bsd/sys/queue.h

   1 /*
   2  * Copyright (c) 2006 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_OSREFERENCE_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
  10  * License may not be used to create, or enable the creation or
  11  * redistribution of, unlawful or unlicensed copies of an Apple operating
  12  * system, or to circumvent, violate, or enable the circumvention or
  13  * violation of, any terms of an Apple operating system software license
  14  * agreement.
  15  *
  16  * Please obtain a copy of the License at
  17  * http://www.opensource.apple.com/apsl/ and read it before using this
  18  * file.
  19  *
  20  * The Original Code and all software distributed under the License are
  21  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  22  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  23  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  25  * Please see the License for the specific language governing rights and
  26  * limitations under the License.
  27  *
  28  * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
  29  */
  30 /*
  31  * Copyright (c) 1991, 1993
  32  *      The Regents of the University of California.  All rights reserved.
  33  *
  34  * Redistribution and use in source and binary forms, with or without
  35  * modification, are permitted provided that the following conditions
  36  * are met:
  37  * 1. Redistributions of source code must retain the above copyright
  38  *    notice, this list of conditions and the following disclaimer.
  39  * 2. Redistributions in binary form must reproduce the above copyright
  40  *    notice, this list of conditions and the following disclaimer in the
  41  *    documentation and/or other materials provided with the distribution.
  42  * 3. All advertising materials mentioning features or use of this software
  43  *    must display the following acknowledgement:
  44  *      This product includes software developed by the University of
  45  *      California, Berkeley and its contributors.
  46  * 4. Neither the name of the University nor the names of its contributors
  47  *    may be used to endorse or promote products derived from this software
  48  *    without specific prior written permission.
  49  *
  50  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  51  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  53  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  54  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  55  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  56  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  57  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  58  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  59  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  60  * SUCH DAMAGE.
  61  *
  62  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  63  */
  64
  65 #ifndef _SYS_QUEUE_H_
  66 #define _SYS_QUEUE_H_
  67
  68 /*
  69  * This file defines five types of data structures: singly-linked lists,
  70  * slingly-linked tail queues, lists, tail queues, and circular queues.
  71  *
  72  * A singly-linked list is headed by a single forward pointer. The elements
  73  * are singly linked for minimum space and pointer manipulation overhead at
  74  * the expense of O(n) removal for arbitrary elements. New elements can be
  75  * added to the list after an existing element or at the head of the list.
  76  * Elements being removed from the head of the list should use the explicit
  77  * macro for this purpose for optimum efficiency. A singly-linked list may
  78  * only be traversed in the forward direction.  Singly-linked lists are ideal
  79  * for applications with large datasets and few or no removals or for
  80  * implementing a LIFO queue.
  81  *
  82  * A singly-linked tail queue is headed by a pair of pointers, one to the
  83  * head of the list and the other to the tail of the list. The elements are
  84  * singly linked for minimum space and pointer manipulation overhead at the
  85  * expense of O(n) removal for arbitrary elements. New elements can be added
  86  * to the list after an existing element, at the head of the list, or at the
  87  * end of the list. Elements being removed from the head of the tail queue
  88  * should use the explicit macro for this purpose for optimum efficiency.
  89  * A singly-linked tail queue may only be traversed in the forward direction.
  90  * Singly-linked tail queues are ideal for applications with large datasets
  91  * and few or no removals or for implementing a FIFO queue.
  92  *
  93  * A list is headed by a single forward pointer (or an array of forward
  94  * pointers for a hash table header). The elements are doubly linked
  95  * so that an arbitrary element can be removed without a need to
  96  * traverse the list. New elements can be added to the list before
  97  * or after an existing element or at the head of the list. A list
  98  * may only be traversed in the forward direction.
  99  *
 100  * A tail queue is headed by a pair of pointers, one to the head of the
 101  * list and the other to the tail of the list. The elements are doubly
 102  * linked so that an arbitrary element can be removed without a need to
 103  * traverse the list. New elements can be added to the list before or
 104  * after an existing element, at the head of the list, or at the end of
 105  * the list. A tail queue may only be traversed in the forward direction.
 106  *
 107  * A circle queue is headed by a pair of pointers, one to the head of the
 108  * list and the other to the tail of the list. The elements are doubly
 109  * linked so that an arbitrary element can be removed without a need to
 110  * traverse the list. New elements can be added to the list before or after
 111  * an existing element, at the head of the list, or at the end of the list.
 112  * A circle queue may be traversed in either direction, but has a more
 113  * complex end of list detection.
 114  *
 115  * For details on the use of these macros, see the queue(3) manual page.
 116  *
 117  *
 118  *                      SLIST   LIST    STAILQ  TAILQ   CIRCLEQ
 119  * _HEAD                +       +       +       +       +
 120  * _ENTRY               +       +       +       +       +
 121  * _INIT                +       +       +       +       +
 122  * _EMPTY               +       +       +       +       +
 123  * _FIRST               +       +       +       +       +
 124  * _NEXT                +       +       +       +       +
 125  * _PREV                -       -       -       +       +
 126  * _LAST                -       -       +       +       +
 127  * _FOREACH             +       +       -       +       +
 128  * _INSERT_HEAD         +       +       +       +       +
 129  * _INSERT_BEFORE       -       +       -       +       +
 130  * _INSERT_AFTER        +       +       +       +       +
 131  * _INSERT_TAIL         -       -       +       +       +
 132  * _REMOVE_HEAD         +       -       +       -       -
 133  * _REMOVE              +       +       +       +       +
 134  *
 135  */
 136
 137 /*
 138  * Singly-linked List definitions.
 139  */
 140 #define SLIST_HEAD(name, type)                                          \
 141 struct name {                                                           \
 142         struct type *slh_first; /* first element */                     \
 143 }
 144
 145 #define SLIST_ENTRY(type)                                               \
 146 struct {                                                                \
 147         struct type *sle_next;  /* next element */                      \
 148 }
 149
 150 /*
 151  * Singly-linked List functions.
 152  */
 153 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 154
 155 #define SLIST_FIRST(head)       ((head)->slh_first)
 156
 157 #define SLIST_FOREACH(var, head, field)                                 \
 158         for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
 159
 160 #define SLIST_INIT(head) {                                              \
 161         (head)->slh_first = NULL;                                       \
 162 }
 163
 164 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 165         (elm)->field.sle_next = (slistelm)->field.sle_next;             \
 166         (slistelm)->field.sle_next = (elm);                             \
 167 } while (0)
 168
 169 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 170         (elm)->field.sle_next = (head)->slh_first;                      \
 171         (head)->slh_first = (elm);                                      \
 172 } while (0)
 173
 174 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 175
 176 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 177         (head)->slh_first = (head)->slh_first->field.sle_next;          \
 178 } while (0)
 179
 180 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 181         if ((head)->slh_first == (elm)) {                               \
 182                 SLIST_REMOVE_HEAD((head), field);                       \
 183         }                                                               \
 184         else {                                                          \
 185                 struct type *curelm = (head)->slh_first;                \
 186                 while( curelm->field.sle_next != (elm) )                \
 187                         curelm = curelm->field.sle_next;                \
 188                 curelm->field.sle_next =                                \
 189                     curelm->field.sle_next->field.sle_next;             \
 190         }                                                               \
 191 } while (0)
 192
 193 /*
 194  * Singly-linked Tail queue definitions.
 195  */
 196 #define STAILQ_HEAD(name, type)                                         \
 197 struct name {                                                           \
 198         struct type *stqh_first;/* first element */                     \
 199         struct type **stqh_last;/* addr of last next element */         \
 200 }
 201
 202 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 203         { NULL, &(head).stqh_first }
 204
 205 #define STAILQ_ENTRY(type)                                              \
 206 struct {                                                                \
 207         struct type *stqe_next; /* next element */                      \
 208 }
 209
 210 /*
 211  * Singly-linked Tail queue functions.
 212  */
 213 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
 214
 215 #define STAILQ_INIT(head) do {                                          \
 216         (head)->stqh_first = NULL;                                      \
 217         (head)->stqh_last = &(head)->stqh_first;                        \
 218 } while (0)
 219
 220 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 221 #define STAILQ_LAST(head)       (*(head)->stqh_last)
 222
 223 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 224         if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)      \
 225                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 226         (head)->stqh_first = (elm);                                     \
 227 } while (0)
 228
 229 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 230         (elm)->field.stqe_next = NULL;                                  \
 231         *(head)->stqh_last = (elm);                                     \
 232         (head)->stqh_last = &(elm)->field.stqe_next;                    \
 233 } while (0)
 234
 235 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 236         if (((elm)->field.stqe_next = (tqelm)->field.stqe_next) == NULL)\
 237                 (head)->stqh_last = &(elm)->field.stqe_next;            \
 238         (tqelm)->field.stqe_next = (elm);                               \
 239 } while (0)
 240
 241 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 242
 243 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 244         if (((head)->stqh_first =                                       \
 245              (head)->stqh_first->field.stqe_next) == NULL)              \
 246                 (head)->stqh_last = &(head)->stqh_first;                \
 247 } while (0)
 248
 249 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 250         if (((head)->stqh_first = (elm)->field.stqe_next) == NULL)      \
 251                 (head)->stqh_last = &(head)->stqh_first;                \
 252 } while (0)
 253
 254
 255 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 256         if ((head)->stqh_first == (elm)) {                              \
 257                 STAILQ_REMOVE_HEAD(head, field);                        \
 258         }                                                               \
 259         else {                                                          \
 260                 struct type *curelm = (head)->stqh_first;               \
 261                 while( curelm->field.stqe_next != (elm) )               \
 262                         curelm = curelm->field.stqe_next;               \
 263                 if((curelm->field.stqe_next =                           \
 264                     curelm->field.stqe_next->field.stqe_next) == NULL)  \
 265                         (head)->stqh_last = &(curelm)->field.stqe_next; \
 266         }                                                               \
 267 } while (0)
 268
 269 /*
 270  * List definitions.
 271  */
 272 #define LIST_HEAD(name, type)                                           \
 273 struct name {                                                           \
 274         struct type *lh_first;  /* first element */                     \
 275 }
 276
 277 #define LIST_HEAD_INITIALIZER(head)                                     \
 278         { NULL }
 279
 280 #define LIST_ENTRY(type)                                                \
 281 struct {                                                                \
 282         struct type *le_next;   /* next element */                      \
 283         struct type **le_prev;  /* address of previous next element */  \
 284 }
 285
 286 /*
 287  * List functions.
 288  */
 289
 290 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
 291
 292 #define LIST_FIRST(head)        ((head)->lh_first)
 293
 294 #define LIST_FOREACH(var, head, field)                                  \
 295         for((var) = (head)->lh_first; (var); (var) = (var)->field.le_next)
 296
 297 #define LIST_INIT(head) do {                                            \
 298         (head)->lh_first = NULL;                                        \
 299 } while (0)
 300
 301 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 302         if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)  \
 303                 (listelm)->field.le_next->field.le_prev =               \
 304                     &(elm)->field.le_next;                              \
 305         (listelm)->field.le_next = (elm);                               \
 306         (elm)->field.le_prev = &(listelm)->field.le_next;               \
 307 } while (0)
 308
 309 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 310         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 311         (elm)->field.le_next = (listelm);                               \
 312         *(listelm)->field.le_prev = (elm);                              \
 313         (listelm)->field.le_prev = &(elm)->field.le_next;               \
 314 } while (0)
 315
 316 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 317         if (((elm)->field.le_next = (head)->lh_first) != NULL)          \
 318                 (head)->lh_first->field.le_prev = &(elm)->field.le_next;\
 319         (head)->lh_first = (elm);                                       \
 320         (elm)->field.le_prev = &(head)->lh_first;                       \
 321 } while (0)
 322
 323 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 324
 325 #define LIST_REMOVE(elm, field) do {                                    \
 326         if ((elm)->field.le_next != NULL)                               \
 327                 (elm)->field.le_next->field.le_prev =                   \
 328                     (elm)->field.le_prev;                               \
 329         *(elm)->field.le_prev = (elm)->field.le_next;                   \
 330 } while (0)
 331
 332 /*
 333  * Tail queue definitions.
 334  */
 335 #define TAILQ_HEAD(name, type)                                          \
 336 struct name {                                                           \
 337         struct type *tqh_first; /* first element */                     \
 338         struct type **tqh_last; /* addr of last next element */         \
 339 }
 340
 341 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 342         { NULL, &(head).tqh_first }
 343
 344 #define TAILQ_ENTRY(type)                                               \
 345 struct {                                                                \
 346         struct type *tqe_next;  /* next element */                      \
 347         struct type **tqe_prev; /* address of previous next element */  \
 348 }
 349
 350 /*
 351  * Tail queue functions.
 352  */
 353 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
 354
 355 #define TAILQ_FOREACH(var, head, field)                                 \
 356         for (var = TAILQ_FIRST(head); var; var = TAILQ_NEXT(var, field))
 357
 358 #define TAILQ_FOREACH_REVERSE(var, head, field, headname)                                       \
 359         for (var = TAILQ_LAST(head, headname);                 \
 360                var; var = TAILQ_PREV(var, headname, field))
 361
 362 #define TAILQ_FIRST(head) ((head)->tqh_first)
 363
 364 #define TAILQ_LAST(head, headname) \
 365         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 366
 367 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 368
 369 #define TAILQ_PREV(elm, headname, field) \
 370         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 371
 372 #define TAILQ_INIT(head) do {                                           \
 373         (head)->tqh_first = NULL;                                       \
 374         (head)->tqh_last = &(head)->tqh_first;                          \
 375 } while (0)
 376
 377 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 378         if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)        \
 379                 (head)->tqh_first->field.tqe_prev =                     \
 380                     &(elm)->field.tqe_next;                             \
 381         else                                                            \
 382                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 383         (head)->tqh_first = (elm);                                      \
 384         (elm)->field.tqe_prev = &(head)->tqh_first;                     \
 385 } while (0)
 386
 387 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 388         (elm)->field.tqe_next = NULL;                                   \
 389         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 390         *(head)->tqh_last = (elm);                                      \
 391         (head)->tqh_last = &(elm)->field.tqe_next;                      \
 392 } while (0)
 393
 394 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 395         if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != NULL)\
 396                 (elm)->field.tqe_next->field.tqe_prev =                 \
 397                     &(elm)->field.tqe_next;                             \
 398         else                                                            \
 399                 (head)->tqh_last = &(elm)->field.tqe_next;              \
 400         (listelm)->field.tqe_next = (elm);                              \
 401         (elm)->field.tqe_prev = &(listelm)->field.tqe_next;             \
 402 } while (0)
 403
 404 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 405         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 406         (elm)->field.tqe_next = (listelm);                              \
 407         *(listelm)->field.tqe_prev = (elm);                             \
 408         (listelm)->field.tqe_prev = &(elm)->field.tqe_next;             \
 409 } while (0)
 410
 411 #define TAILQ_REMOVE(head, elm, field) do {                             \
 412         if (((elm)->field.tqe_next) != NULL)                            \
 413                 (elm)->field.tqe_next->field.tqe_prev =                 \
 414                     (elm)->field.tqe_prev;                              \
 415         else                                                            \
 416                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 417         *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
 418 } while (0)
 419
 420 /*
 421  * Circular queue definitions.
 422  */
 423 #define CIRCLEQ_HEAD(name, type)                                        \
 424 struct name {                                                           \
 425         struct type *cqh_first;         /* first element */             \
 426         struct type *cqh_last;          /* last element */              \
 427 }
 428
 429 #define CIRCLEQ_ENTRY(type)                                             \
 430 struct {                                                                \
 431         struct type *cqe_next;          /* next element */              \
 432         struct type *cqe_prev;          /* previous element */          \
 433 }
 434
 435 /*
 436  * Circular queue functions.
 437  */
 438 #define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void *)(head))
 439
 440 #define CIRCLEQ_FIRST(head) ((head)->cqh_first)
 441
 442 #define CIRCLEQ_FOREACH(var, head, field)                               \
 443         for((var) = (head)->cqh_first;                                  \
 444             (var) != (void *)(head);                                    \
 445             (var) = (var)->field.cqe_next)
 446
 447 #define CIRCLEQ_INIT(head) do {                                         \
 448         (head)->cqh_first = (void *)(head);                             \
 449         (head)->cqh_last = (void *)(head);                              \
 450 } while (0)
 451
 452 #define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {            \
 453         (elm)->field.cqe_next = (listelm)->field.cqe_next;              \
 454         (elm)->field.cqe_prev = (listelm);                              \
 455         if ((listelm)->field.cqe_next == (void *)(head))                \
 456                 (head)->cqh_last = (elm);                               \
 457         else                                                            \
 458                 (listelm)->field.cqe_next->field.cqe_prev = (elm);      \
 459         (listelm)->field.cqe_next = (elm);                              \
 460 } while (0)
 461
 462 #define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {           \
 463         (elm)->field.cqe_next = (listelm);                              \
 464         (elm)->field.cqe_prev = (listelm)->field.cqe_prev;              \
 465         if ((listelm)->field.cqe_prev == (void *)(head))                \
 466                 (head)->cqh_first = (elm);                              \
 467         else                                                            \
 468                 (listelm)->field.cqe_prev->field.cqe_next = (elm);      \
 469         (listelm)->field.cqe_prev = (elm);                              \
 470 } while (0)
 471
 472 #define CIRCLEQ_INSERT_HEAD(head, elm, field) do {                      \
 473         (elm)->field.cqe_next = (head)->cqh_first;                      \
 474         (elm)->field.cqe_prev = (void *)(head);                         \
 475         if ((head)->cqh_last == (void *)(head))                         \
 476                 (head)->cqh_last = (elm);                               \
 477         else                                                            \
 478                 (head)->cqh_first->field.cqe_prev = (elm);              \
 479         (head)->cqh_first = (elm);                                      \
 480 } while (0)
 481
 482 #define CIRCLEQ_INSERT_TAIL(head, elm, field) do {                      \
 483         (elm)->field.cqe_next = (void *)(head);                         \
 484         (elm)->field.cqe_prev = (head)->cqh_last;                       \
 485         if ((head)->cqh_first == (void *)(head))                        \
 486                 (head)->cqh_first = (elm);                              \
 487         else                                                            \
 488                 (head)->cqh_last->field.cqe_next = (elm);               \
 489         (head)->cqh_last = (elm);                                       \
 490 } while (0)
 491
 492 #define CIRCLEQ_LAST(head) ((head)->cqh_last)
 493
 494 #define CIRCLEQ_NEXT(elm,field) ((elm)->field.cqe_next)
 495
 496 #define CIRCLEQ_PREV(elm,field) ((elm)->field.cqe_prev)
 497
 498 #define CIRCLEQ_REMOVE(head, elm, field) do {                           \
 499         if ((elm)->field.cqe_next == (void *)(head))                    \
 500                 (head)->cqh_last = (elm)->field.cqe_prev;               \
 501         else                                                            \
 502                 (elm)->field.cqe_next->field.cqe_prev =                 \
 503                     (elm)->field.cqe_prev;                              \
 504         if ((elm)->field.cqe_prev == (void *)(head))                    \
 505                 (head)->cqh_first = (elm)->field.cqe_next;              \
 506         else                                                            \
 507                 (elm)->field.cqe_prev->field.cqe_next =                 \
 508                     (elm)->field.cqe_next;                              \
 509 } while (0)
 510
 511 #ifdef KERNEL
 512
 513 #if NOTFB31
 514
 515 /*
 516  * XXX insque() and remque() are an old way of handling certain queues.
 517  * They bogusly assumes that all queue heads look alike.
 518  */
 519
 520 struct quehead {
 521         struct quehead *qh_link;
 522         struct quehead *qh_rlink;
 523 };
 524
 525 #ifdef  __GNUC__
 526
 527 static __inline void
 528 insque(void *a, void *b)
 529 {
 530         struct quehead *element = a, *head = b;
 531
 532         element->qh_link = head->qh_link;
 533         element->qh_rlink = head;
 534         head->qh_link = element;
 535         element->qh_link->qh_rlink = element;
 536 }
 537
 538 static __inline void
 539 remque(void *a)
 540 {
 541         struct quehead *element = a;
 542
 543         element->qh_link->qh_rlink = element->qh_rlink;
 544         element->qh_rlink->qh_link = element->qh_link;
 545         element->qh_rlink = 0;
 546 }
 547
 548 #else /* !__GNUC__ */
 549
 550 void    insque(void *a, void *b);
 551 void    remque(void *a);
 552
 553 #endif /* __GNUC__ */
 554
 555 #endif
 556 #endif /* KERNEL */
 557
 558 #endif /* !_SYS_QUEUE_H_ */