include/urcu/wfstack.h

   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 <stdbool.h>
  28 #include <urcu/compiler.h>
  29
  30 #ifdef __cplusplus
  31 extern "C" {
  32 #endif
  33
  34 /*
  35  * Stack with wait-free push, blocking traversal.
  36  *
  37  * Stack implementing push, pop, pop_all operations, as well as iterator
  38  * on the stack head returned by pop_all.
  39  *
  40  * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
  41  *                       cds_wfs_first.
  42  * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
  43  *                      iteration on stack head returned by pop_all.
  44  *
  45  * Synchronization table:
  46  *
  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 "-".
  50  *
  51  *                      cds_wfs_push  __cds_wfs_pop  __cds_wfs_pop_all
  52  * cds_wfs_push               -              -                  -
  53  * __cds_wfs_pop              -              X                  X
  54  * __cds_wfs_pop_all          -              X                  -
  55  *
  56  * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
  57  * synchronization.
  58  */
  59
  60 #define CDS_WFS_WOULDBLOCK      ((struct cds_wfs_node *) -1UL)
  61
  62 enum cds_wfs_state {
  63         CDS_WFS_STATE_LAST =            (1U << 0),
  64 };
  65
  66 /*
  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.
  70  */
  71 struct cds_wfs_node {
  72         struct cds_wfs_node *next;
  73 };
  74
  75 /*
  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
  79  * types.
  80  */
  81 struct cds_wfs_head {
  82         struct cds_wfs_node node;
  83 };
  84
  85 struct __cds_wfs_stack {
  86         struct cds_wfs_head *head;
  87 };
  88
  89 struct cds_wfs_stack {
  90         struct cds_wfs_head *head;
  91         pthread_mutex_t lock;
  92 };
  93
  94 /*
  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
  97  * types.
  98  *
  99  * Avoid complaints from clang++ not knowing this attribute.
 100  */
 101 typedef union {
 102         struct __cds_wfs_stack *_s;
 103         struct cds_wfs_stack *s;
 104 } caa_c_transparent_union cds_wfs_stack_ptr_t;
 105
 106 #ifdef _LGPL_SOURCE
 107
 108 #include <urcu/static/wfstack.h>
 109
 110 #define cds_wfs_node_init               _cds_wfs_node_init
 111 #define cds_wfs_init                    _cds_wfs_init
 112 #define cds_wfs_destroy                 _cds_wfs_destroy
 113 #define __cds_wfs_init                  ___cds_wfs_init
 114 #define cds_wfs_empty                   _cds_wfs_empty
 115 #define cds_wfs_push                    _cds_wfs_push
 116
 117 /* Locking performed internally */
 118 #define cds_wfs_pop_blocking            _cds_wfs_pop_blocking
 119 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
 120 #define cds_wfs_pop_all_blocking        _cds_wfs_pop_all_blocking
 121
 122 /*
 123  * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
 124  * cds_wfs_pop_all_blocking.
 125  */
 126 #define cds_wfs_first                   _cds_wfs_first
 127 #define cds_wfs_next_blocking           _cds_wfs_next_blocking
 128 #define cds_wfs_next_nonblocking        _cds_wfs_next_nonblocking
 129
 130 /* Pop locking with internal mutex */
 131 #define cds_wfs_pop_lock                _cds_wfs_pop_lock
 132 #define cds_wfs_pop_unlock              _cds_wfs_pop_unlock
 133
 134 /* Synchronization ensured by the caller. See synchronization table. */
 135 #define __cds_wfs_pop_blocking          ___cds_wfs_pop_blocking
 136 #define __cds_wfs_pop_with_state_blocking       \
 137                                         ___cds_wfs_pop_with_state_blocking
 138 #define __cds_wfs_pop_nonblocking       ___cds_wfs_pop_nonblocking
 139 #define __cds_wfs_pop_with_state_nonblocking    \
 140                                         ___cds_wfs_pop_with_state_nonblocking
 141 #define __cds_wfs_pop_all               ___cds_wfs_pop_all
 142
 143 #else /* !_LGPL_SOURCE */
 144
 145 /*
 146  * cds_wfs_node_init: initialize wait-free stack node.
 147  */
 148 extern void cds_wfs_node_init(struct cds_wfs_node *node);
 149
 150 /*
 151  * cds_wfs_init: initialize wait-free stack (with lock). Pair with
 152  * cds_wfs_destroy().
 153  */
 154 extern void cds_wfs_init(struct cds_wfs_stack *s);
 155
 156 /*
 157  * cds_wfs_destroy: destroy wait-free stack (with lock). Pair with
 158  * cds_wfs_init().
 159  */
 160 extern void cds_wfs_destroy(struct cds_wfs_stack *s);
 161
 162 /*
 163  * __cds_wfs_init: initialize wait-free stack (no lock). Don't pair with
 164  * any destroy function.
 165  */
 166 extern void __cds_wfs_init(struct __cds_wfs_stack *s);
 167
 168 /*
 169  * cds_wfs_empty: return whether wait-free stack is empty.
 170  *
 171  * No memory barrier is issued. No mutual exclusion is required.
 172  */
 173 extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack);
 174
 175 /*
 176  * cds_wfs_push: push a node into the stack.
 177  *
 178  * Issues a full memory barrier before push. No mutual exclusion is
 179  * required.
 180  *
 181  * Returns 0 if the stack was empty prior to adding the node.
 182  * Returns non-zero otherwise.
 183  */
 184 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node);
 185
 186 /*
 187  * cds_wfs_pop_blocking: pop a node from the stack.
 188  *
 189  * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
 190  */
 191 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 192
 193 /*
 194  * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 195  *
 196  * Same as cds_wfs_pop_blocking, but stores whether the stack was
 197  * empty into state (CDS_WFS_STATE_LAST).
 198  */
 199 extern struct cds_wfs_node *
 200         cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
 201
 202 /*
 203  * cds_wfs_pop_all_blocking: pop all nodes from a stack.
 204  *
 205  * Calls __cds_wfs_pop_all with an internal pop mutex held.
 206  */
 207 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
 208
 209 /*
 210  * cds_wfs_first: get first node of a popped stack.
 211  *
 212  * Content written into the node before enqueue is guaranteed to be
 213  * consistent, but no other memory ordering is ensured.
 214  *
 215  * Used by for-like iteration macros in urcu/wfstack.h:
 216  * cds_wfs_for_each_blocking()
 217  * cds_wfs_for_each_blocking_safe()
 218  *
 219  * Returns NULL if popped stack is empty, top stack node otherwise.
 220  */
 221 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
 222
 223 /*
 224  * cds_wfs_next_blocking: get next node of a popped stack.
 225  *
 226  * Content written into the node before enqueue is guaranteed to be
 227  * consistent, but no other memory ordering is ensured.
 228  *
 229  * Used by for-like iteration macros in urcu/wfstack.h:
 230  * cds_wfs_for_each_blocking()
 231  * cds_wfs_for_each_blocking_safe()
 232  *
 233  * Returns NULL if reached end of popped stack, non-NULL next stack
 234  * node otherwise.
 235  */
 236 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
 237
 238 /*
 239  * cds_wfs_next_nonblocking: get next node of a popped stack.
 240  *
 241  * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
 242  * needs to block.
 243  */
 244 extern struct cds_wfs_node *cds_wfs_next_nonblocking(struct cds_wfs_node *node);
 245
 246 /*
 247  * cds_wfs_pop_lock: lock stack pop-protection mutex.
 248  */
 249 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
 250
 251 /*
 252  * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 253  */
 254 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
 255
 256 /*
 257  * __cds_wfs_pop_blocking: pop a node from the stack.
 258  *
 259  * Returns NULL if stack is empty.
 260  *
 261  * __cds_wfs_pop_blocking needs to be synchronized using one of the
 262  * following techniques:
 263  *
 264  * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
 265  *    section. The caller must wait for a grace period to pass before
 266  *    freeing the returned node or modifying the cds_wfs_node structure.
 267  * 2) Using mutual exclusion (e.g. mutexes) to protect
 268  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 269  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 270  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 271  */
 272 extern struct cds_wfs_node *__cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack);
 273
 274 /*
 275  * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 276  *
 277  * Same as __cds_wfs_pop_blocking, but stores whether the stack was
 278  * empty into state (CDS_WFS_STATE_LAST).
 279  */
 280 extern struct cds_wfs_node *
 281         __cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack,
 282                 int *state);
 283
 284 /*
 285  * __cds_wfs_pop_nonblocking: pop a node from the stack.
 286  *
 287  * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
 288  * it needs to block.
 289  */
 290 extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack);
 291
 292 /*
 293  * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
 294  *
 295  * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
 296  * empty into state (CDS_WFS_STATE_LAST).
 297  */
 298 extern struct cds_wfs_node *
 299         __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack,
 300                 int *state);
 301
 302 /*
 303  * __cds_wfs_pop_all: pop all nodes from a stack.
 304  *
 305  * __cds_wfs_pop_all does not require any synchronization with other
 306  * push, nor with other __cds_wfs_pop_all, but requires synchronization
 307  * matching the technique used to synchronize __cds_wfs_pop_blocking:
 308  *
 309  * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
 310  *    section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
 311  *    must wait for a grace period to pass before freeing the returned
 312  *    node or modifying the cds_wfs_node structure. However, no RCU
 313  *    read-side critical section is needed around __cds_wfs_pop_all.
 314  * 2) Using mutual exclusion (e.g. mutexes) to protect
 315  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 316  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 317  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 318  */
 319 extern struct cds_wfs_head *__cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack);
 320
 321 #endif /* !_LGPL_SOURCE */
 322
 323 #ifdef __cplusplus
 324 }
 325 #endif
 326
 327 /*
 328  * cds_wfs_for_each_blocking: Iterate over all nodes returned by
 329  * __cds_wfs_pop_all().
 330  * @head: head of the queue (struct cds_wfs_head pointer).
 331  * @node: iterator (struct cds_wfs_node pointer).
 332  *
 333  * Content written into each node before enqueue is guaranteed to be
 334  * consistent, but no other memory ordering is ensured.
 335  */
 336 #define cds_wfs_for_each_blocking(head, node)                   \
 337         for (node = cds_wfs_first(head);                        \
 338                 node != NULL;                                   \
 339                 node = cds_wfs_next_blocking(node))
 340
 341 /*
 342  * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
 343  * __cds_wfs_pop_all(). Safe against deletion.
 344  * @head: head of the queue (struct cds_wfs_head pointer).
 345  * @node: iterator (struct cds_wfs_node pointer).
 346  * @n: struct cds_wfs_node pointer holding the next pointer (used
 347  *     internally).
 348  *
 349  * Content written into each node before enqueue is guaranteed to be
 350  * consistent, but no other memory ordering is ensured.
 351  */
 352 #define cds_wfs_for_each_blocking_safe(head, node, n)                      \
 353         for (node = cds_wfs_first(head),                                   \
 354                         n = (node ? cds_wfs_next_blocking(node) : NULL);   \
 355                 node != NULL;                                              \
 356                 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
 357
 358 #endif /* _URCU_WFSTACK_H */