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