bsd/sys/queue.h

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*
  29  * Copyright (c) 1991, 1993
  30  *      The Regents of the University of California.  All rights reserved.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 3. All advertising materials mentioning features or use of this software
  41  *    must display the following acknowledgement:
  42  *      This product includes software developed by the University of
  43  *      California, Berkeley and its contributors.
  44  * 4. Neither the name of the University nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  *
  60  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  61  */
  62
  63 #ifndef _SYS_QUEUE_H_
  64 #define _SYS_QUEUE_H_
  65
  66 /*
  67  * This file defines five types of data structures: singly-linked lists,
  68  * slingly-linked tail queues, lists, tail queues, and circular queues.
  69  *
  70  * A singly-linked list is headed by a single forward pointer. The elements
  71  * are singly linked for minimum space and pointer manipulation overhead at
  72  * the expense of O(n) removal for arbitrary elements. New elements can be
  73  * added to the list after an existing element or at the head of the list.
  74  * Elements being removed from the head of the list should use the explicit
  75  * macro for this purpose for optimum efficiency. A singly-linked list may
  76  * only be traversed in the forward direction.  Singly-linked lists are ideal
  77  * for applications with large datasets and few or no removals or for
  78  * implementing a LIFO queue.
  79  *
  80  * A singly-linked tail queue is headed by a pair of pointers, one to the
  81  * head of the list and the other to the tail of the list. The elements are
  82  * singly linked for minimum space and pointer manipulation overhead at the
  83  * expense of O(n) removal for arbitrary elements. New elements can be added
  84  * to the list after an existing element, at the head of the list, or at the
  85  * end of the list. Elements being removed from the head of the tail queue
  86  * should use the explicit macro for this purpose for optimum efficiency.
  87  * A singly-linked tail queue may only be traversed in the forward direction.
  88  * Singly-linked tail queues are ideal for applications with large datasets
  89  * and few or no removals or for implementing a FIFO queue.
  90  *
  91  * A list is headed by a single forward pointer (or an array of forward
  92  * pointers for a hash table header). The elements are doubly linked
  93  * so that an arbitrary element can be removed without a need to
  94  * traverse the list. New elements can be added to the list before
  95  * or after an existing element or at the head of the list. A list
  96  * may only be traversed in the forward direction.
  97  *
  98  * A tail queue is headed by a pair of pointers, one to the head of the
  99  * list and the other to the tail of the list. The elements are doubly
 100  * linked so that an arbitrary element can be removed without a need to
 101  * traverse the list. New elements can be added to the list before or
 102  * after an existing element, at the head of the list, or at the end of
 103  * the list. A tail queue may only be traversed in the forward direction.
 104  *
 105  * A circle queue is headed by a pair of pointers, one to the head of the
 106  * list and the other to the tail of the list. The elements are doubly
 107  * linked so that an arbitrary element can be removed without a need to
 108  * traverse the list. New elements can be added to the list before or after
 109  * an existing element, at the head of the list, or at the end of the list.
 110  * A circle queue may be traversed in either direction, but has a more
 111  * complex end of list detection.
 112  *
 113  * For details on the use of these macros, see the queue(3) manual page.
 114  *
 115  *
 116  *                      SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
 117  * _HEAD                +       +       +       +       +
 118  * _ENTRY               +       +       +       +       +
 119  * _INIT                +       +       +       +       +
 120  * _EMPTY               +       +       +       +       +
 121  * _FIRST               +       +       +       +       +
 122  * _NEXT                +       +       +       +       +
 123  * _PREV                -       -       -       +       +
 124  * _LAST                -       -       +       +       +
 125  * _FOREACH             +       +       -       +       +
 126  * _INSERT_HEAD         +       +       +       +       +
 127  * _INSERT_BEFORE       -       +       -       +       +
 128  * _INSERT_AFTER        +       +       +       +       +
 129  * _INSERT_TAIL         -       -       +       +       +
 130  * _REMOVE_HEAD         +       -       +       -       -
 131  * _REMOVE              +       +       +       +       +
 132  *
 133  */
 134
 135 /*
 136  * Singly-linked List definitions.
 137  */
 138 #define SLIST_HEAD(name, type)                                          \
 139 struct name {                                                           \
 140         struct type *slh_first; /* first element */                     \
 141 }
 142
 143 #define SLIST_ENTRY(type)                                               \
 144 struct {                                                                \
 145         struct type *sle_next;  /* next element */                      \
 146 }
 147
 148 /*
 149  * Singly-linked List functions.
 150  */
 151 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 152
 153 #define SLIST_FIRST(head)       ((head)->slh_first)
 154
 155 #define SLIST_FOREACH(var, head, field)                                 \
 156         for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
 157
 158 #define SLIST_INIT(head) {                                              \
 159         (head)->slh_first = NULL;                                       \
 160 }
 161
 162 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 163         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
 164         (slistelm)->field.sle_next = (elm);                             \
 165 } while (0)
 166
 167 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 168         (elm)->field.sle_next = (head)->slh_first;                      \
 169         (head)->slh_first = (elm);                                      \
 170 } while (0)
 171
 172 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 173
 174 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 175         (head)->slh_first = (head)->slh_first->field.sle_next;          \
 176 } while (0)
 177
 178 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 179         if ((head)->slh_first == (elm)) {                               \
 180                 SLIST_REMOVE_HEAD((head), field);                       \
 181         }                                                               \
 182         else {                                                          \
 183                 struct type *curelm = (head)->slh_first;                \
 184                 while( curelm->field.sle_next != (elm) )                \
 185                         curelm = curelm->field.sle_next;                \
 186                 curelm->field.sle_next =                                \
 187                     curelm->field.sle_next->field.sle_next;             \
 188         }                                                               \
 189 } while (0)
 190
 191 /*
 192  * Singly-linked Tail queue definitions.
 193  */
 194 #define STAILQ_HEAD(name, type)                                         \
 195 struct name {                                                           \
 196         struct type *stqh_first;/* first element */                     \
 197         struct type **stqh_last;/* addr of last next element */         \
 198 }
 199
 200 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 201         { NULL, &(head).stqh_first }
 202
 203 #define STAILQ_ENTRY(type)                                              \
 204 struct {                                                                \
 205         struct type *stqe_next; /* next element */                      \
 206 }
 207
 208 /*
 209  * Singly-linked Tail queue functions.
 210  */
 211 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
 212
 213 #define STAILQ_INIT(head) do {                                          \
 214         (head)->stqh_first = NULL;                                      \
 215         (head)->stqh_last = &(head)->stqh_first;                        \
 216 } while (0)
 217
 218 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 219 #define STAILQ_LAST(head)       (*(head)->stqh_last)
 220
 221 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 222         if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)      \
 223                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 224         (head)->stqh_first = (elm);                                     \
 225 } while (0)
 226
 227 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 228         (elm)->field.stqe_next = NULL;                                  \
 229         *(head)->stqh_last = (elm);                                     \
 230         (head)->stqh_last = &(elm)->field.stqe_next;                    \
 231 } while (0)
 232
 233 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 234         if (((elm)->field.stqe_next = (tqelm)->field.stqe_next) == NULL)\
 235                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 236         (tqelm)->field.stqe_next = (elm);                               \
 237 } while (0)
 238
 239 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 240
 241 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 242         if (((head)->stqh_first =                                       \
 243              (head)->stqh_first->field.stqe_next) == NULL)              \
 244                 (head)->stqh_last = &(head)->stqh_first;                \
 245 } while (0)
 246
 247 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 248         if (((head)->stqh_first = (elm)->field.stqe_next) == NULL)      \
 249                 (head)->stqh_last = &(head)->stqh_first;                \
 250 } while (0)
 251
 252
 253 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 254         if ((head)->stqh_first == (elm)) {                              \
 255                 STAILQ_REMOVE_HEAD(head, field);                        \
 256         }                                                               \
 257         else {                                                          \
 258                 struct type *curelm = (head)->stqh_first;               \
 259                 while( curelm->field.stqe_next != (elm) )               \
 260                         curelm = curelm->field.stqe_next;               \
 261                 if((curelm->field.stqe_next =                           \
 262                     curelm->field.stqe_next->field.stqe_next) == NULL)  \
 263                         (head)->stqh_last = &(curelm)->field.stqe_next; \
 264         }                                                               \
 265 } while (0)
 266
 267 /*
 268  * List definitions.
 269  */
 270 #define LIST_HEAD(name, type)                                           \
 271 struct name {                                                           \
 272         struct type *lh_first;  /* first element */                     \
 273 }
 274
 275 #define LIST_HEAD_INITIALIZER(head)                                     \
 276         { NULL }
 277
 278 #define LIST_ENTRY(type)                                                \
 279 struct {                                                                \
 280         struct type *le_next;   /* next element */                      \
 281         struct type **le_prev;  /* address of previous next element */  \
 282 }
 283
 284 /*
 285  * List functions.
 286  */
 287
 288 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
 289
 290 #define LIST_FIRST(head)        ((head)->lh_first)
 291
 292 #define LIST_FOREACH(var, head, field)                                  \
 293         for((var) = (head)->lh_first; (var); (var) = (var)->field.le_next)
 294
 295 #define LIST_INIT(head) do {                                            \
 296         (head)->lh_first = NULL;                                        \
 297 } while (0)
 298
 299 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 300         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 301                 (listelm)->field.le_next->field.le_prev =               \
 302                     &(elm)->field.le_next;                              \
 303         (listelm)->field.le_next = (elm);                               \
 304         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 305 } while (0)
 306
 307 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 308         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 309         (elm)->field.le_next = (listelm);                               \
 310         *(listelm)->field.le_prev = (elm);                              \
 311         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 312 } while (0)
 313
 314 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 315         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 316                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 317         (head)->lh_first = (elm);                                       \
 318         (elm)->field.le_prev = &(head)->lh_first;                       \
 319 } while (0)
 320
 321 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 322
 323 #define LIST_REMOVE(elm, field) do {                                    \
 324         if ((elm)->field.le_next != NULL)                               \
 325                 (elm)->field.le_next->field.le_prev =                   \
 326                     (elm)->field.le_prev;                               \
 327         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 328 } while (0)
 329
 330 /*
 331  * Tail queue definitions.
 332  */
 333 #define TAILQ_HEAD(name, type)                                          \
 334 struct name {                                                           \
 335         struct type *tqh_first; /* first element */                     \
 336         struct type **tqh_last; /* addr of last next element */         \
 337 }
 338
 339 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 340         { NULL, &(head).tqh_first }
 341
 342 #define TAILQ_ENTRY(type)                                               \
 343 struct {                                                                \
 344         struct type *tqe_next;  /* next element */                      \
 345         struct type **tqe_prev; /* address of previous next element */  \
 346 }
 347
 348 /*
 349  * Tail queue functions.
 350  */
 351 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
 352
 353 #define TAILQ_FOREACH(var, head, field)                                 \
 354         for (var = TAILQ_FIRST(head); var; var = TAILQ_NEXT(var, field))
 355
 356 #define TAILQ_FOREACH_REVERSE(var, head, field, headname)                                       \
 357         for (var = TAILQ_LAST(head, headname);                 \
 358                var; var = TAILQ_PREV(var, headname, field))
 359
 360 #define TAILQ_FIRST(head) ((head)->tqh_first)
 361
 362 #define TAILQ_LAST(head, headname) \
 363         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 364
 365 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 366
 367 #define TAILQ_PREV(elm, headname, field) \
 368         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 369
 370 #define TAILQ_INIT(head) do {                                           \
 371         (head)->tqh_first = NULL;                                       \
 372         (head)->tqh_last = &(head)->tqh_first;                          \
 373 } while (0)
 374
 375 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 376         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 377                 (head)->tqh_first->field.tqe_prev =                     \
 378                     &(elm)->field.tqe_next;                             \
 379         else                                                            \
 380                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 381         (head)->tqh_first = (elm);                                      \
 382         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 383 } while (0)
 384
 385 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 386         (elm)->field.tqe_next = NULL;                                   \
 387         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 388         *(head)->tqh_last = (elm);                                      \
 389         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 390 } while (0)
 391
 392 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 393         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 394                 (elm)->field.tqe_next->field.tqe_prev =                 \
 395                     &(elm)->field.tqe_next;                             \
 396         else                                                            \
 397                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 398         (listelm)->field.tqe_next = (elm);                              \
 399         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 400 } while (0)
 401
 402 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 403         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 404         (elm)->field.tqe_next = (listelm);                              \
 405         *(listelm)->field.tqe_prev = (elm);                             \
 406         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 407 } while (0)
 408
 409 #define TAILQ_REMOVE(head, elm, field) do {                             \
 410         if (((elm)->field.tqe_next) != NULL)                            \
 411                 (elm)->field.tqe_next->field.tqe_prev =                 \
 412                     (elm)->field.tqe_prev;                              \
 413         else                                                            \
 414                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 415         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 416 } while (0)
 417
 418 /*
 419  * Circular queue definitions.
 420  */
 421 #define CIRCLEQ_HEAD(name, type)                                        \
 422 struct name {                                                           \
 423         struct type *cqh_first;         /* first element */             \
 424         struct type *cqh_last;          /* last element */              \
 425 }
 426
 427 #define CIRCLEQ_ENTRY(type)                                             \
 428 struct {                                                                \
 429         struct type *cqe_next;          /* next element */              \
 430         struct type *cqe_prev;          /* previous element */          \
 431 }
 432
 433 /*
 434  * Circular queue functions.
 435  */
 436 #define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head))
 437
 438 #define CIRCLEQ_FIRST(head) ((head)->cqh_first)
 439
 440 #define CIRCLEQ_FOREACH(var, head, field)                               \
 441         for((var) = (head)->cqh_first;                                  \
 442             (var) != (void *)(head);                                    \
 443             (var) = (var)->field.cqe_next)
 444
 445 #define CIRCLEQ_INIT(head) do {                                         \
 446         (head)->cqh_first = (void *)(head);                             \
 447         (head)->cqh_last = (void *)(head);                              \
 448 } while (0)
 449
 450 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 451         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 452         (elm)->field.cqe_prev = (listelm);                              \
 453         if ((listelm)->field.cqe_next == (void *)(head))                \
 454                 (head)->cqh_last = (elm);                               \
 455         else                                                            \
 456                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 457         (listelm)->field.cqe_next = (elm);                              \
 458 } while (0)
 459
 460 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 461         (elm)->field.cqe_next = (listelm);                              \
 462         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 463         if ((listelm)->field.cqe_prev == (void *)(head))                \
 464                 (head)->cqh_first = (elm);                              \
 465         else                                                            \
 466                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 467         (listelm)->field.cqe_prev = (elm);                              \
 468 } while (0)
 469
 470 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 471         (elm)->field.cqe_next = (head)->cqh_first;                      \
 472         (elm)->field.cqe_prev = (void *)(head);                         \
 473         if ((head)->cqh_last == (void *)(head))                         \
 474                 (head)->cqh_last = (elm);                               \
 475         else                                                            \
 476                 (head)->cqh_first->field.cqe_prev = (elm);              \
 477         (head)->cqh_first = (elm);                                      \
 478 } while (0)
 479
 480 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 481         (elm)->field.cqe_next = (void *)(head);                         \
 482         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 483         if ((head)->cqh_first == (void *)(head))                        \
 484                 (head)->cqh_first = (elm);                              \
 485         else                                                            \
 486                 (head)->cqh_last->field.cqe_next = (elm);               \
 487         (head)->cqh_last = (elm);                                       \
 488 } while (0)
 489
 490 #define CIRCLEQ_LAST(head) ((head)->cqh_last)
 491
 492 #define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 493
 494 #define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 495
 496 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 497         if ((elm)->field.cqe_next == (void *)(head))                    \
 498                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 499         else                                                            \
 500                 (elm)->field.cqe_next->field.cqe_prev =                 \
 501                     (elm)->field.cqe_prev;                              \
 502         if ((elm)->field.cqe_prev == (void *)(head))                    \
 503                 (head)->cqh_first = (elm)->field.cqe_next;              \
 504         else                                                            \
 505                 (elm)->field.cqe_prev->field.cqe_next =                 \
 506                     (elm)->field.cqe_next;                              \
 507 } while (0)
 508
 509 #ifdef KERNEL
 510
 511 #if NOTFB31
 512
 513 /*
 514  * XXX insque() and remque() are an old way of handling certain queues.
 515  * They bogusly assumes that all queue heads look alike.
 516  */
 517
 518 struct quehead {
 519         struct quehead *qh_link;
 520         struct quehead *qh_rlink;
 521 };
 522
 523 #ifdef  __GNUC__
 524
 525 static __inline void
 526 insque(void *a, void *b)
 527 {
 528         struct quehead *element = a, *head = b;
 529
 530         element->qh_link = head->qh_link;
 531         element->qh_rlink = head;
 532         head->qh_link = element;
 533         element->qh_link->qh_rlink = element;
 534 }
 535
 536 static __inline void
 537 remque(void *a)
 538 {
 539         struct quehead *element = a;
 540
 541         element->qh_link->qh_rlink = element->qh_rlink;
 542         element->qh_rlink->qh_link = element->qh_link;
 543         element->qh_rlink = 0;
 544 }
 545
 546 #else /* !__GNUC__ */
 547
 548 void    insque(void *a, void *b);
 549 void    remque(void *a);
 550
 551 #endif /* __GNUC__ */
 552
 553 #endif
 554 #endif /* KERNEL */
 555
 556 #endif /* !_SYS_QUEUE_H_ */