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
28 #include <urcu/compiler.h>
35 * Stack with wait-free push, blocking traversal.
37 * Stack implementing push, pop, pop_all operations, as well as iterator
38 * on the stack head returned by pop_all.
40 * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
42 * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
43 * iteration on stack head returned by pop_all.
45 * Synchronization table:
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 "-".
51 * cds_wfs_push __cds_wfs_pop __cds_wfs_pop_all
54 * __cds_wfs_pop_all - X -
56 * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
60 #define CDS_WFS_WOULDBLOCK ((struct cds_wfs_node *) -1UL)
63 CDS_WFS_STATE_LAST
= (1U << 0),
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.
72 struct cds_wfs_node
*next
;
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
82 struct cds_wfs_node node
;
85 struct __cds_wfs_stack
{
86 struct cds_wfs_head
*head
;
89 struct cds_wfs_stack
{
90 struct cds_wfs_head
*head
;
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
99 * Avoid complaints from clang++ not knowing this attribute.
102 struct __cds_wfs_stack
*_s
;
103 struct cds_wfs_stack
*s
;
104 } caa_c_transparent_union cds_wfs_stack_ptr_t
;
108 #include <urcu/static/wfstack.h>
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
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
123 * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
124 * cds_wfs_pop_all_blocking.
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
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
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
143 #else /* !_LGPL_SOURCE */
146 * cds_wfs_node_init: initialize wait-free stack node.
148 extern void cds_wfs_node_init(struct cds_wfs_node
*node
);
151 * cds_wfs_init: initialize wait-free stack (with lock). Pair with
154 extern void cds_wfs_init(struct cds_wfs_stack
*s
);
157 * cds_wfs_destroy: destroy wait-free stack (with lock). Pair with
160 extern void cds_wfs_destroy(struct cds_wfs_stack
*s
);
163 * __cds_wfs_init: initialize wait-free stack (no lock). Don't pair with
164 * any destroy function.
166 extern void __cds_wfs_init(struct __cds_wfs_stack
*s
);
169 * cds_wfs_empty: return whether wait-free stack is empty.
171 * No memory barrier is issued. No mutual exclusion is required.
173 extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack
);
176 * cds_wfs_push: push a node into the stack.
178 * Issues a full memory barrier before push. No mutual exclusion is
181 * Returns 0 if the stack was empty prior to adding the node.
182 * Returns non-zero otherwise.
184 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack
, struct cds_wfs_node
*node
);
187 * cds_wfs_pop_blocking: pop a node from the stack.
189 * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
191 extern struct cds_wfs_node
*cds_wfs_pop_blocking(struct cds_wfs_stack
*s
);
194 * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
196 * Same as cds_wfs_pop_blocking, but stores whether the stack was
197 * empty into state (CDS_WFS_STATE_LAST).
199 extern struct cds_wfs_node
*
200 cds_wfs_pop_with_state_blocking(struct cds_wfs_stack
*s
, int *state
);
203 * cds_wfs_pop_all_blocking: pop all nodes from a stack.
205 * Calls __cds_wfs_pop_all with an internal pop mutex held.
207 extern struct cds_wfs_head
*cds_wfs_pop_all_blocking(struct cds_wfs_stack
*s
);
210 * cds_wfs_first: get first node of a popped stack.
212 * Content written into the node before enqueue is guaranteed to be
213 * consistent, but no other memory ordering is ensured.
215 * Used by for-like iteration macros in urcu/wfstack.h:
216 * cds_wfs_for_each_blocking()
217 * cds_wfs_for_each_blocking_safe()
219 * Returns NULL if popped stack is empty, top stack node otherwise.
221 extern struct cds_wfs_node
*cds_wfs_first(struct cds_wfs_head
*head
);
224 * cds_wfs_next_blocking: get next node of a popped stack.
226 * Content written into the node before enqueue is guaranteed to be
227 * consistent, but no other memory ordering is ensured.
229 * Used by for-like iteration macros in urcu/wfstack.h:
230 * cds_wfs_for_each_blocking()
231 * cds_wfs_for_each_blocking_safe()
233 * Returns NULL if reached end of popped stack, non-NULL next stack
236 extern struct cds_wfs_node
*cds_wfs_next_blocking(struct cds_wfs_node
*node
);
239 * cds_wfs_next_nonblocking: get next node of a popped stack.
241 * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
244 extern struct cds_wfs_node
*cds_wfs_next_nonblocking(struct cds_wfs_node
*node
);
247 * cds_wfs_pop_lock: lock stack pop-protection mutex.
249 extern void cds_wfs_pop_lock(struct cds_wfs_stack
*s
);
252 * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
254 extern void cds_wfs_pop_unlock(struct cds_wfs_stack
*s
);
257 * __cds_wfs_pop_blocking: pop a node from the stack.
259 * Returns NULL if stack is empty.
261 * __cds_wfs_pop_blocking needs to be synchronized using one of the
262 * following techniques:
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).
272 extern struct cds_wfs_node
*__cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack
);
275 * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
277 * Same as __cds_wfs_pop_blocking, but stores whether the stack was
278 * empty into state (CDS_WFS_STATE_LAST).
280 extern struct cds_wfs_node
*
281 __cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack
,
285 * __cds_wfs_pop_nonblocking: pop a node from the stack.
287 * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
290 extern struct cds_wfs_node
*__cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack
);
293 * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
295 * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
296 * empty into state (CDS_WFS_STATE_LAST).
298 extern struct cds_wfs_node
*
299 __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack
,
303 * __cds_wfs_pop_all: pop all nodes from a stack.
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:
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).
319 extern struct cds_wfs_head
*__cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack
);
321 #endif /* !_LGPL_SOURCE */
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).
333 * Content written into each node before enqueue is guaranteed to be
334 * consistent, but no other memory ordering is ensured.
336 #define cds_wfs_for_each_blocking(head, node) \
337 for (node = cds_wfs_first(head); \
339 node = cds_wfs_next_blocking(node))
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
349 * Content written into each node before enqueue is guaranteed to be
350 * consistent, but no other memory ordering is ensured.
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); \
356 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
358 #endif /* _URCU_WFSTACK_H */