lib/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 /*
  37  * This file defines four types of data structures: singly-linked lists,
  38  * singly-linked tail queues, lists and tail queues.
  39  *
  40  * A singly-linked list is headed by a single forward pointer. The elements
  41  * are singly linked for minimum space and pointer manipulation overhead at
  42  * the expense of O(n) removal for arbitrary elements. New elements can be
  43  * added to the list after an existing element or at the head of the list.
  44  * Elements being removed from the head of the list should use the explicit
  45  * macro for this purpose for optimum efficiency. A singly-linked list may
  46  * only be traversed in the forward direction.  Singly-linked lists are ideal
  47  * for applications with large datasets and few or no removals or for
  48  * implementing a LIFO queue.
  49  *
  50  * A singly-linked tail queue is headed by a pair of pointers, one to the
  51  * head of the list and the other to the tail of the list. The elements are
  52  * singly linked for minimum space and pointer manipulation overhead at the
  53  * expense of O(n) removal for arbitrary elements. New elements can be added
  54  * to the list after an existing element, at the head of the list, or at the
  55  * end of the list. Elements being removed from the head of the tail queue
  56  * should use the explicit macro for this purpose for optimum efficiency.
  57  * A singly-linked tail queue may only be traversed in the forward direction.
  58  * Singly-linked tail queues are ideal for applications with large datasets
  59  * and few or no removals or for implementing a FIFO queue.
  60  *
  61  * A list is headed by a single forward pointer (or an array of forward
  62  * pointers for a hash table header). The elements are doubly linked
  63  * so that an arbitrary element can be removed without a need to
  64  * traverse the list. New elements can be added to the list before
  65  * or after an existing element or at the head of the list. A list
  66  * may only be traversed in the forward direction.
  67  *
  68  * A tail queue is headed by a pair of pointers, one to the head of the
  69  * list and the other to the tail of the list. The elements are doubly
  70  * linked so that an arbitrary element can be removed without a need to
  71  * traverse the list. New elements can be added to the list before or
  72  * after an existing element, at the head of the list, or at the end of
  73  * the list. A tail queue may be traversed in either direction.
  74  *
  75  * For details on the use of these macros, see the queue(3) manual page.
  76  *
  77  *
  78  *                              SLIST   LIST    STAILQ  TAILQ
  79  * _HEAD                        +       +       +       +
  80  * _HEAD_INITIALIZER            +       +       +       +
  81  * _ENTRY                       +       +       +       +
  82  * _INIT                        +       +       +       +
  83  * _EMPTY                       +       +       +       +
  84  * _FIRST                       +       +       +       +
  85  * _NEXT                        +       +       +       +
  86  * _PREV                        -       -       -       +
  87  * _LAST                        -       -       +       +
  88  * _FOREACH                     +       +       +       +
  89  * _FOREACH_SAFE                +       +       +       +
  90  * _FOREACH_REVERSE             -       -       -       +
  91  * _FOREACH_REVERSE_SAFE        -       -       -       +
  92  * _INSERT_HEAD                 +       +       +       +
  93  * _INSERT_BEFORE               -       +       -       +
  94  * _INSERT_AFTER                +       +       +       +
  95  * _INSERT_TAIL                 -       -       +       +
  96  * _CONCAT                      -       -       +       +
  97  * _REMOVE_AFTER                +       -       +       -
  98  * _REMOVE_HEAD                 +       -       +       -
  99  * _REMOVE                      +       +       +       +
 100  * _SWAP                        +       +       +       +
 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 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 115
 116 #define QMD_TRACE_HEAD(head) do {                                       \
 117         (head)->trace.prevline = (head)->trace.lastline;                \
 118         (head)->trace.prevfile = (head)->trace.lastfile;                \
 119         (head)->trace.lastline = __LINE__;                              \
 120         (head)->trace.lastfile = __FILE__;                              \
 121 } while (0)
 122
 123 #define QMD_TRACE_ELEM(elem) do {                                       \
 124         (elem)->trace.prevline = (elem)->trace.lastline;                \
 125         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 126         (elem)->trace.lastline = __LINE__;                              \
 127         (elem)->trace.lastfile = __FILE__;                              \
 128 } while (0)
 129
 130 #else
 131 #define QMD_TRACE_ELEM(elem)
 132 #define QMD_TRACE_HEAD(head)
 133 #define QMD_SAVELINK(name, link)
 134 #define TRACEBUF
 135 #define TRASHIT(x)
 136 #endif  /* QUEUE_MACRO_DEBUG */
 137
 138 /*
 139  * Singly-linked List declarations.
 140  */
 141 #define SLIST_HEAD(name, type)                                          \
 142 struct name {                                                           \
 143         struct type *slh_first; /* first element */                     \
 144 }
 145
 146 #define SLIST_HEAD_INITIALIZER(head)                                    \
 147         { NULL }
 148
 149 #define SLIST_ENTRY(type)                                               \
 150 struct {                                                                \
 151         struct type *sle_next;  /* next element */                      \
 152 }
 153
 154 /*
 155  * Singly-linked List functions.
 156  */
 157 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 158
 159 #define SLIST_FIRST(head)       ((head)->slh_first)
 160
 161 #define SLIST_FOREACH(var, head, field)                                 \
 162         for ((var) = SLIST_FIRST((head));                               \
 163             (var);                                                      \
 164             (var) = SLIST_NEXT((var), field))
 165
 166 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 167         for ((var) = SLIST_FIRST((head));                               \
 168             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 169             (var) = (tvar))
 170
 171 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 172         for ((varp) = &SLIST_FIRST((head));                             \
 173             ((var) = *(varp)) != NULL;                                  \
 174             (varp) = &SLIST_NEXT((var), field))
 175
 176 #define SLIST_INIT(head) do {                                           \
 177         SLIST_FIRST((head)) = NULL;                                     \
 178 } while (0)
 179
 180 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 181         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 182         SLIST_NEXT((slistelm), field) = (elm);                          \
 183 } while (0)
 184
 185 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 186         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 187         SLIST_FIRST((head)) = (elm);                                    \
 188 } while (0)
 189
 190 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 191
 192 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 193         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 194         if (SLIST_FIRST((head)) == (elm)) {                             \
 195                 SLIST_REMOVE_HEAD((head), field);                       \
 196         }                                                               \
 197         else {                                                          \
 198                 struct type *curelm = SLIST_FIRST((head));              \
 199                 while (SLIST_NEXT(curelm, field) != (elm))              \
 200                         curelm = SLIST_NEXT(curelm, field);             \
 201                 SLIST_REMOVE_AFTER(curelm, field);                      \
 202         }                                                               \
 203         TRASHIT(*oldnext);                                              \
 204 } while (0)
 205
 206 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 207         SLIST_NEXT(elm, field) =                                        \
 208             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 209 } while (0)
 210
 211 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 212         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 213 } while (0)
 214
 215 #define SLIST_SWAP(head1, head2, type) do {                             \
 216         struct type *swap_first = SLIST_FIRST(head1);                   \
 217         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
 218         SLIST_FIRST(head2) = swap_first;                                \
 219 } while (0)
 220
 221 /*
 222  * Singly-linked Tail queue declarations.
 223  */
 224 #define STAILQ_HEAD(name, type)                                         \
 225 struct name {                                                           \
 226         struct type *stqh_first;/* first element */                     \
 227         struct type **stqh_last;/* addr of last next element */         \
 228 }
 229
 230 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 231         { NULL, &(head).stqh_first }
 232
 233 #define STAILQ_ENTRY(type)                                              \
 234 struct {                                                                \
 235         struct type *stqe_next; /* next element */                      \
 236 }
 237
 238 /*
 239  * Singly-linked Tail queue functions.
 240  */
 241 #define STAILQ_CONCAT(head1, head2) do {                                \
 242         if (!STAILQ_EMPTY((head2))) {                                   \
 243                 *(head1)->stqh_last = (head2)->stqh_first;              \
 244                 (head1)->stqh_last = (head2)->stqh_last;                \
 245                 STAILQ_INIT((head2));                                   \
 246         }                                                               \
 247 } while (0)
 248
 249 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 250
 251 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 252
 253 #define STAILQ_FOREACH(var, head, field)                                \
 254         for((var) = STAILQ_FIRST((head));                               \
 255            (var);                                                       \
 256            (var) = STAILQ_NEXT((var), field))
 257
 258
 259 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 260         for ((var) = STAILQ_FIRST((head));                              \
 261             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 262             (var) = (tvar))
 263
 264 #define STAILQ_INIT(head) do {                                          \
 265         STAILQ_FIRST((head)) = NULL;                                    \
 266         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 267 } while (0)
 268
 269 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 270         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 271                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 272         STAILQ_NEXT((tqelm), field) = (elm);                            \
 273 } while (0)
 274
 275 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 276         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 277                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 278         STAILQ_FIRST((head)) = (elm);                                   \
 279 } while (0)
 280
 281 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 282         STAILQ_NEXT((elm), field) = NULL;                               \
 283         *(head)->stqh_last = (elm);                                     \
 284         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 285 } while (0)
 286
 287 #define STAILQ_LAST(head, type, field)                                  \
 288         (STAILQ_EMPTY((head)) ?                                         \
 289                 NULL :                                                  \
 290                 ((struct type *)(void *)                                \
 291                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 292
 293 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 294
 295 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 296         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 297         if (STAILQ_FIRST((head)) == (elm)) {                            \
 298                 STAILQ_REMOVE_HEAD((head), field);                      \
 299         }                                                               \
 300         else {                                                          \
 301                 struct type *curelm = STAILQ_FIRST((head));             \
 302                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 303                         curelm = STAILQ_NEXT(curelm, field);            \
 304                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 305         }                                                               \
 306         TRASHIT(*oldnext);                                              \
 307 } while (0)
 308
 309 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 310         if ((STAILQ_NEXT(elm, field) =                                  \
 311              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 312                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 313 } while (0)
 314
 315 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 316         if ((STAILQ_FIRST((head)) =                                     \
 317              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 318                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 319 } while (0)
 320
 321 #define STAILQ_SWAP(head1, head2, type) do {                            \
 322         struct type *swap_first = STAILQ_FIRST(head1);                  \
 323         struct type **swap_last = (head1)->stqh_last;                   \
 324         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 325         (head1)->stqh_last = (head2)->stqh_last;                        \
 326         STAILQ_FIRST(head2) = swap_first;                               \
 327         (head2)->stqh_last = swap_last;                                 \
 328         if (STAILQ_EMPTY(head1))                                        \
 329                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 330         if (STAILQ_EMPTY(head2))                                        \
 331                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 332 } while (0)
 333
 334
 335 /*
 336  * List declarations.
 337  */
 338 #define LIST_HEAD(name, type)                                           \
 339 struct name {                                                           \
 340         struct type *lh_first;  /* first element */                     \
 341 }
 342
 343 #define LIST_HEAD_INITIALIZER(head)                                     \
 344         { NULL }
 345
 346 #define LIST_ENTRY(type)                                                \
 347 struct {                                                                \
 348         struct type *le_next;   /* next element */                      \
 349         struct type **le_prev;  /* address of previous next element */  \
 350 }
 351
 352 /*
 353  * List functions.
 354  */
 355
 356 #if (defined(_KERNEL) && defined(INVARIANTS))
 357 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 358         if (LIST_FIRST((head)) != NULL &&                               \
 359             LIST_FIRST((head))->field.le_prev !=                        \
 360              &LIST_FIRST((head)))                                       \
 361                 panic("Bad list head %p first->prev != head", (head));  \
 362 } while (0)
 363
 364 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 365         if (LIST_NEXT((elm), field) != NULL &&                          \
 366             LIST_NEXT((elm), field)->field.le_prev !=                   \
 367              &((elm)->field.le_next))                                   \
 368                 panic("Bad link elm %p next->prev != elm", (elm));      \
 369 } while (0)
 370
 371 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 372         if (*(elm)->field.le_prev != (elm))                             \
 373                 panic("Bad link elm %p prev->next != elm", (elm));      \
 374 } while (0)
 375 #else
 376 #define QMD_LIST_CHECK_HEAD(head, field)
 377 #define QMD_LIST_CHECK_NEXT(elm, field)
 378 #define QMD_LIST_CHECK_PREV(elm, field)
 379 #endif /* (_KERNEL && INVARIANTS) */
 380
 381 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 382
 383 #define LIST_FIRST(head)        ((head)->lh_first)
 384
 385 #define LIST_FOREACH(var, head, field)                                  \
 386         for ((var) = LIST_FIRST((head));                                \
 387             (var);                                                      \
 388             (var) = LIST_NEXT((var), field))
 389
 390 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 391         for ((var) = LIST_FIRST((head));                                \
 392             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 393             (var) = (tvar))
 394
 395 #define LIST_INIT(head) do {                                            \
 396         LIST_FIRST((head)) = NULL;                                      \
 397 } while (0)
 398
 399 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 400         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 401         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 402                 LIST_NEXT((listelm), field)->field.le_prev =            \
 403                     &LIST_NEXT((elm), field);                           \
 404         LIST_NEXT((listelm), field) = (elm);                            \
 405         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 406 } while (0)
 407
 408 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 409         QMD_LIST_CHECK_PREV(listelm, field);                            \
 410         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 411         LIST_NEXT((elm), field) = (listelm);                            \
 412         *(listelm)->field.le_prev = (elm);                              \
 413         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 414 } while (0)
 415
 416 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 417         QMD_LIST_CHECK_HEAD((head), field);                             \
 418         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 419                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 420         LIST_FIRST((head)) = (elm);                                     \
 421         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 422 } while (0)
 423
 424 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 425
 426 #define LIST_REMOVE(elm, field) do {                                    \
 427         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 428         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 429         QMD_LIST_CHECK_NEXT(elm, field);                                \
 430         QMD_LIST_CHECK_PREV(elm, field);                                \
 431         if (LIST_NEXT((elm), field) != NULL)                            \
 432                 LIST_NEXT((elm), field)->field.le_prev =                \
 433                     (elm)->field.le_prev;                               \
 434         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 435         TRASHIT(*oldnext);                                              \
 436         TRASHIT(*oldprev);                                              \
 437 } while (0)
 438
 439 #define LIST_SWAP(head1, head2, type, field) do {                       \
 440         struct type *swap_tmp = LIST_FIRST((head1));                    \
 441         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 442         LIST_FIRST((head2)) = swap_tmp;                                 \
 443         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 444                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 445         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 446                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 447 } while (0)
 448
 449 /*
 450  * Tail queue declarations.
 451  */
 452 #define TAILQ_HEAD(name, type)                                          \
 453 struct name {                                                           \
 454         struct type *tqh_first; /* first element */                     \
 455         struct type **tqh_last; /* addr of last next element */         \
 456         TRACEBUF                                                        \
 457 }
 458
 459 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 460         { NULL, &(head).tqh_first }
 461
 462 #define TAILQ_ENTRY(type)                                               \
 463 struct {                                                                \
 464         struct type *tqe_next;  /* next element */                      \
 465         struct type **tqe_prev; /* address of previous next element */  \
 466         TRACEBUF                                                        \
 467 }
 468
 469 /*
 470  * Tail queue functions.
 471  */
 472 #if (defined(_KERNEL) && defined(INVARIANTS))
 473 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 474         if (!TAILQ_EMPTY(head) &&                                       \
 475             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 476              &TAILQ_FIRST((head)))                                      \
 477                 panic("Bad tailq head %p first->prev != head", (head)); \
 478 } while (0)
 479
 480 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 481         if (*(head)->tqh_last != NULL)                                  \
 482                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 483 } while (0)
 484
 485 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 486         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 487             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 488              &((elm)->field.tqe_next))                                  \
 489                 panic("Bad link elm %p next->prev != elm", (elm));      \
 490 } while (0)
 491
 492 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 493         if (*(elm)->field.tqe_prev != (elm))                            \
 494                 panic("Bad link elm %p prev->next != elm", (elm));      \
 495 } while (0)
 496 #else
 497 #define QMD_TAILQ_CHECK_HEAD(head, field)
 498 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 499 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 500 #define QMD_TAILQ_CHECK_PREV(elm, field)
 501 #endif /* (_KERNEL && INVARIANTS) */
 502
 503 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 504         if (!TAILQ_EMPTY(head2)) {                                      \
 505                 *(head1)->tqh_last = (head2)->tqh_first;                \
 506                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 507                 (head1)->tqh_last = (head2)->tqh_last;                  \
 508                 TAILQ_INIT((head2));                                    \
 509                 QMD_TRACE_HEAD(head1);                                  \
 510                 QMD_TRACE_HEAD(head2);                                  \
 511         }                                                               \
 512 } while (0)
 513
 514 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 515
 516 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 517
 518 #define TAILQ_FOREACH(var, head, field)                                 \
 519         for ((var) = TAILQ_FIRST((head));                               \
 520             (var);                                                      \
 521             (var) = TAILQ_NEXT((var), field))
 522
 523 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 524         for ((var) = TAILQ_FIRST((head));                               \
 525             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 526             (var) = (tvar))
 527
 528 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 529         for ((var) = TAILQ_LAST((head), headname);                      \
 530             (var);                                                      \
 531             (var) = TAILQ_PREV((var), headname, field))
 532
 533 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 534         for ((var) = TAILQ_LAST((head), headname);                      \
 535             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 536             (var) = (tvar))
 537
 538 #define TAILQ_INIT(head) do {                                           \
 539         TAILQ_FIRST((head)) = NULL;                                     \
 540         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 541         QMD_TRACE_HEAD(head);                                           \
 542 } while (0)
 543
 544 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 545         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 546         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 547                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 548                     &TAILQ_NEXT((elm), field);                          \
 549         else {                                                          \
 550                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 551                 QMD_TRACE_HEAD(head);                                   \
 552         }                                                               \
 553         TAILQ_NEXT((listelm), field) = (elm);                           \
 554         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 555         QMD_TRACE_ELEM(&(elm)->field);                                  \
 556         QMD_TRACE_ELEM(&listelm->field);                                \
 557 } while (0)
 558
 559 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 560         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 561         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 562         TAILQ_NEXT((elm), field) = (listelm);                           \
 563         *(listelm)->field.tqe_prev = (elm);                             \
 564         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 565         QMD_TRACE_ELEM(&(elm)->field);                                  \
 566         QMD_TRACE_ELEM(&listelm->field);                                \
 567 } while (0)
 568
 569 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 570         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 571         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 572                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 573                     &TAILQ_NEXT((elm), field);                          \
 574         else                                                            \
 575                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 576         TAILQ_FIRST((head)) = (elm);                                    \
 577         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 578         QMD_TRACE_HEAD(head);                                           \
 579         QMD_TRACE_ELEM(&(elm)->field);                                  \
 580 } while (0)
 581
 582 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 583         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 584         TAILQ_NEXT((elm), field) = NULL;                                \
 585         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 586         *(head)->tqh_last = (elm);                                      \
 587         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 588         QMD_TRACE_HEAD(head);                                           \
 589         QMD_TRACE_ELEM(&(elm)->field);                                  \
 590 } while (0)
 591
 592 #define TAILQ_LAST(head, headname)                                      \
 593         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 594
 595 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 596
 597 #define TAILQ_PREV(elm, headname, field)                                \
 598         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 599
 600 #define TAILQ_REMOVE(head, elm, field) do {                             \
 601         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 602         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 603         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 604         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 605         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 606                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 607                     (elm)->field.tqe_prev;                              \
 608         else {                                                          \
 609                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 610                 QMD_TRACE_HEAD(head);                                   \
 611         }                                                               \
 612         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 613         TRASHIT(*oldnext);                                              \
 614         TRASHIT(*oldprev);                                              \
 615         QMD_TRACE_ELEM(&(elm)->field);                                  \
 616 } while (0)
 617
 618 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 619         struct type *swap_first = (head1)->tqh_first;                   \
 620         struct type **swap_last = (head1)->tqh_last;                    \
 621         (head1)->tqh_first = (head2)->tqh_first;                        \
 622         (head1)->tqh_last = (head2)->tqh_last;                          \
 623         (head2)->tqh_first = swap_first;                                \
 624         (head2)->tqh_last = swap_last;                                  \
 625         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 626                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 627         else                                                            \
 628                 (head1)->tqh_last = &(head1)->tqh_first;                \
 629         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 630                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 631         else                                                            \
 632                 (head2)->tqh_last = &(head2)->tqh_first;                \
 633 } while (0)
 634
 635 #endif /* !_SYS_QUEUE_H_ */