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 ((void *) -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
100 struct __cds_wfs_stack
*_s
;
101 struct cds_wfs_stack
*s
;
102 } __attribute__((__transparent_union__
)) cds_wfs_stack_ptr_t
;
106 #include <urcu/static/wfstack.h>
108 #define cds_wfs_node_init _cds_wfs_node_init
109 #define cds_wfs_init _cds_wfs_init
110 #define cds_wfs_destroy _cds_wfs_destroy
111 #define __cds_wfs_init ___cds_wfs_init
112 #define cds_wfs_empty _cds_wfs_empty
113 #define cds_wfs_push _cds_wfs_push
115 /* Locking performed internally */
116 #define cds_wfs_pop_blocking _cds_wfs_pop_blocking
117 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
118 #define cds_wfs_pop_all_blocking _cds_wfs_pop_all_blocking
121 * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
122 * cds_wfs_pop_all_blocking.
124 #define cds_wfs_first _cds_wfs_first
125 #define cds_wfs_next_blocking _cds_wfs_next_blocking
126 #define cds_wfs_next_nonblocking _cds_wfs_next_nonblocking
128 /* Pop locking with internal mutex */
129 #define cds_wfs_pop_lock _cds_wfs_pop_lock
130 #define cds_wfs_pop_unlock _cds_wfs_pop_unlock
132 /* Synchronization ensured by the caller. See synchronization table. */
133 #define __cds_wfs_pop_blocking ___cds_wfs_pop_blocking
134 #define __cds_wfs_pop_with_state_blocking \
135 ___cds_wfs_pop_with_state_blocking
136 #define __cds_wfs_pop_nonblocking ___cds_wfs_pop_nonblocking
137 #define __cds_wfs_pop_with_state_nonblocking \
138 ___cds_wfs_pop_with_state_nonblocking
139 #define __cds_wfs_pop_all ___cds_wfs_pop_all
141 #else /* !_LGPL_SOURCE */
144 * cds_wfs_node_init: initialize wait-free stack node.
146 extern void cds_wfs_node_init(struct cds_wfs_node
*node
);
149 * cds_wfs_init: initialize wait-free stack (with lock). Pair with
152 extern void cds_wfs_init(struct cds_wfs_stack
*s
);
155 * cds_wfs_destroy: destroy wait-free stack (with lock). Pair with
158 extern void cds_wfs_destroy(struct cds_wfs_stack
*s
);
161 * __cds_wfs_init: initialize wait-free stack (no lock). Don't pair with
162 * any destroy function.
164 extern void __cds_wfs_init(struct __cds_wfs_stack
*s
);
167 * cds_wfs_empty: return whether wait-free stack is empty.
169 * No memory barrier is issued. No mutual exclusion is required.
171 extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack
);
174 * cds_wfs_push: push a node into the stack.
176 * Issues a full memory barrier before push. No mutual exclusion is
179 * Returns 0 if the stack was empty prior to adding the node.
180 * Returns non-zero otherwise.
182 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack
, struct cds_wfs_node
*node
);
185 * cds_wfs_pop_blocking: pop a node from the stack.
187 * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
189 extern struct cds_wfs_node
*cds_wfs_pop_blocking(struct cds_wfs_stack
*s
);
192 * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
194 * Same as cds_wfs_pop_blocking, but stores whether the stack was
195 * empty into state (CDS_WFS_STATE_LAST).
197 extern struct cds_wfs_node
*
198 cds_wfs_pop_with_state_blocking(struct cds_wfs_stack
*s
, int *state
);
201 * cds_wfs_pop_all_blocking: pop all nodes from a stack.
203 * Calls __cds_wfs_pop_all with an internal pop mutex held.
205 extern struct cds_wfs_head
*cds_wfs_pop_all_blocking(struct cds_wfs_stack
*s
);
208 * cds_wfs_first: get first node of a popped stack.
210 * Content written into the node before enqueue is guaranteed to be
211 * consistent, but no other memory ordering is ensured.
213 * Used by for-like iteration macros in urcu/wfstack.h:
214 * cds_wfs_for_each_blocking()
215 * cds_wfs_for_each_blocking_safe()
217 * Returns NULL if popped stack is empty, top stack node otherwise.
219 extern struct cds_wfs_node
*cds_wfs_first(struct cds_wfs_head
*head
);
222 * cds_wfs_next_blocking: get next node of a popped stack.
224 * Content written into the node before enqueue is guaranteed to be
225 * consistent, but no other memory ordering is ensured.
227 * Used by for-like iteration macros in urcu/wfstack.h:
228 * cds_wfs_for_each_blocking()
229 * cds_wfs_for_each_blocking_safe()
231 * Returns NULL if reached end of popped stack, non-NULL next stack
234 extern struct cds_wfs_node
*cds_wfs_next_blocking(struct cds_wfs_node
*node
);
237 * cds_wfs_next_nonblocking: get next node of a popped stack.
239 * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
242 extern struct cds_wfs_node
*cds_wfs_next_nonblocking(struct cds_wfs_node
*node
);
245 * cds_wfs_pop_lock: lock stack pop-protection mutex.
247 extern void cds_wfs_pop_lock(struct cds_wfs_stack
*s
);
250 * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
252 extern void cds_wfs_pop_unlock(struct cds_wfs_stack
*s
);
255 * __cds_wfs_pop_blocking: pop a node from the stack.
257 * Returns NULL if stack is empty.
259 * __cds_wfs_pop_blocking needs to be synchronized using one of the
260 * following techniques:
262 * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
263 * section. The caller must wait for a grace period to pass before
264 * freeing the returned node or modifying the cds_wfs_node structure.
265 * 2) Using mutual exclusion (e.g. mutexes) to protect
266 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
267 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
268 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
270 extern struct cds_wfs_node
*__cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack
);
273 * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
275 * Same as __cds_wfs_pop_blocking, but stores whether the stack was
276 * empty into state (CDS_WFS_STATE_LAST).
278 extern struct cds_wfs_node
*
279 __cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack
,
283 * __cds_wfs_pop_nonblocking: pop a node from the stack.
285 * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
288 extern struct cds_wfs_node
*__cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack
);
291 * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
293 * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
294 * empty into state (CDS_WFS_STATE_LAST).
296 extern struct cds_wfs_node
*
297 __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack
,
301 * __cds_wfs_pop_all: pop all nodes from a stack.
303 * __cds_wfs_pop_all does not require any synchronization with other
304 * push, nor with other __cds_wfs_pop_all, but requires synchronization
305 * matching the technique used to synchronize __cds_wfs_pop_blocking:
307 * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
308 * section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
309 * must wait for a grace period to pass before freeing the returned
310 * node or modifying the cds_wfs_node structure. However, no RCU
311 * read-side critical section is needed around __cds_wfs_pop_all.
312 * 2) Using mutual exclusion (e.g. mutexes) to protect
313 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
314 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
315 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
317 extern struct cds_wfs_head
*__cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack
);
319 #endif /* !_LGPL_SOURCE */
326 * cds_wfs_for_each_blocking: Iterate over all nodes returned by
327 * __cds_wfs_pop_all().
328 * @head: head of the queue (struct cds_wfs_head pointer).
329 * @node: iterator (struct cds_wfs_node pointer).
331 * Content written into each node before enqueue is guaranteed to be
332 * consistent, but no other memory ordering is ensured.
334 #define cds_wfs_for_each_blocking(head, node) \
335 for (node = cds_wfs_first(head); \
337 node = cds_wfs_next_blocking(node))
340 * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
341 * __cds_wfs_pop_all(). Safe against deletion.
342 * @head: head of the queue (struct cds_wfs_head pointer).
343 * @node: iterator (struct cds_wfs_node pointer).
344 * @n: struct cds_wfs_node pointer holding the next pointer (used
347 * Content written into each node before enqueue is guaranteed to be
348 * consistent, but no other memory ordering is ensured.
350 #define cds_wfs_for_each_blocking_safe(head, node, n) \
351 for (node = cds_wfs_first(head), \
352 n = (node ? cds_wfs_next_blocking(node) : NULL); \
354 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
356 #endif /* _URCU_WFSTACK_H */