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   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: src/sys/sys/queue.h,v 1.68.2.4 2011/05/24 16:06:26 mdf Exp $
  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  * _SWAP                        +       +       +       +
 103  *
 104  */
 105 #ifdef QUEUE_MACRO_DEBUG
 106 /* Store the last 2 places the queue element or head was altered */
 107 struct qm_trace {
 108         char * lastfile;
 109         int lastline;
 110         char * prevfile;
 111         int prevline;
 112 };
 113
 114 #define TRACEBUF        struct qm_trace trace;
 115 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 116 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 117
 118 #define QMD_TRACE_HEAD(head) do {                                       \
 119         (head)->trace.prevline = (head)->trace.lastline;                \
 120         (head)->trace.prevfile = (head)->trace.lastfile;                \
 121         (head)->trace.lastline = __LINE__;                              \
 122         (head)->trace.lastfile = __FILE__;                              \
 123 } while (0)
 124
 125 #define QMD_TRACE_ELEM(elem) do {                                       \
 126         (elem)->trace.prevline = (elem)->trace.lastline;                \
 127         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 128         (elem)->trace.lastline = __LINE__;                              \
 129         (elem)->trace.lastfile = __FILE__;                              \
 130 } while (0)
 131
 132 #else
 133 #define QMD_TRACE_ELEM(elem)
 134 #define QMD_TRACE_HEAD(head)
 135 #define QMD_SAVELINK(name, link)
 136 #define TRACEBUF
 137 #define TRASHIT(x)
 138 #endif  /* QUEUE_MACRO_DEBUG */
 139
 140 /*
 141  * Singly-linked List declarations.
 142  */
 143 #define SLIST_HEAD(name, type)                                          \
 144 struct name {                                                           \
 145         struct type *slh_first; /* first element */                     \
 146 }
 147
 148 #define SLIST_HEAD_INITIALIZER(head)                                    \
 149         { NULL }
 150
 151 #define SLIST_ENTRY(type)                                               \
 152 struct {                                                                \
 153         struct type *sle_next;  /* next element */                      \
 154 }
 155
 156 /*
 157  * Singly-linked List functions.
 158  */
 159 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 160
 161 #define SLIST_FIRST(head)       ((head)->slh_first)
 162
 163 #define SLIST_FOREACH(var, head, field)                                 \
 164         for ((var) = SLIST_FIRST((head));                               \
 165             (var);                                                      \
 166             (var) = SLIST_NEXT((var), field))
 167
 168 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 169         for ((var) = SLIST_FIRST((head));                               \
 170             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 171             (var) = (tvar))
 172
 173 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 174         for ((varp) = &SLIST_FIRST((head));                             \
 175             ((var) = *(varp)) != NULL;                                  \
 176             (varp) = &SLIST_NEXT((var), field))
 177
 178 #define SLIST_INIT(head) do {                                           \
 179         SLIST_FIRST((head)) = NULL;                                     \
 180 } while (0)
 181
 182 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 183         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 184         SLIST_NEXT((slistelm), field) = (elm);                          \
 185 } while (0)
 186
 187 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 188         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 189         SLIST_FIRST((head)) = (elm);                                    \
 190 } while (0)
 191
 192 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 193
 194 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 195         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 196         if (SLIST_FIRST((head)) == (elm)) {                             \
 197                 SLIST_REMOVE_HEAD((head), field);                       \
 198         }                                                               \
 199         else {                                                          \
 200                 struct type *curelm = SLIST_FIRST((head));              \
 201                 while (SLIST_NEXT(curelm, field) != (elm))              \
 202                         curelm = SLIST_NEXT(curelm, field);             \
 203                 SLIST_REMOVE_AFTER(curelm, field);                      \
 204         }                                                               \
 205         TRASHIT(*oldnext);                                              \
 206 } while (0)
 207
 208 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 209         SLIST_NEXT(elm, field) =                                        \
 210             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 211 } while (0)
 212
 213 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 214         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 215 } while (0)
 216
 217 /*
 218  * Singly-linked Tail queue declarations.
 219  */
 220 #define STAILQ_HEAD(name, type)                                         \
 221 struct name {                                                           \
 222         struct type *stqh_first;/* first element */                     \
 223         struct type **stqh_last;/* addr of last next element */         \
 224 }
 225
 226 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 227         { NULL, &(head).stqh_first }
 228
 229 #define STAILQ_ENTRY(type)                                              \
 230 struct {                                                                \
 231         struct type *stqe_next; /* next element */                      \
 232 }
 233
 234 /*
 235  * Singly-linked Tail queue functions.
 236  */
 237 #define STAILQ_CONCAT(head1, head2) do {                                \
 238         if (!STAILQ_EMPTY((head2))) {                                   \
 239                 *(head1)->stqh_last = (head2)->stqh_first;              \
 240                 (head1)->stqh_last = (head2)->stqh_last;                \
 241                 STAILQ_INIT((head2));                                   \
 242         }                                                               \
 243 } while (0)
 244
 245 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 246
 247 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 248
 249 #define STAILQ_FOREACH(var, head, field)                                \
 250         for((var) = STAILQ_FIRST((head));                               \
 251            (var);                                                       \
 252            (var) = STAILQ_NEXT((var), field))
 253
 254
 255 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 256         for ((var) = STAILQ_FIRST((head));                              \
 257             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 258             (var) = (tvar))
 259
 260 #define STAILQ_INIT(head) do {                                          \
 261         STAILQ_FIRST((head)) = NULL;                                    \
 262         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 263 } while (0)
 264
 265 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 266         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 267                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 268         STAILQ_NEXT((tqelm), field) = (elm);                            \
 269 } while (0)
 270
 271 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 272         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 273                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 274         STAILQ_FIRST((head)) = (elm);                                   \
 275 } while (0)
 276
 277 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 278         STAILQ_NEXT((elm), field) = NULL;                               \
 279         *(head)->stqh_last = (elm);                                     \
 280         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 281 } while (0)
 282
 283 #define STAILQ_LAST(head, type, field)                                  \
 284         (STAILQ_EMPTY((head)) ?                                         \
 285                 NULL :                                                  \
 286                 ((struct type *)(void *)                                \
 287                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 288
 289 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 290
 291 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 292         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 293         if (STAILQ_FIRST((head)) == (elm)) {                            \
 294                 STAILQ_REMOVE_HEAD((head), field);                      \
 295         }                                                               \
 296         else {                                                          \
 297                 struct type *curelm = STAILQ_FIRST((head));             \
 298                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 299                         curelm = STAILQ_NEXT(curelm, field);            \
 300                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 301         }                                                               \
 302         TRASHIT(*oldnext);                                              \
 303 } while (0)
 304
 305 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 306         if ((STAILQ_NEXT(elm, field) =                                  \
 307              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 308                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 309 } while (0)
 310
 311 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 312         if ((STAILQ_FIRST((head)) =                                     \
 313              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 314                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 315 } while (0)
 316
 317 #define STAILQ_SWAP(head1, head2, type) do {                            \
 318         struct type *swap_first = STAILQ_FIRST(head1);                  \
 319         struct type **swap_last = (head1)->stqh_last;                   \
 320         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 321         (head1)->stqh_last = (head2)->stqh_last;                        \
 322         STAILQ_FIRST(head2) = swap_first;                               \
 323         (head2)->stqh_last = swap_last;                                 \
 324         if (STAILQ_EMPTY(head1))                                        \
 325                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 326         if (STAILQ_EMPTY(head2))                                        \
 327                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 328 } while (0)
 329
 330
 331 /*
 332  * List declarations.
 333  */
 334 #define LIST_HEAD(name, type)                                           \
 335 struct name {                                                           \
 336         struct type *lh_first;  /* first element */                     \
 337 }
 338
 339 #define LIST_HEAD_INITIALIZER(head)                                     \
 340         { NULL }
 341
 342 #define LIST_ENTRY(type)                                                \
 343 struct {                                                                \
 344         struct type *le_next;   /* next element */                      \
 345         struct type **le_prev;  /* address of previous next element */  \
 346 }
 347
 348 /*
 349  * List functions.
 350  */
 351
 352 #if (defined(_KERNEL) && defined(INVARIANTS))
 353 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 354         if (LIST_FIRST((head)) != NULL &&                               \
 355             LIST_FIRST((head))->field.le_prev !=                        \
 356              &LIST_FIRST((head)))                                       \
 357                 panic("Bad list head %p first->prev != head", (head));  \
 358 } while (0)
 359
 360 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 361         if (LIST_NEXT((elm), field) != NULL &&                          \
 362             LIST_NEXT((elm), field)->field.le_prev !=                   \
 363              &((elm)->field.le_next))                                   \
 364                 panic("Bad link elm %p next->prev != elm", (elm));      \
 365 } while (0)
 366
 367 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 368         if (*(elm)->field.le_prev != (elm))                             \
 369                 panic("Bad link elm %p prev->next != elm", (elm));      \
 370 } while (0)
 371 #else
 372 #define QMD_LIST_CHECK_HEAD(head, field)
 373 #define QMD_LIST_CHECK_NEXT(elm, field)
 374 #define QMD_LIST_CHECK_PREV(elm, field)
 375 #endif /* (_KERNEL && INVARIANTS) */
 376
 377 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 378
 379 #define LIST_FIRST(head)        ((head)->lh_first)
 380
 381 #define LIST_FOREACH(var, head, field)                                  \
 382         for ((var) = LIST_FIRST((head));                                \
 383             (var);                                                      \
 384             (var) = LIST_NEXT((var), field))
 385
 386 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 387         for ((var) = LIST_FIRST((head));                                \
 388             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 389             (var) = (tvar))
 390
 391 #define LIST_INIT(head) do {                                            \
 392         LIST_FIRST((head)) = NULL;                                      \
 393 } while (0)
 394
 395 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 396         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 397         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 398                 LIST_NEXT((listelm), field)->field.le_prev =            \
 399                     &LIST_NEXT((elm), field);                           \
 400         LIST_NEXT((listelm), field) = (elm);                            \
 401         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 402 } while (0)
 403
 404 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 405         QMD_LIST_CHECK_PREV(listelm, field);                            \
 406         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 407         LIST_NEXT((elm), field) = (listelm);                            \
 408         *(listelm)->field.le_prev = (elm);                              \
 409         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 410 } while (0)
 411
 412 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 413         QMD_LIST_CHECK_HEAD((head), field);                             \
 414         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 415                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 416         LIST_FIRST((head)) = (elm);                                     \
 417         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 418 } while (0)
 419
 420 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 421
 422 #define LIST_REMOVE(elm, field) do {                                    \
 423         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 424         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 425         QMD_LIST_CHECK_NEXT(elm, field);                                \
 426         QMD_LIST_CHECK_PREV(elm, field);                                \
 427         if (LIST_NEXT((elm), field) != NULL)                            \
 428                 LIST_NEXT((elm), field)->field.le_prev =                \
 429                     (elm)->field.le_prev;                               \
 430         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 431         TRASHIT(*oldnext);                                              \
 432         TRASHIT(*oldprev);                                              \
 433 } while (0)
 434
 435 #define LIST_SWAP(head1, head2, type, field) do {                       \
 436         struct type *swap_tmp = LIST_FIRST((head1));                    \
 437         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 438         LIST_FIRST((head2)) = swap_tmp;                                 \
 439         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 440                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 441         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 442                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 443 } while (0)
 444
 445 /*
 446  * Tail queue declarations.
 447  */
 448 #define TAILQ_HEAD(name, type)                                          \
 449 struct name {                                                           \
 450         struct type *tqh_first; /* first element */                     \
 451         struct type **tqh_last; /* addr of last next element */         \
 452         TRACEBUF                                                        \
 453 }
 454
 455 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 456         { NULL, &(head).tqh_first }
 457
 458 #define TAILQ_ENTRY(type)                                               \
 459 struct {                                                                \
 460         struct type *tqe_next;  /* next element */                      \
 461         struct type **tqe_prev; /* address of previous next element */  \
 462         TRACEBUF                                                        \
 463 }
 464
 465 /*
 466  * Tail queue functions.
 467  */
 468 #if (defined(_KERNEL) && defined(INVARIANTS))
 469 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 470         if (!TAILQ_EMPTY(head) &&                                       \
 471             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 472              &TAILQ_FIRST((head)))                                      \
 473                 panic("Bad tailq head %p first->prev != head", (head)); \
 474 } while (0)
 475
 476 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 477         if (*(head)->tqh_last != NULL)                                  \
 478                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 479 } while (0)
 480
 481 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 482         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 483             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 484              &((elm)->field.tqe_next))                                  \
 485                 panic("Bad link elm %p next->prev != elm", (elm));      \
 486 } while (0)
 487
 488 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 489         if (*(elm)->field.tqe_prev != (elm))                            \
 490                 panic("Bad link elm %p prev->next != elm", (elm));      \
 491 } while (0)
 492 #else
 493 #define QMD_TAILQ_CHECK_HEAD(head, field)
 494 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 495 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 496 #define QMD_TAILQ_CHECK_PREV(elm, field)
 497 #endif /* (_KERNEL && INVARIANTS) */
 498
 499 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 500         if (!TAILQ_EMPTY(head2)) {                                      \
 501                 *(head1)->tqh_last = (head2)->tqh_first;                \
 502                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 503                 (head1)->tqh_last = (head2)->tqh_last;                  \
 504                 TAILQ_INIT((head2));                                    \
 505                 QMD_TRACE_HEAD(head1);                                  \
 506                 QMD_TRACE_HEAD(head2);                                  \
 507         }                                                               \
 508 } while (0)
 509
 510 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 511
 512 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 513
 514 #define TAILQ_FOREACH(var, head, field)                                 \
 515         for ((var) = TAILQ_FIRST((head));                               \
 516             (var);                                                      \
 517             (var) = TAILQ_NEXT((var), field))
 518
 519 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 520         for ((var) = TAILQ_FIRST((head));                               \
 521             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 522             (var) = (tvar))
 523
 524 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 525         for ((var) = TAILQ_LAST((head), headname);                      \
 526             (var);                                                      \
 527             (var) = TAILQ_PREV((var), headname, field))
 528
 529 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 530         for ((var) = TAILQ_LAST((head), headname);                      \
 531             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 532             (var) = (tvar))
 533
 534 #define TAILQ_INIT(head) do {                                           \
 535         TAILQ_FIRST((head)) = NULL;                                     \
 536         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 537         QMD_TRACE_HEAD(head);                                           \
 538 } while (0)
 539
 540 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 541         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 542         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 543                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 544                     &TAILQ_NEXT((elm), field);                          \
 545         else {                                                          \
 546                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 547                 QMD_TRACE_HEAD(head);                                   \
 548         }                                                               \
 549         TAILQ_NEXT((listelm), field) = (elm);                           \
 550         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 551         QMD_TRACE_ELEM(&(elm)->field);                                  \
 552         QMD_TRACE_ELEM(&listelm->field);                                \
 553 } while (0)
 554
 555 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 556         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 557         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 558         TAILQ_NEXT((elm), field) = (listelm);                           \
 559         *(listelm)->field.tqe_prev = (elm);                             \
 560         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 561         QMD_TRACE_ELEM(&(elm)->field);                                  \
 562         QMD_TRACE_ELEM(&listelm->field);                                \
 563 } while (0)
 564
 565 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 566         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 567         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 568                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 569                     &TAILQ_NEXT((elm), field);                          \
 570         else                                                            \
 571                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 572         TAILQ_FIRST((head)) = (elm);                                    \
 573         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 574         QMD_TRACE_HEAD(head);                                           \
 575         QMD_TRACE_ELEM(&(elm)->field);                                  \
 576 } while (0)
 577
 578 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 579         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 580         TAILQ_NEXT((elm), field) = NULL;                                \
 581         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 582         *(head)->tqh_last = (elm);                                      \
 583         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 584         QMD_TRACE_HEAD(head);                                           \
 585         QMD_TRACE_ELEM(&(elm)->field);                                  \
 586 } while (0)
 587
 588 #define TAILQ_LAST(head, headname)                                      \
 589         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 590
 591 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 592
 593 #define TAILQ_PREV(elm, headname, field)                                \
 594         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 595
 596 #define TAILQ_REMOVE(head, elm, field) do {                             \
 597         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 598         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 599         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 600         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 601         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 602                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 603                     (elm)->field.tqe_prev;                              \
 604         else {                                                          \
 605                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 606                 QMD_TRACE_HEAD(head);                                   \
 607         }                                                               \
 608         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 609         TRASHIT(*oldnext);                                              \
 610         TRASHIT(*oldprev);                                              \
 611         QMD_TRACE_ELEM(&(elm)->field);                                  \
 612 } while (0)
 613
 614 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 615         struct type *swap_first = (head1)->tqh_first;                   \
 616         struct type **swap_last = (head1)->tqh_last;                    \
 617         (head1)->tqh_first = (head2)->tqh_first;                        \
 618         (head1)->tqh_last = (head2)->tqh_last;                          \
 619         (head2)->tqh_first = swap_first;                                \
 620         (head2)->tqh_last = swap_last;                                  \
 621         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 622                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 623         else                                                            \
 624                 (head1)->tqh_last = &(head1)->tqh_first;                \
 625         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 626                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 627         else                                                            \
 628                 (head2)->tqh_last = &(head2)->tqh_first;                \
 629 } while (0)
 630
 631 #ifdef _KERNEL
 632
 633 /*
 634  * XXX insque() and remque() are an old way of handling certain queues.
 635  * They bogusly assumes that all queue heads look alike.
 636  */
 637
 638 struct quehead {
 639         struct quehead *qh_link;
 640         struct quehead *qh_rlink;
 641 };
 642
 643 #ifdef __CC_SUPPORTS___INLINE
 644
 645 static __inline void
 646 insque(void *a, void *b)
 647 {
 648         struct quehead *element = (struct quehead *)a,
 649                  *head = (struct quehead *)b;
 650
 651         element->qh_link = head->qh_link;
 652         element->qh_rlink = head;
 653         head->qh_link = element;
 654         element->qh_link->qh_rlink = element;
 655 }
 656
 657 static __inline void
 658 remque(void *a)
 659 {
 660         struct quehead *element = (struct quehead *)a;
 661
 662         element->qh_link->qh_rlink = element->qh_rlink;
 663         element->qh_rlink->qh_link = element->qh_link;
 664         element->qh_rlink = 0;
 665 }
 666
 667 #else /* !__CC_SUPPORTS___INLINE */
 668
 669 void    insque(void *a, void *b);
 670 void    remque(void *a);
 671
 672 #endif /* __CC_SUPPORTS___INLINE */
 673
 674 #endif /* _KERNEL */
 675
 676 #endif /* !_SYS_QUEUE_H_ */