bsd/sys/queue.h

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