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 <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_destroy                 _cds_wfs_destroy
  98 #define cds_wfs_empty                   _cds_wfs_empty
  99 #define cds_wfs_push                    _cds_wfs_push
 100
 101 /* Locking performed internally */
 102 #define cds_wfs_pop_blocking            _cds_wfs_pop_blocking
 103 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
 104 #define cds_wfs_pop_all_blocking        _cds_wfs_pop_all_blocking
 105
 106 /*
 107  * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
 108  * cds_wfs_pop_all_blocking.
 109  */
 110 #define cds_wfs_first                   _cds_wfs_first
 111 #define cds_wfs_next_blocking           _cds_wfs_next_blocking
 112 #define cds_wfs_next_nonblocking        _cds_wfs_next_nonblocking
 113
 114 /* Pop locking with internal mutex */
 115 #define cds_wfs_pop_lock                _cds_wfs_pop_lock
 116 #define cds_wfs_pop_unlock              _cds_wfs_pop_unlock
 117
 118 /* Synchronization ensured by the caller. See synchronization table. */
 119 #define __cds_wfs_pop_blocking          ___cds_wfs_pop_blocking
 120 #define __cds_wfs_pop_with_state_blocking       \
 121                                         ___cds_wfs_pop_with_state_blocking
 122 #define __cds_wfs_pop_nonblocking       ___cds_wfs_pop_nonblocking
 123 #define __cds_wfs_pop_with_state_nonblocking    \
 124                                         ___cds_wfs_pop_with_state_nonblocking
 125 #define __cds_wfs_pop_all               ___cds_wfs_pop_all
 126
 127 #else /* !_LGPL_SOURCE */
 128
 129 /*
 130  * cds_wfs_node_init: initialize wait-free stack node.
 131  */
 132 extern void cds_wfs_node_init(struct cds_wfs_node *node);
 133
 134 /*
 135  * cds_wfs_init: initialize wait-free stack (with lock). Pair with
 136  * cds_wfs_destroy().
 137  */
 138 extern void cds_wfs_init(struct cds_wfs_stack *s);
 139
 140 /*
 141  * cds_wfs_destroy: destroy wait-free stack (with lock). Pair with
 142  * cds_wfs_init().
 143  */
 144 extern void cds_wfs_destroy(struct cds_wfs_stack *s);
 145
 146 /*
 147  * cds_wfs_empty: return whether wait-free stack is empty.
 148  *
 149  * No memory barrier is issued. No mutual exclusion is required.
 150  */
 151 extern bool cds_wfs_empty(struct cds_wfs_stack *s);
 152
 153 /*
 154  * cds_wfs_push: push a node into the stack.
 155  *
 156  * Issues a full memory barrier before push. No mutual exclusion is
 157  * required.
 158  *
 159  * Returns 0 if the stack was empty prior to adding the node.
 160  * Returns non-zero otherwise.
 161  */
 162 extern int cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node);
 163
 164 /*
 165  * cds_wfs_pop_blocking: pop a node from the stack.
 166  *
 167  * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
 168  */
 169 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 170
 171 /*
 172  * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 173  *
 174  * Same as cds_wfs_pop_blocking, but stores whether the stack was
 175  * empty into state (CDS_WFS_STATE_LAST).
 176  */
 177 extern struct cds_wfs_node *
 178         cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
 179
 180 /*
 181  * cds_wfs_pop_all_blocking: pop all nodes from a stack.
 182  *
 183  * Calls __cds_wfs_pop_all with an internal pop mutex held.
 184  */
 185 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
 186
 187 /*
 188  * cds_wfs_first: get first node of a popped stack.
 189  *
 190  * Content written into the node before enqueue is guaranteed to be
 191  * consistent, but no other memory ordering is ensured.
 192  *
 193  * Used by for-like iteration macros in urcu/wfstack.h:
 194  * cds_wfs_for_each_blocking()
 195  * cds_wfs_for_each_blocking_safe()
 196  *
 197  * Returns NULL if popped stack is empty, top stack node otherwise.
 198  */
 199 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
 200
 201 /*
 202  * cds_wfs_next_blocking: get next node of a popped stack.
 203  *
 204  * Content written into the node before enqueue is guaranteed to be
 205  * consistent, but no other memory ordering is ensured.
 206  *
 207  * Used by for-like iteration macros in urcu/wfstack.h:
 208  * cds_wfs_for_each_blocking()
 209  * cds_wfs_for_each_blocking_safe()
 210  *
 211  * Returns NULL if reached end of popped stack, non-NULL next stack
 212  * node otherwise.
 213  */
 214 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
 215
 216 /*
 217  * cds_wfs_next_nonblocking: get next node of a popped stack.
 218  *
 219  * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
 220  * needs to block.
 221  */
 222 extern struct cds_wfs_node *cds_wfs_next_nonblocking(struct cds_wfs_node *node);
 223
 224 /*
 225  * cds_wfs_pop_lock: lock stack pop-protection mutex.
 226  */
 227 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
 228
 229 /*
 230  * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 231  */
 232 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
 233
 234 /*
 235  * __cds_wfs_pop_blocking: pop a node from the stack.
 236  *
 237  * Returns NULL if stack is empty.
 238  *
 239  * __cds_wfs_pop_blocking needs to be synchronized using one of the
 240  * following techniques:
 241  *
 242  * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
 243  *    section. The caller must wait for a grace period to pass before
 244  *    freeing the returned node or modifying the cds_wfs_node structure.
 245  * 2) Using mutual exclusion (e.g. mutexes) to protect
 246  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 247  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 248  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 249  */
 250 extern struct cds_wfs_node *__cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 251
 252 /*
 253  * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 254  *
 255  * Same as __cds_wfs_pop_blocking, but stores whether the stack was
 256  * empty into state (CDS_WFS_STATE_LAST).
 257  */
 258 extern struct cds_wfs_node *
 259         __cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
 260
 261 /*
 262  * __cds_wfs_pop_nonblocking: pop a node from the stack.
 263  *
 264  * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
 265  * it needs to block.
 266  */
 267 extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(struct cds_wfs_stack *s);
 268
 269 /*
 270  * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
 271  *
 272  * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
 273  * empty into state (CDS_WFS_STATE_LAST).
 274  */
 275 extern struct cds_wfs_node *
 276         __cds_wfs_pop_with_state_nonblocking(struct cds_wfs_stack *s,
 277                 int *state);
 278
 279 /*
 280  * __cds_wfs_pop_all: pop all nodes from a stack.
 281  *
 282  * __cds_wfs_pop_all does not require any synchronization with other
 283  * push, nor with other __cds_wfs_pop_all, but requires synchronization
 284  * matching the technique used to synchronize __cds_wfs_pop_blocking:
 285  *
 286  * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
 287  *    section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
 288  *    must wait for a grace period to pass before freeing the returned
 289  *    node or modifying the cds_wfs_node structure. However, no RCU
 290  *    read-side critical section is needed around __cds_wfs_pop_all.
 291  * 2) Using mutual exclusion (e.g. mutexes) to protect
 292  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 293  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 294  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 295  */
 296 extern struct cds_wfs_head *__cds_wfs_pop_all(struct cds_wfs_stack *s);
 297
 298 #endif /* !_LGPL_SOURCE */
 299
 300 #ifdef __cplusplus
 301 }
 302 #endif
 303
 304 /*
 305  * cds_wfs_for_each_blocking: Iterate over all nodes returned by
 306  * __cds_wfs_pop_all().
 307  * @head: head of the queue (struct cds_wfs_head pointer).
 308  * @node: iterator (struct cds_wfs_node pointer).
 309  *
 310  * Content written into each node before enqueue is guaranteed to be
 311  * consistent, but no other memory ordering is ensured.
 312  */
 313 #define cds_wfs_for_each_blocking(head, node)                   \
 314         for (node = cds_wfs_first(head);                        \
 315                 node != NULL;                                   \
 316                 node = cds_wfs_next_blocking(node))
 317
 318 /*
 319  * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
 320  * __cds_wfs_pop_all(). Safe against deletion.
 321  * @head: head of the queue (struct cds_wfs_head pointer).
 322  * @node: iterator (struct cds_wfs_node pointer).
 323  * @n: struct cds_wfs_node pointer holding the next pointer (used
 324  *     internally).
 325  *
 326  * Content written into each node before enqueue is guaranteed to be
 327  * consistent, but no other memory ordering is ensured.
 328  */
 329 #define cds_wfs_for_each_blocking_safe(head, node, n)                      \
 330         for (node = cds_wfs_first(head),                                   \
 331                         n = (node ? cds_wfs_next_blocking(node) : NULL);   \
 332                 node != NULL;                                              \
 333                 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
 334
 335 #endif /* _URCU_WFSTACK_H */