include/urcu/wfstack.h

   1 // SPDX-FileCopyrightText: 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   2 //
   3 // SPDX-License-Identifier: LGPL-2.1-or-later
   4
   5 #ifndef _URCU_WFSTACK_H
   6 #define _URCU_WFSTACK_H
   7
   8 /*
   9  * Userspace RCU library - Stack with wait-free push, blocking traversal.
  10  */
  11
  12 #include <pthread.h>
  13 #include <stdbool.h>
  14 #include <urcu/compiler.h>
  15
  16 #ifdef __cplusplus
  17 extern "C" {
  18 #endif
  19
  20 /*
  21  * Stack with wait-free push, blocking traversal.
  22  *
  23  * Stack implementing push, pop, pop_all operations, as well as iterator
  24  * on the stack head returned by pop_all.
  25  *
  26  * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
  27  *                       cds_wfs_first.
  28  * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
  29  *                      iteration on stack head returned by pop_all.
  30  *
  31  * Synchronization table:
  32  *
  33  * External synchronization techniques described in the API below is
  34  * required between pairs marked with "X". No external synchronization
  35  * required between pairs marked with "-".
  36  *
  37  *                      cds_wfs_push  __cds_wfs_pop  __cds_wfs_pop_all
  38  * cds_wfs_push               -              -                  -
  39  * __cds_wfs_pop              -              X                  X
  40  * __cds_wfs_pop_all          -              X                  -
  41  *
  42  * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
  43  * synchronization.
  44  */
  45
  46 #define CDS_WFS_WOULDBLOCK      ((struct cds_wfs_node *) -1UL)
  47
  48 enum cds_wfs_state {
  49         CDS_WFS_STATE_LAST =            (1U << 0),
  50 };
  51
  52 /*
  53  * struct cds_wfs_node is returned by __cds_wfs_pop, and also used as
  54  * iterator on stack. It is not safe to dereference the node next
  55  * pointer when returned by __cds_wfs_pop_blocking.
  56  */
  57 struct cds_wfs_node {
  58         struct cds_wfs_node *next;
  59 };
  60
  61 /*
  62  * struct cds_wfs_head is returned by __cds_wfs_pop_all, and can be used
  63  * to begin iteration on the stack. "node" needs to be the first field of
  64  * cds_wfs_head, so the end-of-stack pointer value can be used for both
  65  * types.
  66  */
  67 struct cds_wfs_head {
  68         struct cds_wfs_node node;
  69 };
  70
  71 struct __cds_wfs_stack {
  72         struct cds_wfs_head *head;
  73 };
  74
  75 struct cds_wfs_stack {
  76         struct cds_wfs_head *head;
  77         pthread_mutex_t lock;
  78 };
  79
  80 /*
  81  * In C, the transparent union allows calling functions that work on both
  82  * struct cds_wfs_stack and struct __cds_wfs_stack on any of those two
  83  * types.
  84  *
  85  * In C++, implement static inline wrappers using function overloading
  86  * to obtain an API similar to C.
  87  *
  88  * Avoid complaints from clang++ not knowing the transparent union
  89  * attribute.
  90  */
  91 #if defined(__clang__)
  92 #pragma clang diagnostic push
  93 #pragma clang diagnostic ignored "-Wignored-attributes"
  94 #endif
  95 typedef union {
  96         struct __cds_wfs_stack *_s;
  97         struct cds_wfs_stack *s;
  98 } __attribute__((__transparent_union__)) cds_wfs_stack_ptr_t;
  99
 100 typedef union {
 101         const struct __cds_wfs_stack *_s;
 102         const struct cds_wfs_stack *s;
 103 } __attribute__((__transparent_union__)) cds_wfs_stack_const_ptr_t;
 104 #if defined(__clang__)
 105 #pragma clang diagnostic pop
 106 #endif
 107
 108 #ifdef _LGPL_SOURCE
 109
 110 #include <urcu/static/wfstack.h>
 111
 112 #define cds_wfs_node_init               _cds_wfs_node_init
 113 #define cds_wfs_init                    _cds_wfs_init
 114 #define cds_wfs_destroy                 _cds_wfs_destroy
 115 #define __cds_wfs_init                  ___cds_wfs_init
 116 #define cds_wfs_empty                   _cds_wfs_empty
 117 #define cds_wfs_push                    _cds_wfs_push
 118
 119 /* Locking performed internally */
 120 #define cds_wfs_pop_blocking            _cds_wfs_pop_blocking
 121 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
 122 #define cds_wfs_pop_all_blocking        _cds_wfs_pop_all_blocking
 123
 124 /*
 125  * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
 126  * cds_wfs_pop_all_blocking.
 127  */
 128 #define cds_wfs_first                   _cds_wfs_first
 129 #define cds_wfs_next_blocking           _cds_wfs_next_blocking
 130 #define cds_wfs_next_nonblocking        _cds_wfs_next_nonblocking
 131
 132 /* Pop locking with internal mutex */
 133 #define cds_wfs_pop_lock                _cds_wfs_pop_lock
 134 #define cds_wfs_pop_unlock              _cds_wfs_pop_unlock
 135
 136 /* Synchronization ensured by the caller. See synchronization table. */
 137 #define __cds_wfs_pop_blocking          ___cds_wfs_pop_blocking
 138 #define __cds_wfs_pop_with_state_blocking       \
 139                                         ___cds_wfs_pop_with_state_blocking
 140 #define __cds_wfs_pop_nonblocking       ___cds_wfs_pop_nonblocking
 141 #define __cds_wfs_pop_with_state_nonblocking    \
 142                                         ___cds_wfs_pop_with_state_nonblocking
 143 #define __cds_wfs_pop_all               ___cds_wfs_pop_all
 144
 145 #else /* !_LGPL_SOURCE */
 146
 147 /*
 148  * cds_wfs_node_init: initialize wait-free stack node.
 149  */
 150 extern void cds_wfs_node_init(struct cds_wfs_node *node);
 151
 152 /*
 153  * cds_wfs_init: initialize wait-free stack (with lock). Pair with
 154  * cds_wfs_destroy().
 155  */
 156 extern void cds_wfs_init(struct cds_wfs_stack *s);
 157
 158 /*
 159  * cds_wfs_destroy: destroy wait-free stack (with lock). Pair with
 160  * cds_wfs_init().
 161  */
 162 extern void cds_wfs_destroy(struct cds_wfs_stack *s);
 163
 164 /*
 165  * __cds_wfs_init: initialize wait-free stack (no lock). Don't pair with
 166  * any destroy function.
 167  */
 168 extern void __cds_wfs_init(struct __cds_wfs_stack *s);
 169
 170 /*
 171  * cds_wfs_empty: return whether wait-free stack is empty.
 172  *
 173  * No memory barrier is issued. No mutual exclusion is required.
 174  */
 175 extern bool cds_wfs_empty(cds_wfs_stack_const_ptr_t u_stack);
 176
 177 /*
 178  * cds_wfs_push: push a node into the stack.
 179  *
 180  * Issues a full memory barrier before push. No mutual exclusion is
 181  * required.
 182  *
 183  * Returns 0 if the stack was empty prior to adding the node.
 184  * Returns non-zero otherwise.
 185  */
 186 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node);
 187
 188 /*
 189  * cds_wfs_pop_blocking: pop a node from the stack.
 190  *
 191  * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
 192  */
 193 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 194
 195 /*
 196  * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 197  *
 198  * Same as cds_wfs_pop_blocking, but stores whether the stack was
 199  * empty into state (CDS_WFS_STATE_LAST).
 200  */
 201 extern struct cds_wfs_node *
 202         cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
 203
 204 /*
 205  * cds_wfs_pop_all_blocking: pop all nodes from a stack.
 206  *
 207  * Calls __cds_wfs_pop_all with an internal pop mutex held.
 208  */
 209 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
 210
 211 /*
 212  * cds_wfs_first: get first node of a popped stack.
 213  *
 214  * Content written into the node before enqueue is guaranteed to be
 215  * consistent, but no other memory ordering is ensured.
 216  *
 217  * Used by for-like iteration macros in urcu/wfstack.h:
 218  * cds_wfs_for_each_blocking()
 219  * cds_wfs_for_each_blocking_safe()
 220  *
 221  * Returns NULL if popped stack is empty, top stack node otherwise.
 222  */
 223 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
 224
 225 /*
 226  * cds_wfs_next_blocking: get next node of a popped stack.
 227  *
 228  * Content written into the node before enqueue is guaranteed to be
 229  * consistent, but no other memory ordering is ensured.
 230  *
 231  * Used by for-like iteration macros in urcu/wfstack.h:
 232  * cds_wfs_for_each_blocking()
 233  * cds_wfs_for_each_blocking_safe()
 234  *
 235  * Returns NULL if reached end of popped stack, non-NULL next stack
 236  * node otherwise.
 237  */
 238 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
 239
 240 /*
 241  * cds_wfs_next_nonblocking: get next node of a popped stack.
 242  *
 243  * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
 244  * needs to block.
 245  */
 246 extern struct cds_wfs_node *cds_wfs_next_nonblocking(struct cds_wfs_node *node);
 247
 248 /*
 249  * cds_wfs_pop_lock: lock stack pop-protection mutex.
 250  */
 251 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
 252
 253 /*
 254  * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 255  */
 256 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
 257
 258 /*
 259  * __cds_wfs_pop_blocking: pop a node from the stack.
 260  *
 261  * Returns NULL if stack is empty.
 262  *
 263  * __cds_wfs_pop_blocking needs to be synchronized using one of the
 264  * following techniques:
 265  *
 266  * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
 267  *    section. The caller must wait for a grace period to pass before
 268  *    freeing the returned node or modifying the cds_wfs_node structure.
 269  * 2) Using mutual exclusion (e.g. mutexes) to protect
 270  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 271  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 272  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 273  */
 274 extern struct cds_wfs_node *__cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack);
 275
 276 /*
 277  * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 278  *
 279  * Same as __cds_wfs_pop_blocking, but stores whether the stack was
 280  * empty into state (CDS_WFS_STATE_LAST).
 281  */
 282 extern struct cds_wfs_node *
 283         __cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack,
 284                 int *state);
 285
 286 /*
 287  * __cds_wfs_pop_nonblocking: pop a node from the stack.
 288  *
 289  * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
 290  * it needs to block.
 291  */
 292 extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack);
 293
 294 /*
 295  * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
 296  *
 297  * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
 298  * empty into state (CDS_WFS_STATE_LAST).
 299  */
 300 extern struct cds_wfs_node *
 301         __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack,
 302                 int *state);
 303
 304 /*
 305  * __cds_wfs_pop_all: pop all nodes from a stack.
 306  *
 307  * __cds_wfs_pop_all does not require any synchronization with other
 308  * push, nor with other __cds_wfs_pop_all, but requires synchronization
 309  * matching the technique used to synchronize __cds_wfs_pop_blocking:
 310  *
 311  * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
 312  *    section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
 313  *    must wait for a grace period to pass before freeing the returned
 314  *    node or modifying the cds_wfs_node structure. However, no RCU
 315  *    read-side critical section is needed around __cds_wfs_pop_all.
 316  * 2) Using mutual exclusion (e.g. mutexes) to protect
 317  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 318  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 319  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 320  */
 321 extern struct cds_wfs_head *__cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack);
 322
 323 #endif /* !_LGPL_SOURCE */
 324
 325 /*
 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).
 330  *
 331  * Content written into each node before enqueue is guaranteed to be
 332  * consistent, but no other memory ordering is ensured.
 333  */
 334 #define cds_wfs_for_each_blocking(head, node)                   \
 335         for (node = cds_wfs_first(head);                        \
 336                 node != NULL;                                   \
 337                 node = cds_wfs_next_blocking(node))
 338
 339 /*
 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
 345  *     internally).
 346  *
 347  * Content written into each node before enqueue is guaranteed to be
 348  * consistent, but no other memory ordering is ensured.
 349  */
 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);   \
 353                 node != NULL;                                              \
 354                 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
 355
 356 #ifdef __cplusplus
 357 }
 358
 359 /*
 360  * In C++, implement static inline wrappers using function overloading
 361  * to obtain an API similar to C.
 362  */
 363
 364 static inline cds_wfs_stack_ptr_t cds_wfs_stack_cast(struct __cds_wfs_stack *s)
 365 {
 366         cds_wfs_stack_ptr_t ret = {
 367                 ._s = s,
 368         };
 369         return ret;
 370 }
 371
 372 static inline cds_wfs_stack_ptr_t cds_wfs_stack_cast(struct cds_wfs_stack *s)
 373 {
 374         cds_wfs_stack_ptr_t ret = {
 375                 .s = s,
 376         };
 377         return ret;
 378 }
 379
 380 static inline cds_wfs_stack_const_ptr_t cds_wfs_stack_const_cast(const struct __cds_wfs_stack *s)
 381 {
 382         cds_wfs_stack_const_ptr_t ret = {
 383                 ._s = s,
 384         };
 385         return ret;
 386 }
 387
 388 static inline cds_wfs_stack_const_ptr_t cds_wfs_stack_const_cast(const struct cds_wfs_stack *s)
 389 {
 390         cds_wfs_stack_const_ptr_t ret = {
 391                 .s = s,
 392         };
 393         return ret;
 394 }
 395
 396 template<typename T> static inline bool cds_wfs_empty(T s)
 397 {
 398         return cds_wfs_empty(cds_wfs_stack_const_cast(s));
 399 }
 400
 401 template<typename T> static inline int cds_wfs_push(T s, struct cds_wfs_node *node)
 402 {
 403         return cds_wfs_push(cds_wfs_stack_cast(s), node);
 404 }
 405
 406 template<typename T> static inline struct cds_wfs_node *__cds_wfs_pop_blocking(T s)
 407 {
 408         return __cds_wfs_pop_blocking(cds_wfs_stack_cast(s));
 409 }
 410
 411 template<typename T> static inline struct cds_wfs_node *
 412         __cds_wfs_pop_with_state_blocking(T s, int *state)
 413 {
 414         return __cds_wfs_pop_with_state_blocking(cds_wfs_stack_cast(s), state);
 415 }
 416
 417 template<typename T> static inline struct cds_wfs_node *__cds_wfs_pop_nonblocking(T s)
 418
 419 {
 420         return __cds_wfs_pop_nonblocking(cds_wfs_stack_cast(s));
 421 }
 422
 423 template<typename T> static inline struct cds_wfs_node *
 424         __cds_wfs_pop_with_state_nonblocking(T s, int *state)
 425 {
 426         return __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_cast(s), state);
 427 }
 428
 429 template<typename T> static inline struct cds_wfs_head *__cds_wfs_pop_all(T s)
 430 {
 431         return __cds_wfs_pop_all(cds_wfs_stack_cast(s));
 432 }
 433
 434 #endif
 435
 436 #endif /* _URCU_WFSTACK_H */