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 };
  89
  90 struct cds_wfs_stack {
  91         struct cds_wfs_head *head;
  92         pthread_mutex_t lock;
  93 };
  94
  95 /*
  96  * The transparent union allows calling functions that work on both
  97  * struct cds_wfs_stack and struct __cds_wfs_stack on any of those two
  98  * types.
  99  */
 100 typedef union {
 101         struct __cds_wfs_stack *_s;
 102         struct cds_wfs_stack *s;
 103 } __attribute__((__transparent_union__)) cds_wfs_stack_ptr_t;
 104
 105 #ifdef _LGPL_SOURCE
 106
 107 #include <urcu/static/wfstack.h>
 108
 109 #define cds_wfs_node_init               _cds_wfs_node_init
 110 #define cds_wfs_init                    _cds_wfs_init
 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.
 150  */
 151 extern void cds_wfs_init(struct cds_wfs_stack *s);
 152
 153 /*
 154  * __cds_wfs_init: initialize wait-free stack.
 155  */
 156 extern void __cds_wfs_init(struct __cds_wfs_stack *s);
 157
 158 /*
 159  * cds_wfs_empty: return whether wait-free stack is empty.
 160  *
 161  * No memory barrier is issued. No mutual exclusion is required.
 162  */
 163 extern bool cds_wfs_empty(cds_wfs_stack_ptr_t u_stack);
 164
 165 /*
 166  * cds_wfs_push: push a node into the stack.
 167  *
 168  * Issues a full memory barrier before push. No mutual exclusion is
 169  * required.
 170  *
 171  * Returns 0 if the stack was empty prior to adding the node.
 172  * Returns non-zero otherwise.
 173  */
 174 extern int cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node);
 175
 176 /*
 177  * cds_wfs_pop_blocking: pop a node from the stack.
 178  *
 179  * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
 180  */
 181 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 182
 183 /*
 184  * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 185  *
 186  * Same as cds_wfs_pop_blocking, but stores whether the stack was
 187  * empty into state (CDS_WFS_STATE_LAST).
 188  */
 189 extern struct cds_wfs_node *
 190         cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
 191
 192 /*
 193  * cds_wfs_pop_all_blocking: pop all nodes from a stack.
 194  *
 195  * Calls __cds_wfs_pop_all with an internal pop mutex held.
 196  */
 197 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
 198
 199 /*
 200  * cds_wfs_first: get first node of a popped stack.
 201  *
 202  * Content written into the node before enqueue is guaranteed to be
 203  * consistent, but no other memory ordering is ensured.
 204  *
 205  * Used by for-like iteration macros in urcu/wfstack.h:
 206  * cds_wfs_for_each_blocking()
 207  * cds_wfs_for_each_blocking_safe()
 208  *
 209  * Returns NULL if popped stack is empty, top stack node otherwise.
 210  */
 211 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
 212
 213 /*
 214  * cds_wfs_next_blocking: get next node of a popped stack.
 215  *
 216  * Content written into the node before enqueue is guaranteed to be
 217  * consistent, but no other memory ordering is ensured.
 218  *
 219  * Used by for-like iteration macros in urcu/wfstack.h:
 220  * cds_wfs_for_each_blocking()
 221  * cds_wfs_for_each_blocking_safe()
 222  *
 223  * Returns NULL if reached end of popped stack, non-NULL next stack
 224  * node otherwise.
 225  */
 226 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
 227
 228 /*
 229  * cds_wfs_next_nonblocking: get next node of a popped stack.
 230  *
 231  * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
 232  * needs to block.
 233  */
 234 extern struct cds_wfs_node *cds_wfs_next_nonblocking(struct cds_wfs_node *node);
 235
 236 /*
 237  * cds_wfs_pop_lock: lock stack pop-protection mutex.
 238  */
 239 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
 240
 241 /*
 242  * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 243  */
 244 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
 245
 246 /*
 247  * __cds_wfs_pop_blocking: pop a node from the stack.
 248  *
 249  * Returns NULL if stack is empty.
 250  *
 251  * __cds_wfs_pop_blocking needs to be synchronized using one of the
 252  * following techniques:
 253  *
 254  * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
 255  *    section. The caller must wait for a grace period to pass before
 256  *    freeing the returned node or modifying the cds_wfs_node structure.
 257  * 2) Using mutual exclusion (e.g. mutexes) to protect
 258  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 259  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 260  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 261  */
 262 extern struct cds_wfs_node *__cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack);
 263
 264 /*
 265  * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 266  *
 267  * Same as __cds_wfs_pop_blocking, but stores whether the stack was
 268  * empty into state (CDS_WFS_STATE_LAST).
 269  */
 270 extern struct cds_wfs_node *
 271         __cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack,
 272                 int *state);
 273
 274 /*
 275  * __cds_wfs_pop_nonblocking: pop a node from the stack.
 276  *
 277  * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
 278  * it needs to block.
 279  */
 280 extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack);
 281
 282 /*
 283  * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
 284  *
 285  * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
 286  * empty into state (CDS_WFS_STATE_LAST).
 287  */
 288 extern struct cds_wfs_node *
 289         __cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack,
 290                 int *state);
 291
 292 /*
 293  * __cds_wfs_pop_all: pop all nodes from a stack.
 294  *
 295  * __cds_wfs_pop_all does not require any synchronization with other
 296  * push, nor with other __cds_wfs_pop_all, but requires synchronization
 297  * matching the technique used to synchronize __cds_wfs_pop_blocking:
 298  *
 299  * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
 300  *    section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
 301  *    must wait for a grace period to pass before freeing the returned
 302  *    node or modifying the cds_wfs_node structure. However, no RCU
 303  *    read-side critical section is needed around __cds_wfs_pop_all.
 304  * 2) Using mutual exclusion (e.g. mutexes) to protect
 305  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 306  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 307  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 308  */
 309 extern struct cds_wfs_head *__cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack);
 310
 311 #endif /* !_LGPL_SOURCE */
 312
 313 #ifdef __cplusplus
 314 }
 315 #endif
 316
 317 /*
 318  * cds_wfs_for_each_blocking: Iterate over all nodes returned by
 319  * __cds_wfs_pop_all().
 320  * @head: head of the queue (struct cds_wfs_head pointer).
 321  * @node: iterator (struct cds_wfs_node pointer).
 322  *
 323  * Content written into each node before enqueue is guaranteed to be
 324  * consistent, but no other memory ordering is ensured.
 325  */
 326 #define cds_wfs_for_each_blocking(head, node)                   \
 327         for (node = cds_wfs_first(head);                        \
 328                 node != NULL;                                   \
 329                 node = cds_wfs_next_blocking(node))
 330
 331 /*
 332  * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
 333  * __cds_wfs_pop_all(). Safe against deletion.
 334  * @head: head of the queue (struct cds_wfs_head pointer).
 335  * @node: iterator (struct cds_wfs_node pointer).
 336  * @n: struct cds_wfs_node pointer holding the next pointer (used
 337  *     internally).
 338  *
 339  * Content written into each node before enqueue is guaranteed to be
 340  * consistent, but no other memory ordering is ensured.
 341  */
 342 #define cds_wfs_for_each_blocking_safe(head, node, n)                      \
 343         for (node = cds_wfs_first(head),                                   \
 344                         n = (node ? cds_wfs_next_blocking(node) : NULL);   \
 345                 node != NULL;                                              \
 346                 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
 347
 348 #endif /* _URCU_WFSTACK_H */