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
;
90 struct cds_wfs_stack
{
91 struct cds_wfs_head
*head
;
96 * The transparent union allows calling functions that work on both
97 * struct cds_wfs_stack and struct __cds_wfs_stack on any of those two
100 typedef union __attribute__((__transparent_union__
)) {
101 struct __cds_wfs_stack
*_s
;
102 struct cds_wfs_stack
*s
;
103 } cds_wfs_stack_ptr_t
;
107 #include <urcu/static/wfstack.h>
109 #define cds_wfs_node_init _cds_wfs_node_init
110 #define cds_wfs_init _cds_wfs_init
111 #define cds_wfs_empty _cds_wfs_empty
112 #define cds_wfs_push _cds_wfs_push
114 /* Locking performed internally */
115 #define cds_wfs_pop_blocking _cds_wfs_pop_blocking
116 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
117 #define cds_wfs_pop_all_blocking _cds_wfs_pop_all_blocking
120 * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
121 * cds_wfs_pop_all_blocking.
123 #define cds_wfs_first _cds_wfs_first
124 #define cds_wfs_next_blocking _cds_wfs_next_blocking
125 #define cds_wfs_next_nonblocking _cds_wfs_next_nonblocking
127 /* Pop locking with internal mutex */
128 #define cds_wfs_pop_lock _cds_wfs_pop_lock
129 #define cds_wfs_pop_unlock _cds_wfs_pop_unlock
131 /* Synchronization ensured by the caller. See synchronization table. */
132 #define __cds_wfs_pop_blocking ___cds_wfs_pop_blocking
133 #define __cds_wfs_pop_with_state_blocking \
134 ___cds_wfs_pop_with_state_blocking
135 #define __cds_wfs_pop_nonblocking ___cds_wfs_pop_nonblocking
136 #define __cds_wfs_pop_with_state_nonblocking \
137 ___cds_wfs_pop_with_state_nonblocking
138 #define __cds_wfs_pop_all ___cds_wfs_pop_all
140 #else /* !_LGPL_SOURCE */
143 * cds_wfs_node_init: initialize wait-free stack node.
145 extern void cds_wfs_node_init(struct cds_wfs_node
*node
);
148 * cds_wfs_init: initialize wait-free stack.
150 extern void cds_wfs_init(struct cds_wfs_stack
*s
);
153 * __cds_wfs_init: initialize wait-free stack.
155 extern void __cds_wfs_init(struct __cds_wfs_stack
*s
);
158 * cds_wfs_empty: return whether wait-free stack is empty.
160 * No memory barrier is issued. No mutual exclusion is required.
162 extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack
);
165 * cds_wfs_push: push a node into the stack.
167 * Issues a full memory barrier before push. No mutual exclusion is
170 * Returns 0 if the stack was empty prior to adding the node.
171 * Returns non-zero otherwise.
173 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack
, struct cds_wfs_node
*node
);
176 * cds_wfs_pop_blocking: pop a node from the stack.
178 * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
180 extern struct cds_wfs_node
*cds_wfs_pop_blocking(struct cds_wfs_stack
*s
);
183 * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
185 * Same as cds_wfs_pop_blocking, but stores whether the stack was
186 * empty into state (CDS_WFS_STATE_LAST).
188 extern struct cds_wfs_node
*
189 cds_wfs_pop_with_state_blocking(struct cds_wfs_stack
*s
, int *state
);
192 * cds_wfs_pop_all_blocking: pop all nodes from a stack.
194 * Calls __cds_wfs_pop_all with an internal pop mutex held.
196 extern struct cds_wfs_head
*cds_wfs_pop_all_blocking(struct cds_wfs_stack
*s
);
199 * cds_wfs_first: get first node of a popped stack.
201 * Content written into the node before enqueue is guaranteed to be
202 * consistent, but no other memory ordering is ensured.
204 * Used by for-like iteration macros in urcu/wfstack.h:
205 * cds_wfs_for_each_blocking()
206 * cds_wfs_for_each_blocking_safe()
208 * Returns NULL if popped stack is empty, top stack node otherwise.
210 extern struct cds_wfs_node
*cds_wfs_first(struct cds_wfs_head
*head
);
213 * cds_wfs_next_blocking: get next node of a popped stack.
215 * Content written into the node before enqueue is guaranteed to be
216 * consistent, but no other memory ordering is ensured.
218 * Used by for-like iteration macros in urcu/wfstack.h:
219 * cds_wfs_for_each_blocking()
220 * cds_wfs_for_each_blocking_safe()
222 * Returns NULL if reached end of popped stack, non-NULL next stack
225 extern struct cds_wfs_node
*cds_wfs_next_blocking(struct cds_wfs_node
*node
);
228 * cds_wfs_next_nonblocking: get next node of a popped stack.
230 * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
233 extern struct cds_wfs_node
*cds_wfs_next_nonblocking(struct cds_wfs_node
*node
);
236 * cds_wfs_pop_lock: lock stack pop-protection mutex.
238 extern void cds_wfs_pop_lock(struct cds_wfs_stack
*s
);
241 * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
243 extern void cds_wfs_pop_unlock(struct cds_wfs_stack
*s
);
246 * __cds_wfs_pop_blocking: pop a node from the stack.
248 * Returns NULL if stack is empty.
250 * __cds_wfs_pop_blocking needs to be synchronized using one of the
251 * following techniques:
253 * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
254 * section. The caller must wait for a grace period to pass before
255 * freeing the returned node or modifying the cds_wfs_node structure.
256 * 2) Using mutual exclusion (e.g. mutexes) to protect
257 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
258 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
259 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
261 extern struct cds_wfs_node
*__cds_wfs_pop_blocking(struct cds_wfs_stack
*s
);
264 * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
266 * Same as __cds_wfs_pop_blocking, but stores whether the stack was
267 * empty into state (CDS_WFS_STATE_LAST).
269 extern struct cds_wfs_node
*
270 __cds_wfs_pop_with_state_blocking(struct cds_wfs_stack
*s
, int *state
);
273 * __cds_wfs_pop_nonblocking: pop a node from the stack.
275 * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
278 extern struct cds_wfs_node
*__cds_wfs_pop_nonblocking(struct cds_wfs_stack
*s
);
281 * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
283 * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
284 * empty into state (CDS_WFS_STATE_LAST).
286 extern struct cds_wfs_node
*
287 __cds_wfs_pop_with_state_nonblocking(struct cds_wfs_stack
*s
,
291 * __cds_wfs_pop_all: pop all nodes from a stack.
293 * __cds_wfs_pop_all does not require any synchronization with other
294 * push, nor with other __cds_wfs_pop_all, but requires synchronization
295 * matching the technique used to synchronize __cds_wfs_pop_blocking:
297 * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
298 * section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
299 * must wait for a grace period to pass before freeing the returned
300 * node or modifying the cds_wfs_node structure. However, no RCU
301 * read-side critical section is needed around __cds_wfs_pop_all.
302 * 2) Using mutual exclusion (e.g. mutexes) to protect
303 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
304 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
305 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
307 extern struct cds_wfs_head
*__cds_wfs_pop_all(struct cds_wfs_stack
*s
);
309 #endif /* !_LGPL_SOURCE */
316 * cds_wfs_for_each_blocking: Iterate over all nodes returned by
317 * __cds_wfs_pop_all().
318 * @head: head of the queue (struct cds_wfs_head pointer).
319 * @node: iterator (struct cds_wfs_node pointer).
321 * Content written into each node before enqueue is guaranteed to be
322 * consistent, but no other memory ordering is ensured.
324 #define cds_wfs_for_each_blocking(head, node) \
325 for (node = cds_wfs_first(head); \
327 node = cds_wfs_next_blocking(node))
330 * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
331 * __cds_wfs_pop_all(). Safe against deletion.
332 * @head: head of the queue (struct cds_wfs_head pointer).
333 * @node: iterator (struct cds_wfs_node pointer).
334 * @n: struct cds_wfs_node pointer holding the next pointer (used
337 * Content written into each node before enqueue is guaranteed to be
338 * consistent, but no other memory ordering is ensured.
340 #define cds_wfs_for_each_blocking_safe(head, node, n) \
341 for (node = cds_wfs_first(head), \
342 n = (node ? cds_wfs_next_blocking(node) : NULL); \
344 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
346 #endif /* _URCU_WFSTACK_H */