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 * In C, 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 * In C++, implement static inline wrappers using function overloading
100 * to obtain an API similar to C.
102 * Avoid complaints from clang++ not knowing the transparent union
105 #if defined(__clang__)
106 #pragma clang diagnostic push
107 #pragma clang diagnostic ignored "-Wignored-attributes"
110 struct __cds_wfs_stack
*_s
;
111 struct cds_wfs_stack
*s
;
112 } __attribute__((__transparent_union__
)) cds_wfs_stack_ptr_t
;
113 #if defined(__clang__)
114 #pragma clang diagnostic pop
119 #include <urcu/static/wfstack.h>
121 #define cds_wfs_node_init _cds_wfs_node_init
122 #define cds_wfs_init _cds_wfs_init
123 #define cds_wfs_destroy _cds_wfs_destroy
124 #define __cds_wfs_init ___cds_wfs_init
125 #define cds_wfs_empty _cds_wfs_empty
126 #define cds_wfs_push _cds_wfs_push
128 /* Locking performed internally */
129 #define cds_wfs_pop_blocking _cds_wfs_pop_blocking
130 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
131 #define cds_wfs_pop_all_blocking _cds_wfs_pop_all_blocking
134 * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
135 * cds_wfs_pop_all_blocking.
137 #define cds_wfs_first _cds_wfs_first
138 #define cds_wfs_next_blocking _cds_wfs_next_blocking
139 #define cds_wfs_next_nonblocking _cds_wfs_next_nonblocking
141 /* Pop locking with internal mutex */
142 #define cds_wfs_pop_lock _cds_wfs_pop_lock
143 #define cds_wfs_pop_unlock _cds_wfs_pop_unlock
145 /* Synchronization ensured by the caller. See synchronization table. */
146 #define __cds_wfs_pop_blocking ___cds_wfs_pop_blocking
147 #define __cds_wfs_pop_with_state_blocking \
148 ___cds_wfs_pop_with_state_blocking
149 #define __cds_wfs_pop_nonblocking ___cds_wfs_pop_nonblocking
150 #define __cds_wfs_pop_with_state_nonblocking \
151 ___cds_wfs_pop_with_state_nonblocking
152 #define __cds_wfs_pop_all ___cds_wfs_pop_all
154 #else /* !_LGPL_SOURCE */
157 * cds_wfs_node_init: initialize wait-free stack node.
159 extern void cds_wfs_node_init(struct cds_wfs_node
*node
);
162 * cds_wfs_init: initialize wait-free stack (with lock). Pair with
165 extern void cds_wfs_init(struct cds_wfs_stack
*s
);
168 * cds_wfs_destroy: destroy wait-free stack (with lock). Pair with
171 extern void cds_wfs_destroy(struct cds_wfs_stack
*s
);
174 * __cds_wfs_init: initialize wait-free stack (no lock). Don't pair with
175 * any destroy function.
177 extern void __cds_wfs_init(struct __cds_wfs_stack
*s
);
180 * cds_wfs_empty: return whether wait-free stack is empty.
182 * No memory barrier is issued. No mutual exclusion is required.
184 extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack
);
187 * cds_wfs_push: push a node into the stack.
189 * Issues a full memory barrier before push. No mutual exclusion is
192 * Returns 0 if the stack was empty prior to adding the node.
193 * Returns non-zero otherwise.
195 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack
, struct cds_wfs_node
*node
);
198 * cds_wfs_pop_blocking: pop a node from the stack.
200 * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
202 extern struct cds_wfs_node
*cds_wfs_pop_blocking(struct cds_wfs_stack
*s
);
205 * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
207 * Same as cds_wfs_pop_blocking, but stores whether the stack was
208 * empty into state (CDS_WFS_STATE_LAST).
210 extern struct cds_wfs_node
*
211 cds_wfs_pop_with_state_blocking(struct cds_wfs_stack
*s
, int *state
);
214 * cds_wfs_pop_all_blocking: pop all nodes from a stack.
216 * Calls __cds_wfs_pop_all with an internal pop mutex held.
218 extern struct cds_wfs_head
*cds_wfs_pop_all_blocking(struct cds_wfs_stack
*s
);
221 * cds_wfs_first: get first node of a popped stack.
223 * Content written into the node before enqueue is guaranteed to be
224 * consistent, but no other memory ordering is ensured.
226 * Used by for-like iteration macros in urcu/wfstack.h:
227 * cds_wfs_for_each_blocking()
228 * cds_wfs_for_each_blocking_safe()
230 * Returns NULL if popped stack is empty, top stack node otherwise.
232 extern struct cds_wfs_node
*cds_wfs_first(struct cds_wfs_head
*head
);
235 * cds_wfs_next_blocking: get next node of a popped stack.
237 * Content written into the node before enqueue is guaranteed to be
238 * consistent, but no other memory ordering is ensured.
240 * Used by for-like iteration macros in urcu/wfstack.h:
241 * cds_wfs_for_each_blocking()
242 * cds_wfs_for_each_blocking_safe()
244 * Returns NULL if reached end of popped stack, non-NULL next stack
247 extern struct cds_wfs_node
*cds_wfs_next_blocking(struct cds_wfs_node
*node
);
250 * cds_wfs_next_nonblocking: get next node of a popped stack.
252 * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
255 extern struct cds_wfs_node
*cds_wfs_next_nonblocking(struct cds_wfs_node
*node
);
258 * cds_wfs_pop_lock: lock stack pop-protection mutex.
260 extern void cds_wfs_pop_lock(struct cds_wfs_stack
*s
);
263 * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
265 extern void cds_wfs_pop_unlock(struct cds_wfs_stack
*s
);
268 * __cds_wfs_pop_blocking: pop a node from the stack.
270 * Returns NULL if stack is empty.
272 * __cds_wfs_pop_blocking needs to be synchronized using one of the
273 * following techniques:
275 * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
276 * section. The caller must wait for a grace period to pass before
277 * freeing the returned node or modifying the cds_wfs_node structure.
278 * 2) Using mutual exclusion (e.g. mutexes) to protect
279 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
280 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
281 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
283 extern struct cds_wfs_node
*__cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack
);
286 * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
288 * Same as __cds_wfs_pop_blocking, but stores whether the stack was
289 * empty into state (CDS_WFS_STATE_LAST).
291 extern struct cds_wfs_node
*
292 __cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack
,
296 * __cds_wfs_pop_nonblocking: pop a node from the stack.
298 * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
301 extern struct cds_wfs_node
*__cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack
);
304 * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
306 * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
307 * empty into state (CDS_WFS_STATE_LAST).
309 extern struct cds_wfs_node
*
310 __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack
,
314 * __cds_wfs_pop_all: pop all nodes from a stack.
316 * __cds_wfs_pop_all does not require any synchronization with other
317 * push, nor with other __cds_wfs_pop_all, but requires synchronization
318 * matching the technique used to synchronize __cds_wfs_pop_blocking:
320 * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
321 * section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
322 * must wait for a grace period to pass before freeing the returned
323 * node or modifying the cds_wfs_node structure. However, no RCU
324 * read-side critical section is needed around __cds_wfs_pop_all.
325 * 2) Using mutual exclusion (e.g. mutexes) to protect
326 * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
327 * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
328 * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
330 extern struct cds_wfs_head
*__cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack
);
332 #endif /* !_LGPL_SOURCE */
335 * cds_wfs_for_each_blocking: Iterate over all nodes returned by
336 * __cds_wfs_pop_all().
337 * @head: head of the queue (struct cds_wfs_head pointer).
338 * @node: iterator (struct cds_wfs_node pointer).
340 * Content written into each node before enqueue is guaranteed to be
341 * consistent, but no other memory ordering is ensured.
343 #define cds_wfs_for_each_blocking(head, node) \
344 for (node = cds_wfs_first(head); \
346 node = cds_wfs_next_blocking(node))
349 * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
350 * __cds_wfs_pop_all(). Safe against deletion.
351 * @head: head of the queue (struct cds_wfs_head pointer).
352 * @node: iterator (struct cds_wfs_node pointer).
353 * @n: struct cds_wfs_node pointer holding the next pointer (used
356 * Content written into each node before enqueue is guaranteed to be
357 * consistent, but no other memory ordering is ensured.
359 #define cds_wfs_for_each_blocking_safe(head, node, n) \
360 for (node = cds_wfs_first(head), \
361 n = (node ? cds_wfs_next_blocking(node) : NULL); \
363 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
369 * In C++, implement static inline wrappers using function overloading
370 * to obtain an API similar to C.
373 static inline cds_wfs_stack_ptr_t
cds_wfs_stack_cast(struct __cds_wfs_stack
*s
)
375 cds_wfs_stack_ptr_t ret
= {
381 static inline cds_wfs_stack_ptr_t
cds_wfs_stack_cast(struct cds_wfs_stack
*s
)
383 cds_wfs_stack_ptr_t ret
= {
389 template<typename T
> static inline bool cds_wfs_empty(T s
)
391 return cds_wfs_empty(cds_wfs_stack_cast(s
));
394 template<typename T
> static inline int cds_wfs_push(T s
, struct cds_wfs_node
*node
)
396 return cds_wfs_push(cds_wfs_stack_cast(s
), node
);
399 template<typename T
> static inline struct cds_wfs_node
*__cds_wfs_pop_blocking(T s
)
401 return __cds_wfs_pop_blocking(cds_wfs_stack_cast(s
));
404 template<typename T
> static inline struct cds_wfs_node
*
405 __cds_wfs_pop_with_state_blocking(T s
, int *state
)
407 return __cds_wfs_pop_with_state_blocking(cds_wfs_stack_cast(s
), state
);
410 template<typename T
> static inline struct cds_wfs_node
*__cds_wfs_pop_nonblocking(T s
)
413 return __cds_wfs_pop_nonblocking(cds_wfs_stack_cast(s
));
416 template<typename T
> static inline struct cds_wfs_node
*
417 __cds_wfs_pop_with_state_nonblocking(T s
, int *state
)
419 return __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_cast(s
), state
);
422 template<typename T
> static inline struct cds_wfs_head
*__cds_wfs_pop_all(T s
)
424 return __cds_wfs_pop_all(cds_wfs_stack_cast(s
));
429 #endif /* _URCU_WFSTACK_H */