| 1 | #ifndef _URCU_WFSTACK_H |
| 2 | #define _URCU_WFSTACK_H |
| 3 | |
| 4 | /* |
| 5 | * urcu/wfstack.h |
| 6 | * |
| 7 | * Userspace RCU library - Stack with wait-free push, blocking traversal. |
| 8 | * |
| 9 | * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 10 | * |
| 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. |
| 15 | * |
| 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. |
| 20 | * |
| 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 |
| 24 | */ |
| 25 | |
| 26 | #include <pthread.h> |
| 27 | #include <assert.h> |
| 28 | #include <stdbool.h> |
| 29 | #include <urcu/compiler.h> |
| 30 | |
| 31 | #ifdef __cplusplus |
| 32 | extern "C" { |
| 33 | #endif |
| 34 | |
| 35 | /* |
| 36 | * Stack with wait-free push, blocking traversal. |
| 37 | * |
| 38 | * Stack implementing push, pop, pop_all operations, as well as iterator |
| 39 | * on the stack head returned by pop_all. |
| 40 | * |
| 41 | * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty, |
| 42 | * cds_wfs_first. |
| 43 | * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next, |
| 44 | * iteration on stack head returned by pop_all. |
| 45 | * |
| 46 | * Synchronization table: |
| 47 | * |
| 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 "-". |
| 51 | * |
| 52 | * cds_wfs_push __cds_wfs_pop __cds_wfs_pop_all |
| 53 | * cds_wfs_push - - - |
| 54 | * __cds_wfs_pop - X X |
| 55 | * __cds_wfs_pop_all - X - |
| 56 | * |
| 57 | * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide |
| 58 | * synchronization. |
| 59 | */ |
| 60 | |
| 61 | #define CDS_WFS_WOULDBLOCK ((void *) -1UL) |
| 62 | |
| 63 | enum cds_wfs_state { |
| 64 | CDS_WFS_STATE_LAST = (1U << 0), |
| 65 | }; |
| 66 | |
| 67 | /* |
| 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. |
| 71 | */ |
| 72 | struct cds_wfs_node { |
| 73 | struct cds_wfs_node *next; |
| 74 | }; |
| 75 | |
| 76 | /* |
| 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 |
| 80 | * types. |
| 81 | */ |
| 82 | struct cds_wfs_head { |
| 83 | struct cds_wfs_node node; |
| 84 | }; |
| 85 | |
| 86 | struct cds_wfs_stack { |
| 87 | struct cds_wfs_head *head; |
| 88 | pthread_mutex_t lock; |
| 89 | }; |
| 90 | |
| 91 | #ifdef _LGPL_SOURCE |
| 92 | |
| 93 | #include <urcu/static/wfstack.h> |
| 94 | |
| 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 |
| 99 | |
| 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 |
| 104 | |
| 105 | /* |
| 106 | * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or |
| 107 | * cds_wfs_pop_all_blocking. |
| 108 | */ |
| 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 |
| 112 | |
| 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 |
| 116 | |
| 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 |
| 125 | |
| 126 | #else /* !_LGPL_SOURCE */ |
| 127 | |
| 128 | /* |
| 129 | * cds_wfs_node_init: initialize wait-free stack node. |
| 130 | */ |
| 131 | extern void cds_wfs_node_init(struct cds_wfs_node *node); |
| 132 | |
| 133 | /* |
| 134 | * cds_wfs_init: initialize wait-free stack. |
| 135 | */ |
| 136 | extern void cds_wfs_init(struct cds_wfs_stack *s); |
| 137 | |
| 138 | /* |
| 139 | * cds_wfs_empty: return whether wait-free stack is empty. |
| 140 | * |
| 141 | * No memory barrier is issued. No mutual exclusion is required. |
| 142 | */ |
| 143 | extern bool cds_wfs_empty(struct cds_wfs_stack *s); |
| 144 | |
| 145 | /* |
| 146 | * cds_wfs_push: push a node into the stack. |
| 147 | * |
| 148 | * Issues a full memory barrier before push. No mutual exclusion is |
| 149 | * required. |
| 150 | * |
| 151 | * Returns 0 if the stack was empty prior to adding the node. |
| 152 | * Returns non-zero otherwise. |
| 153 | */ |
| 154 | extern int cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node); |
| 155 | |
| 156 | /* |
| 157 | * cds_wfs_pop_blocking: pop a node from the stack. |
| 158 | * |
| 159 | * Calls __cds_wfs_pop_blocking with an internal pop mutex held. |
| 160 | */ |
| 161 | extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s); |
| 162 | |
| 163 | /* |
| 164 | * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state. |
| 165 | * |
| 166 | * Same as cds_wfs_pop_blocking, but stores whether the stack was |
| 167 | * empty into state (CDS_WFS_STATE_LAST). |
| 168 | */ |
| 169 | extern struct cds_wfs_node * |
| 170 | cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state); |
| 171 | |
| 172 | /* |
| 173 | * cds_wfs_pop_all_blocking: pop all nodes from a stack. |
| 174 | * |
| 175 | * Calls __cds_wfs_pop_all with an internal pop mutex held. |
| 176 | */ |
| 177 | extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s); |
| 178 | |
| 179 | /* |
| 180 | * cds_wfs_first: get first node of a popped stack. |
| 181 | * |
| 182 | * Content written into the node before enqueue is guaranteed to be |
| 183 | * consistent, but no other memory ordering is ensured. |
| 184 | * |
| 185 | * Used by for-like iteration macros in urcu/wfstack.h: |
| 186 | * cds_wfs_for_each_blocking() |
| 187 | * cds_wfs_for_each_blocking_safe() |
| 188 | * |
| 189 | * Returns NULL if popped stack is empty, top stack node otherwise. |
| 190 | */ |
| 191 | extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head); |
| 192 | |
| 193 | /* |
| 194 | * cds_wfs_next_blocking: get next node of a popped stack. |
| 195 | * |
| 196 | * Content written into the node before enqueue is guaranteed to be |
| 197 | * consistent, but no other memory ordering is ensured. |
| 198 | * |
| 199 | * Used by for-like iteration macros in urcu/wfstack.h: |
| 200 | * cds_wfs_for_each_blocking() |
| 201 | * cds_wfs_for_each_blocking_safe() |
| 202 | * |
| 203 | * Returns NULL if reached end of popped stack, non-NULL next stack |
| 204 | * node otherwise. |
| 205 | */ |
| 206 | extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node); |
| 207 | |
| 208 | /* |
| 209 | * cds_wfs_next_nonblocking: get next node of a popped stack. |
| 210 | * |
| 211 | * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it |
| 212 | * needs to block. |
| 213 | */ |
| 214 | extern struct cds_wfs_node *cds_wfs_next_nonblocking(struct cds_wfs_node *node); |
| 215 | |
| 216 | /* |
| 217 | * cds_wfs_pop_lock: lock stack pop-protection mutex. |
| 218 | */ |
| 219 | extern void cds_wfs_pop_lock(struct cds_wfs_stack *s); |
| 220 | |
| 221 | /* |
| 222 | * cds_wfs_pop_unlock: unlock stack pop-protection mutex. |
| 223 | */ |
| 224 | extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s); |
| 225 | |
| 226 | /* |
| 227 | * __cds_wfs_pop_blocking: pop a node from the stack. |
| 228 | * |
| 229 | * Returns NULL if stack is empty. |
| 230 | * |
| 231 | * __cds_wfs_pop_blocking needs to be synchronized using one of the |
| 232 | * following techniques: |
| 233 | * |
| 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). |
| 241 | */ |
| 242 | extern struct cds_wfs_node *__cds_wfs_pop_blocking(struct cds_wfs_stack *s); |
| 243 | |
| 244 | /* |
| 245 | * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state. |
| 246 | * |
| 247 | * Same as __cds_wfs_pop_blocking, but stores whether the stack was |
| 248 | * empty into state (CDS_WFS_STATE_LAST). |
| 249 | */ |
| 250 | extern struct cds_wfs_node * |
| 251 | __cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state); |
| 252 | |
| 253 | /* |
| 254 | * __cds_wfs_pop_nonblocking: pop a node from the stack. |
| 255 | * |
| 256 | * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if |
| 257 | * it needs to block. |
| 258 | */ |
| 259 | extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(struct cds_wfs_stack *s); |
| 260 | |
| 261 | /* |
| 262 | * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state. |
| 263 | * |
| 264 | * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was |
| 265 | * empty into state (CDS_WFS_STATE_LAST). |
| 266 | */ |
| 267 | extern struct cds_wfs_node * |
| 268 | __cds_wfs_pop_with_state_nonblocking(struct cds_wfs_stack *s, |
| 269 | int *state); |
| 270 | |
| 271 | /* |
| 272 | * __cds_wfs_pop_all: pop all nodes from a stack. |
| 273 | * |
| 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: |
| 277 | * |
| 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). |
| 287 | */ |
| 288 | extern struct cds_wfs_head *__cds_wfs_pop_all(struct cds_wfs_stack *s); |
| 289 | |
| 290 | #endif /* !_LGPL_SOURCE */ |
| 291 | |
| 292 | #ifdef __cplusplus |
| 293 | } |
| 294 | #endif |
| 295 | |
| 296 | /* |
| 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). |
| 301 | * |
| 302 | * Content written into each node before enqueue is guaranteed to be |
| 303 | * consistent, but no other memory ordering is ensured. |
| 304 | */ |
| 305 | #define cds_wfs_for_each_blocking(head, node) \ |
| 306 | for (node = cds_wfs_first(head); \ |
| 307 | node != NULL; \ |
| 308 | node = cds_wfs_next_blocking(node)) |
| 309 | |
| 310 | /* |
| 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 |
| 316 | * internally). |
| 317 | * |
| 318 | * Content written into each node before enqueue is guaranteed to be |
| 319 | * consistent, but no other memory ordering is ensured. |
| 320 | */ |
| 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); \ |
| 324 | node != NULL; \ |
| 325 | node = n, n = (node ? cds_wfs_next_blocking(node) : NULL)) |
| 326 | |
| 327 | #endif /* _URCU_WFSTACK_H */ |