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_AFTER                +       -       +       -
 100  * _REMOVE_HEAD                 +       -       +       -
 101  * _REMOVE                      +       +       +       +
 102  *
 103  */
 104 #ifdef QUEUE_MACRO_DEBUG
 105 /* Store the last 2 places the queue element or head was altered */
 106 struct qm_trace {
 107         char * lastfile;
 108         int lastline;
 109         char * prevfile;
 110         int prevline;
 111 };
 112
 113 #define TRACEBUF        struct qm_trace trace;
 114 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 115 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 116
 117 #define QMD_TRACE_HEAD(head) do {                                       \
 118         (head)->trace.prevline = (head)->trace.lastline;                \
 119         (head)->trace.prevfile = (head)->trace.lastfile;                \
 120         (head)->trace.lastline = __LINE__;                              \
 121         (head)->trace.lastfile = __FILE__;                              \
 122 } while (0)
 123
 124 #define QMD_TRACE_ELEM(elem) do {                                       \
 125         (elem)->trace.prevline = (elem)->trace.lastline;                \
 126         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 127         (elem)->trace.lastline = __LINE__;                              \
 128         (elem)->trace.lastfile = __FILE__;                              \
 129 } while (0)
 130
 131 #else
 132 #define QMD_TRACE_ELEM(elem)
 133 #define QMD_TRACE_HEAD(head)
 134 #define QMD_SAVELINK(name, link)
 135 #define TRACEBUF
 136 #define TRASHIT(x)
 137 #endif  /* QUEUE_MACRO_DEBUG */
 138
 139 /*
 140  * Singly-linked List declarations.
 141  */
 142 #define SLIST_HEAD(name, type)                                          \
 143 struct name {                                                           \
 144         struct type *slh_first; /* first element */                     \
 145 }
 146
 147 #define SLIST_HEAD_INITIALIZER(head)                                    \
 148         { NULL }
 149
 150 #define SLIST_ENTRY(type)                                               \
 151 struct {                                                                \
 152         struct type *sle_next;  /* next element */                      \
 153 }
 154
 155 /*
 156  * Singly-linked List functions.
 157  */
 158 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 159
 160 #define SLIST_FIRST(head)       ((head)->slh_first)
 161
 162 #define SLIST_FOREACH(var, head, field)                                 \
 163         for ((var) = SLIST_FIRST((head));                               \
 164             (var);                                                      \
 165             (var) = SLIST_NEXT((var), field))
 166
 167 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 168         for ((var) = SLIST_FIRST((head));                               \
 169             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 170             (var) = (tvar))
 171
 172 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 173         for ((varp) = &SLIST_FIRST((head));                             \
 174             ((var) = *(varp)) != NULL;                                  \
 175             (varp) = &SLIST_NEXT((var), field))
 176
 177 #define SLIST_INIT(head) do {                                           \
 178         SLIST_FIRST((head)) = NULL;                                     \
 179 } while (0)
 180
 181 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 182         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 183         SLIST_NEXT((slistelm), field) = (elm);                          \
 184 } while (0)
 185
 186 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 187         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 188         SLIST_FIRST((head)) = (elm);                                    \
 189 } while (0)
 190
 191 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 192
 193 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 194         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 195         if (SLIST_FIRST((head)) == (elm)) {                             \
 196                 SLIST_REMOVE_HEAD((head), field);                       \
 197         }                                                               \
 198         else {                                                          \
 199                 struct type *curelm = SLIST_FIRST((head));              \
 200                 while (SLIST_NEXT(curelm, field) != (elm))              \
 201                         curelm = SLIST_NEXT(curelm, field);             \
 202                 SLIST_REMOVE_AFTER(curelm, field);                      \
 203         }                                                               \
 204         TRASHIT(*oldnext);                                              \
 205 } while (0)
 206
 207 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 208         SLIST_NEXT(elm, field) =                                        \
 209             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 210 } while (0)
 211
 212 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 213         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 214 } while (0)
 215
 216 #define SLIST_SWAP(head1, head2, type) do {                             \
 217         struct type *swap_first = SLIST_FIRST(head1);                   \
 218         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
 219         SLIST_FIRST(head2) = swap_first;                                \
 220 } while (0)
 221
 222 /*
 223  * Singly-linked Tail queue declarations.
 224  */
 225 #define STAILQ_HEAD(name, type)                                         \
 226 struct name {                                                           \
 227         struct type *stqh_first;/* first element */                     \
 228         struct type **stqh_last;/* addr of last next element */         \
 229 }
 230
 231 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 232         { NULL, &(head).stqh_first }
 233
 234 #define STAILQ_ENTRY(type)                                              \
 235 struct {                                                                \
 236         struct type *stqe_next; /* next element */                      \
 237 }
 238
 239 /*
 240  * Singly-linked Tail queue functions.
 241  */
 242 #define STAILQ_CONCAT(head1, head2) do {                                \
 243         if (!STAILQ_EMPTY((head2))) {                                   \
 244                 *(head1)->stqh_last = (head2)->stqh_first;              \
 245                 (head1)->stqh_last = (head2)->stqh_last;                \
 246                 STAILQ_INIT((head2));                                   \
 247         }                                                               \
 248 } while (0)
 249
 250 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 251
 252 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 253
 254 #define STAILQ_FOREACH(var, head, field)                                \
 255         for((var) = STAILQ_FIRST((head));                               \
 256            (var);                                                       \
 257            (var) = STAILQ_NEXT((var), field))
 258
 259
 260 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 261         for ((var) = STAILQ_FIRST((head));                              \
 262             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 263             (var) = (tvar))
 264
 265 #define STAILQ_INIT(head) do {                                          \
 266         STAILQ_FIRST((head)) = NULL;                                    \
 267         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 268 } while (0)
 269
 270 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 271         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 272                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 273         STAILQ_NEXT((tqelm), field) = (elm);                            \
 274 } while (0)
 275
 276 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 277         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 278                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 279         STAILQ_FIRST((head)) = (elm);                                   \
 280 } while (0)
 281
 282 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 283         STAILQ_NEXT((elm), field) = NULL;                               \
 284         *(head)->stqh_last = (elm);                                     \
 285         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 286 } while (0)
 287
 288 #define STAILQ_LAST(head, type, field)                                  \
 289         (STAILQ_EMPTY((head)) ?                                         \
 290                 NULL :                                                  \
 291                 ((struct type *)(void *)                                \
 292                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 293
 294 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 295
 296 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 297         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 298         if (STAILQ_FIRST((head)) == (elm)) {                            \
 299                 STAILQ_REMOVE_HEAD((head), field);                      \
 300         }                                                               \
 301         else {                                                          \
 302                 struct type *curelm = STAILQ_FIRST((head));             \
 303                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 304                         curelm = STAILQ_NEXT(curelm, field);            \
 305                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 306         }                                                               \
 307         TRASHIT(*oldnext);                                              \
 308 } while (0)
 309
 310 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 311         if ((STAILQ_FIRST((head)) =                                     \
 312              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 313                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 314 } while (0)
 315
 316 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 317         if ((STAILQ_NEXT(elm, field) =                                  \
 318              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 319                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 320 } while (0)
 321
 322 #define STAILQ_SWAP(head1, head2, type) do {                            \
 323         struct type *swap_first = STAILQ_FIRST(head1);                  \
 324         struct type **swap_last = (head1)->stqh_last;                   \
 325         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 326         (head1)->stqh_last = (head2)->stqh_last;                        \
 327         STAILQ_FIRST(head2) = swap_first;                               \
 328         (head2)->stqh_last = swap_last;                                 \
 329         if (STAILQ_EMPTY(head1))                                        \
 330                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 331         if (STAILQ_EMPTY(head2))                                        \
 332                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 333 } while (0)
 334
 335
 336 /*
 337  * List declarations.
 338  */
 339 #define LIST_HEAD(name, type)                                           \
 340 struct name {                                                           \
 341         struct type *lh_first;  /* first element */                     \
 342 }
 343
 344 #define LIST_HEAD_INITIALIZER(head)                                     \
 345         { NULL }
 346
 347 #define LIST_ENTRY(type)                                                \
 348 struct {                                                                \
 349         struct type *le_next;   /* next element */                      \
 350         struct type **le_prev;  /* address of previous next element */  \
 351 }
 352
 353 /*
 354  * List functions.
 355  */
 356
 357 #if (defined(_KERNEL) && defined(INVARIANTS))
 358 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 359         if (LIST_FIRST((head)) != NULL &&                               \
 360             LIST_FIRST((head))->field.le_prev !=                        \
 361              &LIST_FIRST((head)))                                       \
 362                 panic("Bad list head %p first->prev != head", (head));  \
 363 } while (0)
 364
 365 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 366         if (LIST_NEXT((elm), field) != NULL &&                          \
 367             LIST_NEXT((elm), field)->field.le_prev !=                   \
 368              &((elm)->field.le_next))                                   \
 369                 panic("Bad link elm %p next->prev != elm", (elm));      \
 370 } while (0)
 371
 372 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 373         if (*(elm)->field.le_prev != (elm))                             \
 374                 panic("Bad link elm %p prev->next != elm", (elm));      \
 375 } while (0)
 376 #else
 377 #define QMD_LIST_CHECK_HEAD(head, field)
 378 #define QMD_LIST_CHECK_NEXT(elm, field)
 379 #define QMD_LIST_CHECK_PREV(elm, field)
 380 #endif /* (_KERNEL && INVARIANTS) */
 381
 382 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 383
 384 #define LIST_FIRST(head)        ((head)->lh_first)
 385
 386 #define LIST_FOREACH(var, head, field)                                  \
 387         for ((var) = LIST_FIRST((head));                                \
 388             (var);                                                      \
 389             (var) = LIST_NEXT((var), field))
 390
 391 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 392         for ((var) = LIST_FIRST((head));                                \
 393             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 394             (var) = (tvar))
 395
 396 #define LIST_INIT(head) do {                                            \
 397         LIST_FIRST((head)) = NULL;                                      \
 398 } while (0)
 399
 400 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 401         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 402         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 403                 LIST_NEXT((listelm), field)->field.le_prev =            \
 404                     &LIST_NEXT((elm), field);                           \
 405         LIST_NEXT((listelm), field) = (elm);                            \
 406         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 407 } while (0)
 408
 409 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 410         QMD_LIST_CHECK_PREV(listelm, field);                            \
 411         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 412         LIST_NEXT((elm), field) = (listelm);                            \
 413         *(listelm)->field.le_prev = (elm);                              \
 414         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 415 } while (0)
 416
 417 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 418         QMD_LIST_CHECK_HEAD((head), field);                             \
 419         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 420                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 421         LIST_FIRST((head)) = (elm);                                     \
 422         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 423 } while (0)
 424
 425 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 426
 427 #define LIST_REMOVE(elm, field) do {                                    \
 428         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 429         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 430         QMD_LIST_CHECK_NEXT(elm, field);                                \
 431         QMD_LIST_CHECK_PREV(elm, field);                                \
 432         if (LIST_NEXT((elm), field) != NULL)                            \
 433                 LIST_NEXT((elm), field)->field.le_prev =                \
 434                     (elm)->field.le_prev;                               \
 435         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 436         TRASHIT(*oldnext);                                              \
 437         TRASHIT(*oldprev);                                              \
 438 } while (0)
 439
 440 #define LIST_SWAP(head1, head2, type, field) do {                       \
 441         struct type *swap_tmp = LIST_FIRST((head1));                    \
 442         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 443         LIST_FIRST((head2)) = swap_tmp;                                 \
 444         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 445                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 446         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 447                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 448 } while (0)
 449
 450 /*
 451  * Tail queue declarations.
 452  */
 453 #define TAILQ_HEAD(name, type)                                          \
 454 struct name {                                                           \
 455         struct type *tqh_first; /* first element */                     \
 456         struct type **tqh_last; /* addr of last next element */         \
 457         TRACEBUF                                                        \
 458 }
 459
 460 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 461         { NULL, &(head).tqh_first }
 462
 463 #define TAILQ_ENTRY(type)                                               \
 464 struct {                                                                \
 465         struct type *tqe_next;  /* next element */                      \
 466         struct type **tqe_prev; /* address of previous next element */  \
 467         TRACEBUF                                                        \
 468 }
 469
 470 /*
 471  * Tail queue functions.
 472  */
 473 #if (defined(_KERNEL) && defined(INVARIANTS))
 474 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 475         if (!TAILQ_EMPTY(head) &&                                       \
 476             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 477              &TAILQ_FIRST((head)))                                      \
 478                 panic("Bad tailq head %p first->prev != head", (head)); \
 479 } while (0)
 480
 481 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 482         if (*(head)->tqh_last != NULL)                                  \
 483                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 484 } while (0)
 485
 486 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 487         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 488             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 489              &((elm)->field.tqe_next))                                  \
 490                 panic("Bad link elm %p next->prev != elm", (elm));      \
 491 } while (0)
 492
 493 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 494         if (*(elm)->field.tqe_prev != (elm))                            \
 495                 panic("Bad link elm %p prev->next != elm", (elm));      \
 496 } while (0)
 497 #else
 498 #define QMD_TAILQ_CHECK_HEAD(head, field)
 499 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 500 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 501 #define QMD_TAILQ_CHECK_PREV(elm, field)
 502 #endif /* (_KERNEL && INVARIANTS) */
 503
 504 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 505         if (!TAILQ_EMPTY(head2)) {                                      \
 506                 *(head1)->tqh_last = (head2)->tqh_first;                \
 507                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 508                 (head1)->tqh_last = (head2)->tqh_last;                  \
 509                 TAILQ_INIT((head2));                                    \
 510                 QMD_TRACE_HEAD(head1);                                  \
 511                 QMD_TRACE_HEAD(head2);                                  \
 512         }                                                               \
 513 } while (0)
 514
 515 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 516
 517 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 518
 519 #define TAILQ_FOREACH(var, head, field)                                 \
 520         for ((var) = TAILQ_FIRST((head));                               \
 521             (var);                                                      \
 522             (var) = TAILQ_NEXT((var), field))
 523
 524 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 525         for ((var) = TAILQ_FIRST((head));                               \
 526             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 527             (var) = (tvar))
 528
 529 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 530         for ((var) = TAILQ_LAST((head), headname);                      \
 531             (var);                                                      \
 532             (var) = TAILQ_PREV((var), headname, field))
 533
 534 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 535         for ((var) = TAILQ_LAST((head), headname);                      \
 536             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 537             (var) = (tvar))
 538
 539 #define TAILQ_INIT(head) do {                                           \
 540         TAILQ_FIRST((head)) = NULL;                                     \
 541         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 542         QMD_TRACE_HEAD(head);                                           \
 543 } while (0)
 544
 545 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 546         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 547         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 548                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 549                     &TAILQ_NEXT((elm), field);                          \
 550         else {                                                          \
 551                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 552                 QMD_TRACE_HEAD(head);                                   \
 553         }                                                               \
 554         TAILQ_NEXT((listelm), field) = (elm);                           \
 555         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 556         QMD_TRACE_ELEM(&(elm)->field);                                  \
 557         QMD_TRACE_ELEM(&listelm->field);                                \
 558 } while (0)
 559
 560 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 561         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 562         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 563         TAILQ_NEXT((elm), field) = (listelm);                           \
 564         *(listelm)->field.tqe_prev = (elm);                             \
 565         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 566         QMD_TRACE_ELEM(&(elm)->field);                                  \
 567         QMD_TRACE_ELEM(&listelm->field);                                \
 568 } while (0)
 569
 570 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 571         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 572         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 573                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 574                     &TAILQ_NEXT((elm), field);                          \
 575         else                                                            \
 576                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 577         TAILQ_FIRST((head)) = (elm);                                    \
 578         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 579         QMD_TRACE_HEAD(head);                                           \
 580         QMD_TRACE_ELEM(&(elm)->field);                                  \
 581 } while (0)
 582
 583 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 584         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 585         TAILQ_NEXT((elm), field) = NULL;                                \
 586         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 587         *(head)->tqh_last = (elm);                                      \
 588         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 589         QMD_TRACE_HEAD(head);                                           \
 590         QMD_TRACE_ELEM(&(elm)->field);                                  \
 591 } while (0)
 592
 593 #define TAILQ_LAST(head, headname)                                      \
 594         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 595
 596 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 597
 598 #define TAILQ_PREV(elm, headname, field)                                \
 599         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 600
 601 #define TAILQ_REMOVE(head, elm, field) do {                             \
 602         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 603         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 604         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 605         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 606         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 607                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 608                     (elm)->field.tqe_prev;                              \
 609         else {                                                          \
 610                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 611                 QMD_TRACE_HEAD(head);                                   \
 612         }                                                               \
 613         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 614         TRASHIT(*oldnext);                                              \
 615         TRASHIT(*oldprev);                                              \
 616         QMD_TRACE_ELEM(&(elm)->field);                                  \
 617 } while (0)
 618
 619 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 620         struct type *swap_first = (head1)->tqh_first;                   \
 621         struct type **swap_last = (head1)->tqh_last;                    \
 622         (head1)->tqh_first = (head2)->tqh_first;                        \
 623         (head1)->tqh_last = (head2)->tqh_last;                          \
 624         (head2)->tqh_first = swap_first;                                \
 625         (head2)->tqh_last = swap_last;                                  \
 626         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 627                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 628         else                                                            \
 629                 (head1)->tqh_last = &(head1)->tqh_first;                \
 630         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 631                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 632         else                                                            \
 633                 (head2)->tqh_last = &(head2)->tqh_first;                \
 634 } while (0)
 635
 636 #endif /* !_SYS_QUEUE_H_ */