next_blocking(node) : NULL); \
325 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
327 #endif /* _URCU_WFSTACK_H */
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