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      ((void *) -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 typedef union {
 100         struct __cds_wfs_stack *_s;
 101         struct cds_wfs_stack *s;
 102 } __attribute__((__transparent_union__)) cds_wfs_stack_ptr_t;
 103
 104 #ifdef _LGPL_SOURCE
 105
 106 #include <urcu/static/wfstack.h>
 107
 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
 114
 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
 119
 120 /*
 121  * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
 122  * cds_wfs_pop_all_blocking.
 123  */
 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
 127
 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
 131
 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
 140
 141 #else /* !_LGPL_SOURCE */
 142
 143 /*
 144  * cds_wfs_node_init: initialize wait-free stack node.
 145  */
 146 extern void cds_wfs_node_init(struct cds_wfs_node *node);
 147
 148 /*
 149  * cds_wfs_init: initialize wait-free stack (with lock). Pair with
 150  * cds_wfs_destroy().
 151  */
 152 extern void cds_wfs_init(struct cds_wfs_stack *s);
 153
 154 /*
 155  * cds_wfs_destroy: destroy wait-free stack (with lock). Pair with
 156  * cds_wfs_init().
 157  */
 158 extern void cds_wfs_destroy(struct cds_wfs_stack *s);
 159
 160 /*
 161  * __cds_wfs_init: initialize wait-free stack (no lock). Don't pair with
 162  * any destroy function.
 163  */
 164 extern void __cds_wfs_init(struct __cds_wfs_stack *s);
 165
 166 /*
 167  * cds_wfs_empty: return whether wait-free stack is empty.
 168  *
 169  * No memory barrier is issued. No mutual exclusion is required.
 170  */
 171 extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack);
 172
 173 /*
 174  * cds_wfs_push: push a node into the stack.
 175  *
 176  * Issues a full memory barrier before push. No mutual exclusion is
 177  * required.
 178  *
 179  * Returns 0 if the stack was empty prior to adding the node.
 180  * Returns non-zero otherwise.
 181  */
 182 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node);
 183
 184 /*
 185  * cds_wfs_pop_blocking: pop a node from the stack.
 186  *
 187  * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
 188  */
 189 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 190
 191 /*
 192  * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 193  *
 194  * Same as cds_wfs_pop_blocking, but stores whether the stack was
 195  * empty into state (CDS_WFS_STATE_LAST).
 196  */
 197 extern struct cds_wfs_node *
 198         cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
 199
 200 /*
 201  * cds_wfs_pop_all_blocking: pop all nodes from a stack.
 202  *
 203  * Calls __cds_wfs_pop_all with an internal pop mutex held.
 204  */
 205 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
 206
 207 /*
 208  * cds_wfs_first: get first node of a popped stack.
 209  *
 210  * Content written into the node before enqueue is guaranteed to be
 211  * consistent, but no other memory ordering is ensured.
 212  *
 213  * Used by for-like iteration macros in urcu/wfstack.h:
 214  * cds_wfs_for_each_blocking()
 215  * cds_wfs_for_each_blocking_safe()
 216  *
 217  * Returns NULL if popped stack is empty, top stack node otherwise.
 218  */
 219 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
 220
 221 /*
 222  * cds_wfs_next_blocking: get next node of a popped stack.
 223  *
 224  * Content written into the node before enqueue is guaranteed to be
 225  * consistent, but no other memory ordering is ensured.
 226  *
 227  * Used by for-like iteration macros in urcu/wfstack.h:
 228  * cds_wfs_for_each_blocking()
 229  * cds_wfs_for_each_blocking_safe()
 230  *
 231  * Returns NULL if reached end of popped stack, non-NULL next stack
 232  * node otherwise.
 233  */
 234 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
 235
 236 /*
 237  * cds_wfs_next_nonblocking: get next node of a popped stack.
 238  *
 239  * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
 240  * needs to block.
 241  */
 242 extern struct cds_wfs_node *cds_wfs_next_nonblocking(struct cds_wfs_node *node);
 243
 244 /*
 245  * cds_wfs_pop_lock: lock stack pop-protection mutex.
 246  */
 247 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
 248
 249 /*
 250  * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 251  */
 252 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
 253
 254 /*
 255  * __cds_wfs_pop_blocking: pop a node from the stack.
 256  *
 257  * Returns NULL if stack is empty.
 258  *
 259  * __cds_wfs_pop_blocking needs to be synchronized using one of the
 260  * following techniques:
 261  *
 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).
 269  */
 270 extern struct cds_wfs_node *__cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack);
 271
 272 /*
 273  * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 274  *
 275  * Same as __cds_wfs_pop_blocking, but stores whether the stack was
 276  * empty into state (CDS_WFS_STATE_LAST).
 277  */
 278 extern struct cds_wfs_node *
 279         __cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack,
 280                 int *state);
 281
 282 /*
 283  * __cds_wfs_pop_nonblocking: pop a node from the stack.
 284  *
 285  * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
 286  * it needs to block.
 287  */
 288 extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack);
 289
 290 /*
 291  * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
 292  *
 293  * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
 294  * empty into state (CDS_WFS_STATE_LAST).
 295  */
 296 extern struct cds_wfs_node *
 297         __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack,
 298                 int *state);
 299
 300 /*
 301  * __cds_wfs_pop_all: pop all nodes from a stack.
 302  *
 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:
 306  *
 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).
 316  */
 317 extern struct cds_wfs_head *__cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack);
 318
 319 #endif /* !_LGPL_SOURCE */
 320
 321 #ifdef __cplusplus
 322 }
 323 #endif
 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 #endif /* _URCU_WFSTACK_H */