sys/sys/queue.h

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  30  * $FreeBSD$
  31  */
  32
  33 #ifndef _SYS_QUEUE_H_
  34 #define _SYS_QUEUE_H_
  35
  36 #include <sys/cdefs.h>
  37
  38 /*
  39  * This file defines four types of data structures: singly-linked lists,
  40  * singly-linked tail queues, lists and tail queues.
  41  *
  42  * A singly-linked list is headed by a single forward pointer. The elements
  43  * are singly linked for minimum space and pointer manipulation overhead at
  44  * the expense of O(n) removal for arbitrary elements. New elements can be
  45  * added to the list after an existing element or at the head of the list.
  46  * Elements being removed from the head of the list should use the explicit
  47  * macro for this purpose for optimum efficiency. A singly-linked list may
  48  * only be traversed in the forward direction.  Singly-linked lists are ideal
  49  * for applications with large datasets and few or no removals or for
  50  * implementing a LIFO queue.
  51  *
  52  * A singly-linked tail queue is headed by a pair of pointers, one to the
  53  * head of the list and the other to the tail of the list. The elements are
  54  * singly linked for minimum space and pointer manipulation overhead at the
  55  * expense of O(n) removal for arbitrary elements. New elements can be added
  56  * to the list after an existing element, at the head of the list, or at the
  57  * end of the list. Elements being removed from the head of the tail queue
  58  * should use the explicit macro for this purpose for optimum efficiency.
  59  * A singly-linked tail queue may only be traversed in the forward direction.
  60  * Singly-linked tail queues are ideal for applications with large datasets
  61  * and few or no removals or for implementing a FIFO queue.
  62  *
  63  * A list is headed by a single forward pointer (or an array of forward
  64  * pointers for a hash table header). The elements are doubly linked
  65  * so that an arbitrary element can be removed without a need to
  66  * traverse the list. New elements can be added to the list before
  67  * or after an existing element or at the head of the list. A list
  68  * may only be traversed in the forward direction.
  69  *
  70  * A tail queue is headed by a pair of pointers, one to the head of the
  71  * list and the other to the tail of the list. The elements are doubly
  72  * linked so that an arbitrary element can be removed without a need to
  73  * traverse the list. New elements can be added to the list before or
  74  * after an existing element, at the head of the list, or at the end of
  75  * the list. A tail queue may be traversed in either direction.
  76  *
  77  * For details on the use of these macros, see the queue(3) manual page.
  78  *
  79  *
  80  *                              SLIST   LIST    STAILQ  TAILQ
  81  * _HEAD                        +       +       +       +
  82  * _HEAD_INITIALIZER            +       +       +       +
  83  * _ENTRY                       +       +       +       +
  84  * _INIT                        +       +       +       +
  85  * _EMPTY                       +       +       +       +
  86  * _FIRST                       +       +       +       +
  87  * _NEXT                        +       +       +       +
  88  * _PREV                        -       -       -       +
  89  * _LAST                        -       -       +       +
  90  * _FOREACH                     +       +       +       +
  91  * _FOREACH_SAFE                +       +       +       +
  92  * _FOREACH_REVERSE             -       -       -       +
  93  * _FOREACH_REVERSE_SAFE        -       -       -       +
  94  * _INSERT_HEAD                 +       +       +       +
  95  * _INSERT_BEFORE               -       +       -       +
  96  * _INSERT_AFTER                +       +       +       +
  97  * _INSERT_TAIL                 -       -       +       +
  98  * _CONCAT                      -       -       +       +
  99  * _REMOVE_HEAD                 +       -       +       -
 100  * _REMOVE                      +       +       +       +
 101  *
 102  */
 103 #ifdef QUEUE_MACRO_DEBUG
 104 /* Store the last 2 places the queue element or head was altered */
 105 struct qm_trace {
 106         char * lastfile;
 107         int lastline;
 108         char * prevfile;
 109         int prevline;
 110 };
 111
 112 #define TRACEBUF        struct qm_trace trace;
 113 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 114
 115 #define QMD_TRACE_HEAD(head) do {                                       \
 116         (head)->trace.prevline = (head)->trace.lastline;                \
 117         (head)->trace.prevfile = (head)->trace.lastfile;                \
 118         (head)->trace.lastline = __LINE__;                              \
 119         (head)->trace.lastfile = __FILE__;                              \
 120 } while (0)
 121
 122 #define QMD_TRACE_ELEM(elem) do {                                       \
 123         (elem)->trace.prevline = (elem)->trace.lastline;                \
 124         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 125         (elem)->trace.lastline = __LINE__;                              \
 126         (elem)->trace.lastfile = __FILE__;                              \
 127 } while (0)
 128
 129 #else
 130 #define QMD_TRACE_ELEM(elem)
 131 #define QMD_TRACE_HEAD(head)
 132 #define TRACEBUF
 133 #define TRASHIT(x)
 134 #endif  /* QUEUE_MACRO_DEBUG */
 135
 136 /*
 137  * Singly-linked List declarations.
 138  */
 139 #define SLIST_HEAD(name, type)                                          \
 140 struct name {                                                           \
 141         struct type *slh_first; /* first element */                     \
 142 }
 143
 144 #define SLIST_HEAD_INITIALIZER(head)                                    \
 145         { NULL }
 146
 147 #define SLIST_ENTRY(type)                                               \
 148 struct {                                                                \
 149         struct type *sle_next;  /* next element */                      \
 150 }
 151
 152 /*
 153  * Singly-linked List functions.
 154  */
 155 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 156
 157 #define SLIST_FIRST(head)       ((head)->slh_first)
 158
 159 #define SLIST_FOREACH(var, head, field)                                 \
 160         for ((var) = SLIST_FIRST((head));                               \
 161             (var);                                                      \
 162             (var) = SLIST_NEXT((var), field))
 163
 164 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 165         for ((var) = SLIST_FIRST((head));                               \
 166             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 167             (var) = (tvar))
 168
 169 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 170         for ((varp) = &SLIST_FIRST((head));                             \
 171             ((var) = *(varp)) != NULL;                                  \
 172             (varp) = &SLIST_NEXT((var), field))
 173
 174 #define SLIST_INIT(head) do {                                           \
 175         SLIST_FIRST((head)) = NULL;                                     \
 176 } while (0)
 177
 178 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 179         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 180         SLIST_NEXT((slistelm), field) = (elm);                          \
 181 } while (0)
 182
 183 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 184         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 185         SLIST_FIRST((head)) = (elm);                                    \
 186 } while (0)
 187
 188 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 189
 190 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 191         if (SLIST_FIRST((head)) == (elm)) {                             \
 192                 SLIST_REMOVE_HEAD((head), field);                       \
 193         }                                                               \
 194         else {                                                          \
 195                 struct type *curelm = SLIST_FIRST((head));              \
 196                 while (SLIST_NEXT(curelm, field) != (elm))              \
 197                         curelm = SLIST_NEXT(curelm, field);             \
 198                 SLIST_NEXT(curelm, field) =                             \
 199                     SLIST_NEXT(SLIST_NEXT(curelm, field), field);       \
 200         }                                                               \
 201         TRASHIT((elm)->field.sle_next);                                 \
 202 } while (0)
 203
 204 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 205         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 206 } while (0)
 207
 208 /*
 209  * Singly-linked Tail queue declarations.
 210  */
 211 #define STAILQ_HEAD(name, type)                                         \
 212 struct name {                                                           \
 213         struct type *stqh_first;/* first element */                     \
 214         struct type **stqh_last;/* addr of last next element */         \
 215 }
 216
 217 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 218         { NULL, &(head).stqh_first }
 219
 220 #define STAILQ_ENTRY(type)                                              \
 221 struct {                                                                \
 222         struct type *stqe_next; /* next element */                      \
 223 }
 224
 225 /*
 226  * Singly-linked Tail queue functions.
 227  */
 228 #define STAILQ_CONCAT(head1, head2) do {                                \
 229         if (!STAILQ_EMPTY((head2))) {                                   \
 230                 *(head1)->stqh_last = (head2)->stqh_first;              \
 231                 (head1)->stqh_last = (head2)->stqh_last;                \
 232                 STAILQ_INIT((head2));                                   \
 233         }                                                               \
 234 } while (0)
 235
 236 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 237
 238 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 239
 240 #define STAILQ_FOREACH(var, head, field)                                \
 241         for((var) = STAILQ_FIRST((head));                               \
 242            (var);                                                       \
 243            (var) = STAILQ_NEXT((var), field))
 244
 245
 246 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 247         for ((var) = STAILQ_FIRST((head));                              \
 248             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 249             (var) = (tvar))
 250
 251 #define STAILQ_INIT(head) do {                                          \
 252         STAILQ_FIRST((head)) = NULL;                                    \
 253         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 254 } while (0)
 255
 256 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 257         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 258                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 259         STAILQ_NEXT((tqelm), field) = (elm);                            \
 260 } while (0)
 261
 262 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 263         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 264                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 265         STAILQ_FIRST((head)) = (elm);                                   \
 266 } while (0)
 267
 268 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 269         STAILQ_NEXT((elm), field) = NULL;                               \
 270         *(head)->stqh_last = (elm);                                     \
 271         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 272 } while (0)
 273
 274 #define STAILQ_LAST(head, type, field)                                  \
 275         (STAILQ_EMPTY((head)) ?                                         \
 276                 NULL :                                                  \
 277                 ((struct type *)(void *)                                \
 278                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 279
 280 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 281
 282 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 283         if (STAILQ_FIRST((head)) == (elm)) {                            \
 284                 STAILQ_REMOVE_HEAD((head), field);                      \
 285         }                                                               \
 286         else {                                                          \
 287                 struct type *curelm = STAILQ_FIRST((head));             \
 288                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 289                         curelm = STAILQ_NEXT(curelm, field);            \
 290                 if ((STAILQ_NEXT(curelm, field) =                       \
 291                      STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
 292                         (head)->stqh_last = &STAILQ_NEXT((curelm), field);\
 293         }                                                               \
 294         TRASHIT((elm)->field.stqe_next);                                \
 295 } while (0)
 296
 297 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 298         if ((STAILQ_FIRST((head)) =                                     \
 299              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 300                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 301 } while (0)
 302
 303 #define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field) do {                 \
 304         if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
 305                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 306 } while (0)
 307
 308 /*
 309  * List declarations.
 310  */
 311 #define LIST_HEAD(name, type)                                           \
 312 struct name {                                                           \
 313         struct type *lh_first;  /* first element */                     \
 314 }
 315
 316 #define LIST_HEAD_INITIALIZER(head)                                     \
 317         { NULL }
 318
 319 #define LIST_ENTRY(type)                                                \
 320 struct {                                                                \
 321         struct type *le_next;   /* next element */                      \
 322         struct type **le_prev;  /* address of previous next element */  \
 323 }
 324
 325 /*
 326  * List functions.
 327  */
 328
 329 #if (defined(_KERNEL) && defined(INVARIANTS))
 330 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 331         if (LIST_FIRST((head)) != NULL &&                               \
 332             LIST_FIRST((head))->field.le_prev !=                        \
 333              &LIST_FIRST((head)))                                       \
 334                 panic("Bad list head %p first->prev != head", (head));  \
 335 } while (0)
 336
 337 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 338         if (LIST_NEXT((elm), field) != NULL &&                          \
 339             LIST_NEXT((elm), field)->field.le_prev !=                   \
 340              &((elm)->field.le_next))                                   \
 341                 panic("Bad link elm %p next->prev != elm", (elm));      \
 342 } while (0)
 343
 344 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 345         if (*(elm)->field.le_prev != (elm))                             \
 346                 panic("Bad link elm %p prev->next != elm", (elm));      \
 347 } while (0)
 348 #else
 349 #define QMD_LIST_CHECK_HEAD(head, field)
 350 #define QMD_LIST_CHECK_NEXT(elm, field)
 351 #define QMD_LIST_CHECK_PREV(elm, field)
 352 #endif /* (_KERNEL && INVARIANTS) */
 353
 354 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 355
 356 #define LIST_FIRST(head)        ((head)->lh_first)
 357
 358 #define LIST_FOREACH(var, head, field)                                  \
 359         for ((var) = LIST_FIRST((head));                                \
 360             (var);                                                      \
 361             (var) = LIST_NEXT((var), field))
 362
 363 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 364         for ((var) = LIST_FIRST((head));                                \
 365             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 366             (var) = (tvar))
 367
 368 #define LIST_INIT(head) do {                                            \
 369         LIST_FIRST((head)) = NULL;                                      \
 370 } while (0)
 371
 372 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 373         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 374         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 375                 LIST_NEXT((listelm), field)->field.le_prev =            \
 376                     &LIST_NEXT((elm), field);                           \
 377         LIST_NEXT((listelm), field) = (elm);                            \
 378         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 379 } while (0)
 380
 381 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 382         QMD_LIST_CHECK_PREV(listelm, field);                            \
 383         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 384         LIST_NEXT((elm), field) = (listelm);                            \
 385         *(listelm)->field.le_prev = (elm);                              \
 386         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 387 } while (0)
 388
 389 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 390         QMD_LIST_CHECK_HEAD((head), field);                             \
 391         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 392                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 393         LIST_FIRST((head)) = (elm);                                     \
 394         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 395 } while (0)
 396
 397 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 398
 399 #define LIST_REMOVE(elm, field) do {                                    \
 400         QMD_LIST_CHECK_NEXT(elm, field);                                \
 401         QMD_LIST_CHECK_PREV(elm, field);                                \
 402         if (LIST_NEXT((elm), field) != NULL)                            \
 403                 LIST_NEXT((elm), field)->field.le_prev =                \
 404                     (elm)->field.le_prev;                               \
 405         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 406         TRASHIT((elm)->field.le_next);                                  \
 407         TRASHIT((elm)->field.le_prev);                                  \
 408 } while (0)
 409
 410 /*
 411  * Tail queue declarations.
 412  */
 413 #define TAILQ_HEAD(name, type)                                          \
 414 struct name {                                                           \
 415         struct type *tqh_first; /* first element */                     \
 416         struct type **tqh_last; /* addr of last next element */         \
 417         TRACEBUF                                                        \
 418 }
 419
 420 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 421         { NULL, &(head).tqh_first }
 422
 423 #define TAILQ_ENTRY(type)                                               \
 424 struct {                                                                \
 425         struct type *tqe_next;  /* next element */                      \
 426         struct type **tqe_prev; /* address of previous next element */  \
 427         TRACEBUF                                                        \
 428 }
 429
 430 /*
 431  * Tail queue functions.
 432  */
 433 #if (defined(_KERNEL) && defined(INVARIANTS))
 434 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 435         if (!TAILQ_EMPTY(head) &&                                       \
 436             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 437              &TAILQ_FIRST((head)))                                      \
 438                 panic("Bad tailq head %p first->prev != head", (head)); \
 439 } while (0)
 440
 441 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 442         if (*(head)->tqh_last != NULL)                                  \
 443                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 444 } while (0)
 445
 446 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 447         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 448             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 449              &((elm)->field.tqe_next))                                  \
 450                 panic("Bad link elm %p next->prev != elm", (elm));      \
 451 } while (0)
 452
 453 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 454         if (*(elm)->field.tqe_prev != (elm))                            \
 455                 panic("Bad link elm %p prev->next != elm", (elm));      \
 456 } while (0)
 457 #else
 458 #define QMD_TAILQ_CHECK_HEAD(head, field)
 459 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 460 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 461 #define QMD_TAILQ_CHECK_PREV(elm, field)
 462 #endif /* (_KERNEL && INVARIANTS) */
 463
 464 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 465         if (!TAILQ_EMPTY(head2)) {                                      \
 466                 *(head1)->tqh_last = (head2)->tqh_first;                \
 467                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 468                 (head1)->tqh_last = (head2)->tqh_last;                  \
 469                 TAILQ_INIT((head2));                                    \
 470                 QMD_TRACE_HEAD(head1);                                  \
 471                 QMD_TRACE_HEAD(head2);                                  \
 472         }                                                               \
 473 } while (0)
 474
 475 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 476
 477 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 478
 479 #define TAILQ_FOREACH(var, head, field)                                 \
 480         for ((var) = TAILQ_FIRST((head));                               \
 481             (var);                                                      \
 482             (var) = TAILQ_NEXT((var), field))
 483
 484 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 485         for ((var) = TAILQ_FIRST((head));                               \
 486             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 487             (var) = (tvar))
 488
 489 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 490         for ((var) = TAILQ_LAST((head), headname);                      \
 491             (var);                                                      \
 492             (var) = TAILQ_PREV((var), headname, field))
 493
 494 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 495         for ((var) = TAILQ_LAST((head), headname);                      \
 496             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 497             (var) = (tvar))
 498
 499 #define TAILQ_INIT(head) do {                                           \
 500         TAILQ_FIRST((head)) = NULL;                                     \
 501         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 502         QMD_TRACE_HEAD(head);                                           \
 503 } while (0)
 504
 505 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 506         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 507         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 508                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 509                     &TAILQ_NEXT((elm), field);                          \
 510         else {                                                          \
 511                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 512                 QMD_TRACE_HEAD(head);                                   \
 513         }                                                               \
 514         TAILQ_NEXT((listelm), field) = (elm);                           \
 515         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 516         QMD_TRACE_ELEM(&(elm)->field);                                  \
 517         QMD_TRACE_ELEM(&listelm->field);                                \
 518 } while (0)
 519
 520 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 521         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 522         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 523         TAILQ_NEXT((elm), field) = (listelm);                           \
 524         *(listelm)->field.tqe_prev = (elm);                             \
 525         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 526         QMD_TRACE_ELEM(&(elm)->field);                                  \
 527         QMD_TRACE_ELEM(&listelm->field);                                \
 528 } while (0)
 529
 530 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 531         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 532         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 533                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 534                     &TAILQ_NEXT((elm), field);                          \
 535         else                                                            \
 536                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 537         TAILQ_FIRST((head)) = (elm);                                    \
 538         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 539         QMD_TRACE_HEAD(head);                                           \
 540         QMD_TRACE_ELEM(&(elm)->field);                                  \
 541 } while (0)
 542
 543 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 544         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 545         TAILQ_NEXT((elm), field) = NULL;                                \
 546         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 547         *(head)->tqh_last = (elm);                                      \
 548         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 549         QMD_TRACE_HEAD(head);                                           \
 550         QMD_TRACE_ELEM(&(elm)->field);                                  \
 551 } while (0)
 552
 553 #define TAILQ_LAST(head, headname)                                      \
 554         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 555
 556 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 557
 558 #define TAILQ_PREV(elm, headname, field)                                \
 559         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 560
 561 #define TAILQ_REMOVE(head, elm, field) do {                             \
 562         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 563         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 564         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 565                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 566                     (elm)->field.tqe_prev;                              \
 567         else {                                                          \
 568                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 569                 QMD_TRACE_HEAD(head);                                   \
 570         }                                                               \
 571         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 572         TRASHIT((elm)->field.tqe_next);                                 \
 573         TRASHIT((elm)->field.tqe_prev);                                 \
 574         QMD_TRACE_ELEM(&(elm)->field);                                  \
 575 } while (0)
 576
 577
 578 #ifdef _KERNEL
 579
 580 /*
 581  * XXX insque() and remque() are an old way of handling certain queues.
 582  * They bogusly assumes that all queue heads look alike.
 583  */
 584
 585 struct quehead {
 586         struct quehead *qh_link;
 587         struct quehead *qh_rlink;
 588 };
 589
 590 #ifdef __CC_SUPPORTS___INLINE
 591
 592 static __inline void
 593 insque(void *a, void *b)
 594 {
 595         struct quehead *element = (struct quehead *)a,
 596                  *head = (struct quehead *)b;
 597
 598         element->qh_link = head->qh_link;
 599         element->qh_rlink = head;
 600         head->qh_link = element;
 601         element->qh_link->qh_rlink = element;
 602 }
 603
 604 static __inline void
 605 remque(void *a)
 606 {
 607         struct quehead *element = (struct quehead *)a;
 608
 609         element->qh_link->qh_rlink = element->qh_rlink;
 610         element->qh_rlink->qh_link = element->qh_link;
 611         element->qh_rlink = 0;
 612 }
 613
 614 #else /* !__CC_SUPPORTS___INLINE */
 615
 616 void    insque(void *a, void *b);
 617 void    remque(void *a);
 618
 619 #endif /* __CC_SUPPORTS___INLINE */
 620
 621 #endif /* _KERNEL */
 622
 623 #endif /* !_SYS_QUEUE_H_ */