kern/include/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 #pragma once
  34
  35 #include <ros/common.h>    /* for __offsetof */
  36
  37 /*
  38  * This file defines four types of data structures: singly-linked lists,
  39  * singly-linked tail queues, lists and tail queues.
  40  *
  41  * A singly-linked list is headed by a single forward pointer. The elements
  42  * are singly linked for minimum space and pointer manipulation overhead at
  43  * the expense of O(n) removal for arbitrary elements. New elements can be
  44  * added to the list after an existing element or at the head of the list.
  45  * Elements being removed from the head of the list should use the explicit
  46  * macro for this purpose for optimum efficiency. A singly-linked list may
  47  * only be traversed in the forward direction.  Singly-linked lists are ideal
  48  * for applications with large datasets and few or no removals or for
  49  * implementing a LIFO queue.
  50  *
  51  * A singly-linked tail queue is headed by a pair of pointers, one to the
  52  * head of the list and the other to the tail of the list. The elements are
  53  * singly linked for minimum space and pointer manipulation overhead at the
  54  * expense of O(n) removal for arbitrary elements. New elements can be added
  55  * to the list after an existing element, at the head of the list, or at the
  56  * end of the list. Elements being removed from the head of the tail queue
  57  * should use the explicit macro for this purpose for optimum efficiency.
  58  * A singly-linked tail queue may only be traversed in the forward direction.
  59  * Singly-linked tail queues are ideal for applications with large datasets
  60  * and few or no removals or for implementing a FIFO queue.
  61  *
  62  * A list is headed by a single forward pointer (or an array of forward
  63  * pointers for a hash table header). The elements are doubly linked
  64  * so that an arbitrary element can be removed without a need to
  65  * traverse the list. New elements can be added to the list before
  66  * or after an existing element or at the head of the list. A list
  67  * may only be traversed in the forward direction.
  68  *
  69  * A tail queue is headed by a pair of pointers, one to the head of the
  70  * list and the other to the tail of the list. The elements are doubly
  71  * linked so that an arbitrary element can be removed without a need to
  72  * traverse the list. New elements can be added to the list before or
  73  * after an existing element, at the head of the list, or at the end of
  74  * the list. A tail queue may be traversed in either direction.
  75  *
  76  * For details on the use of these macros, see the queue(3) manual page.
  77  *
  78  *
  79  *                              SLIST   LIST    STAILQ  TAILQ
  80  * _HEAD                        +       +       +       +
  81  * _HEAD_INITIALIZER            +       +       +       +
  82  * _ENTRY                       +       +       +       +
  83  * _INIT                        +       +       +       +
  84  * _EMPTY                       +       +       +       +
  85  * _FIRST                       +       +       +       +
  86  * _NEXT                        +       +       +       +
  87  * _PREV                        -       -       -       +
  88  * _LAST                        -       -       +       +
  89  * _FOREACH                     +       +       +       +
  90  * _FOREACH_SAFE                +       +       +       +
  91  * _FOREACH_REVERSE             -       -       -       +
  92  * _FOREACH_REVERSE_SAFE        -       -       -       +
  93  * _INSERT_HEAD                 +       +       +       +
  94  * _INSERT_BEFORE               -       +       -       +
  95  * _INSERT_AFTER                +       +       +       +
  96  * _INSERT_TAIL                 -       -       +       +
  97  * _CONCAT                      -       -       +       +
  98  * _REMOVE_AFTER                +       -       +       -
  99  * _REMOVE_HEAD                 +       -       +       -
 100  * _REMOVE                      +       +       +       +
 101  *
 102  */
 103 #ifdef QUEUE_MACRO_DEBUG
 104 /* ROS has TAILQ-sized elements in a vcore, exposed to userspace via the
 105  * vcoremap.  If you have QM tracing turned on, you'll mess it up. */
 106 #error "Don't use sys/queue QUEUE_MACRO_DEBUG without dealing with the vcoremap"
 107 /* Store the last 2 places the queue element or head was altered */
 108 struct qm_trace {
 109         char * lastfile;
 110         int lastline;
 111         char * prevfile;
 112         int prevline;
 113 };
 114
 115 #define TRACEBUF        struct qm_trace trace;
 116 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 117 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 118
 119 #define QMD_TRACE_HEAD(head) do {                                       \
 120         (head)->trace.prevline = (head)->trace.lastline;                \
 121         (head)->trace.prevfile = (head)->trace.lastfile;                \
 122         (head)->trace.lastline = __LINE__;                              \
 123         (head)->trace.lastfile = __FILE__;                              \
 124 } while (0)
 125
 126 #define QMD_TRACE_ELEM(elem) do {                                       \
 127         (elem)->trace.prevline = (elem)->trace.lastline;                \
 128         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 129         (elem)->trace.lastline = __LINE__;                              \
 130         (elem)->trace.lastfile = __FILE__;                              \
 131 } while (0)
 132
 133 #else
 134 #define QMD_TRACE_ELEM(elem)
 135 #define QMD_TRACE_HEAD(head)
 136 #define QMD_SAVELINK(name, link)
 137 #define TRACEBUF
 138 #define TRASHIT(x)
 139 #endif  /* QUEUE_MACRO_DEBUG */
 140
 141 /*
 142  * Singly-linked List declarations.
 143  */
 144 #define SLIST_HEAD(name, type)                                          \
 145 struct name {                                                           \
 146         struct type *slh_first; /* first element */                     \
 147 }
 148
 149 #define SLIST_HEAD_INITIALIZER(head)                                    \
 150         { NULL }
 151
 152 #define SLIST_ENTRY(type)                                               \
 153 struct {                                                                \
 154         struct type *sle_next;  /* next element */                      \
 155 }
 156
 157 /*
 158  * Singly-linked List functions.
 159  */
 160 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 161
 162 #define SLIST_FIRST(head)       ((head)->slh_first)
 163
 164 #define SLIST_FOREACH(var, head, field)                                 \
 165         for ((var) = SLIST_FIRST((head));                               \
 166             (var);                                                      \
 167             (var) = SLIST_NEXT((var), field))
 168
 169 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 170         for ((var) = SLIST_FIRST((head));                               \
 171             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 172             (var) = (tvar))
 173
 174 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 175         for ((varp) = &SLIST_FIRST((head));                             \
 176             ((var) = *(varp)) != NULL;                                  \
 177             (varp) = &SLIST_NEXT((var), field))
 178
 179 #define SLIST_INIT(head) do {                                           \
 180         SLIST_FIRST((head)) = NULL;                                     \
 181 } while (0)
 182
 183 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 184         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 185         SLIST_NEXT((slistelm), field) = (elm);                          \
 186 } while (0)
 187
 188 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 189         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 190         SLIST_FIRST((head)) = (elm);                                    \
 191 } while (0)
 192
 193 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 194
 195 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 196         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 197         if (SLIST_FIRST((head)) == (elm)) {                             \
 198                 SLIST_REMOVE_HEAD((head), field);                       \
 199         }                                                               \
 200         else {                                                          \
 201                 struct type *curelm = SLIST_FIRST((head));              \
 202                 while (SLIST_NEXT(curelm, field) != (elm))              \
 203                         curelm = SLIST_NEXT(curelm, field);             \
 204                 SLIST_REMOVE_AFTER(curelm, field);                      \
 205         }                                                               \
 206         TRASHIT(*oldnext);                                              \
 207 } while (0)
 208
 209 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 210         SLIST_NEXT(elm, field) =                                        \
 211             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 212 } while (0)
 213
 214 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 215         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 216 } while (0)
 217
 218 /*
 219  * Singly-linked Tail queue declarations.
 220  */
 221 #define STAILQ_HEAD(name, type)                                         \
 222 struct name {                                                           \
 223         struct type *stqh_first;/* first element */                     \
 224         struct type **stqh_last;/* addr of last next element */         \
 225 }
 226
 227 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 228         { NULL, &(head).stqh_first }
 229
 230 #define STAILQ_ENTRY(type)                                              \
 231 struct {                                                                \
 232         struct type *stqe_next; /* next element */                      \
 233 }
 234
 235 /*
 236  * Singly-linked Tail queue functions.
 237  */
 238 #define STAILQ_CONCAT(head1, head2) do {                                \
 239         if (!STAILQ_EMPTY((head2))) {                                   \
 240                 *(head1)->stqh_last = (head2)->stqh_first;              \
 241                 (head1)->stqh_last = (head2)->stqh_last;                \
 242                 STAILQ_INIT((head2));                                   \
 243         }                                                               \
 244 } while (0)
 245
 246 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 247
 248 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 249
 250 #define STAILQ_FOREACH(var, head, field)                                \
 251         for((var) = STAILQ_FIRST((head));                               \
 252            (var);                                                       \
 253            (var) = STAILQ_NEXT((var), field))
 254
 255
 256 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 257         for ((var) = STAILQ_FIRST((head));                              \
 258             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 259             (var) = (tvar))
 260
 261 #define STAILQ_INIT(head) do {                                          \
 262         STAILQ_FIRST((head)) = NULL;                                    \
 263         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 264 } while (0)
 265
 266 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 267         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 268                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 269         STAILQ_NEXT((tqelm), field) = (elm);                            \
 270 } while (0)
 271
 272 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 273         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 274                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 275         STAILQ_FIRST((head)) = (elm);                                   \
 276 } while (0)
 277
 278 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 279         STAILQ_NEXT((elm), field) = NULL;                               \
 280         *(head)->stqh_last = (elm);                                     \
 281         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 282 } while (0)
 283
 284 #define STAILQ_LAST(head, type, field)                                  \
 285         (STAILQ_EMPTY((head)) ?                                         \
 286                 NULL :                                                  \
 287                 ((struct type *)(void *)                                \
 288                 ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 289
 290 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 291
 292 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 293         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 294         if (STAILQ_FIRST((head)) == (elm)) {                            \
 295                 STAILQ_REMOVE_HEAD((head), field);                      \
 296         }                                                               \
 297         else {                                                          \
 298                 struct type *curelm = STAILQ_FIRST((head));             \
 299                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 300                         curelm = STAILQ_NEXT(curelm, field);            \
 301                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 302         }                                                               \
 303         TRASHIT(*oldnext);                                              \
 304 } while (0)
 305
 306 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 307         if ((STAILQ_FIRST((head)) =                                     \
 308              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 309                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 310 } while (0)
 311
 312 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 313         if ((STAILQ_NEXT(elm, field) =                                  \
 314              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 315                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 316 } while (0)
 317
 318 #define STAILQ_SWAP(head1, head2, type) do {                            \
 319         struct type *swap_first = STAILQ_FIRST(head1);                  \
 320         struct type **swap_last = (head1)->stqh_last;                   \
 321         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 322         (head1)->stqh_last = (head2)->stqh_last;                        \
 323         STAILQ_FIRST(head2) = swap_first;                               \
 324         (head2)->stqh_last = swap_last;                                 \
 325         if (STAILQ_EMPTY(head1))                                        \
 326                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 327         if (STAILQ_EMPTY(head2))                                        \
 328                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 329 } while (0)
 330
 331
 332 /*
 333  * List declarations.
 334  */
 335 #define BSD_LIST_HEAD(name, type)                                               \
 336 struct name {                                                           \
 337         struct type *lh_first;  /* first element */                     \
 338 }
 339
 340 #define BSD_LIST_HEAD_INITIALIZER(head)                                 \
 341         { NULL }
 342
 343 #define BSD_LIST_ENTRY(type)                                            \
 344 struct {                                                                \
 345         struct type *le_next;   /* next element */                      \
 346         struct type **le_prev;  /* address of previous next element */  \
 347 }
 348
 349 /*
 350  * List functions.
 351  */
 352
 353 #if (defined(_KERNEL) && defined(INVARIANTS))
 354 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 355         if (BSD_LIST_FIRST((head)) != NULL &&                           \
 356             BSD_LIST_FIRST((head))->field.le_prev !=                    \
 357              &BSD_LIST_FIRST((head)))                                   \
 358                 panic("Bad list head %p first->prev != head", (head));  \
 359 } while (0)
 360
 361 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 362         if (BSD_LIST_NEXT((elm), field) != NULL &&                              \
 363             BSD_LIST_NEXT((elm), field)->field.le_prev !=                       \
 364              &((elm)->field.le_next))                                   \
 365                 panic("Bad link elm %p next->prev != elm", (elm));      \
 366 } while (0)
 367
 368 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 369         if (*(elm)->field.le_prev != (elm))                             \
 370                 panic("Bad link elm %p prev->next != elm", (elm));      \
 371 } while (0)
 372 #else
 373 #define QMD_LIST_CHECK_HEAD(head, field)
 374 #define QMD_LIST_CHECK_NEXT(elm, field)
 375 #define QMD_LIST_CHECK_PREV(elm, field)
 376 #endif /* (_KERNEL && INVARIANTS) */
 377
 378 #define BSD_LIST_EMPTY(head)    ((head)->lh_first == NULL)
 379
 380 #define BSD_LIST_FIRST(head)    ((head)->lh_first)
 381
 382 #define BSD_LIST_FOREACH(var, head, field)                                      \
 383         for ((var) = BSD_LIST_FIRST((head));                            \
 384             (var);                                                      \
 385             (var) = BSD_LIST_NEXT((var), field))
 386
 387 #define BSD_LIST_FOREACH_SAFE(var, head, field, tvar)                   \
 388         for ((var) = BSD_LIST_FIRST((head));                            \
 389             (var) && ((tvar) = BSD_LIST_NEXT((var), field), 1);         \
 390             (var) = (tvar))
 391
 392 #define BSD_LIST_INIT(head) do {                                                \
 393         BSD_LIST_FIRST((head)) = NULL;                                  \
 394 } while (0)
 395
 396 #define BSD_LIST_INSERT_AFTER(listelm, elm, field) do {                 \
 397         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 398         if ((BSD_LIST_NEXT((elm), field) = BSD_LIST_NEXT((listelm), field)) != NULL)\
 399                 BSD_LIST_NEXT((listelm), field)->field.le_prev =                \
 400                     &BSD_LIST_NEXT((elm), field);                               \
 401         BSD_LIST_NEXT((listelm), field) = (elm);                                \
 402         (elm)->field.le_prev = &BSD_LIST_NEXT((listelm), field);                \
 403 } while (0)
 404
 405 #define BSD_LIST_INSERT_BEFORE(listelm, elm, field) do {                        \
 406         QMD_LIST_CHECK_PREV(listelm, field);                            \
 407         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 408         BSD_LIST_NEXT((elm), field) = (listelm);                                \
 409         *(listelm)->field.le_prev = (elm);                              \
 410         (listelm)->field.le_prev = &BSD_LIST_NEXT((elm), field);                \
 411 } while (0)
 412
 413 #define BSD_LIST_INSERT_HEAD(head, elm, field) do {                             \
 414         QMD_LIST_CHECK_HEAD((head), field);                             \
 415         if ((BSD_LIST_NEXT((elm), field) = BSD_LIST_FIRST((head))) != NULL)     \
 416                 BSD_LIST_FIRST((head))->field.le_prev = &BSD_LIST_NEXT((elm), field);\
 417         BSD_LIST_FIRST((head)) = (elm);                                 \
 418         (elm)->field.le_prev = &BSD_LIST_FIRST((head));                 \
 419 } while (0)
 420
 421 #define BSD_LIST_NEXT(elm, field)       ((elm)->field.le_next)
 422
 423 #define BSD_LIST_PREV(elm, head, type, field)                   \
 424         ((elm)->field.le_prev == &BSD_LIST_FIRST((head)) ? NULL :       \
 425             container_of((elm)->field.le_prev,                  \
 426             struct type, field.le_next))
 427
 428 #define BSD_LIST_REMOVE(elm, field) do {                                        \
 429         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 430         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 431         QMD_LIST_CHECK_NEXT(elm, field);                                \
 432         QMD_LIST_CHECK_PREV(elm, field);                                \
 433         if (BSD_LIST_NEXT((elm), field) != NULL)                                \
 434                 BSD_LIST_NEXT((elm), field)->field.le_prev =            \
 435                     (elm)->field.le_prev;                               \
 436         *(elm)->field.le_prev = BSD_LIST_NEXT((elm), field);            \
 437         TRASHIT(*oldnext);                                              \
 438         TRASHIT(*oldprev);                                              \
 439 } while (0)
 440
 441 #define BSD_LIST_SWAP(head1, head2, type, field) do {                   \
 442         struct type *swap_tmp = BSD_LIST_FIRST((head1));                        \
 443         BSD_LIST_FIRST((head1)) = BSD_LIST_FIRST((head2));                      \
 444         BSD_LIST_FIRST((head2)) = swap_tmp;                                     \
 445         if ((swap_tmp = BSD_LIST_FIRST((head1))) != NULL)                       \
 446                 swap_tmp->field.le_prev = &BSD_LIST_FIRST((head1));             \
 447         if ((swap_tmp = BSD_LIST_FIRST((head2))) != NULL)                       \
 448                 swap_tmp->field.le_prev = &BSD_LIST_FIRST((head2));             \
 449 } while (0)
 450
 451 /*
 452  * Tail queue declarations.
 453  */
 454 #define TAILQ_HEAD(name, type)                                          \
 455 struct name {                                                           \
 456         struct type *tqh_first; /* first element */                     \
 457         struct type **tqh_last; /* addr of last next element */         \
 458         TRACEBUF                                                        \
 459 }
 460
 461 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 462         { NULL, &(head).tqh_first }
 463
 464 #define TAILQ_ENTRY(type)                                               \
 465 struct {                                                                \
 466         struct type *tqe_next;  /* next element */                      \
 467         struct type **tqe_prev; /* address of previous next element */  \
 468         TRACEBUF                                                        \
 469 }
 470
 471 /*
 472  * Tail queue functions.
 473  */
 474 #if (defined(_KERNEL) && defined(INVARIANTS))
 475 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 476         if (!TAILQ_EMPTY(head) &&                                       \
 477             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 478              &TAILQ_FIRST((head)))                                      \
 479                 panic("Bad tailq head %p first->prev != head", (head)); \
 480 } while (0)
 481
 482 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 483         if (*(head)->tqh_last != NULL)                                  \
 484                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 485 } while (0)
 486
 487 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 488         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 489             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 490              &((elm)->field.tqe_next))                                  \
 491                 panic("Bad link elm %p next->prev != elm", (elm));      \
 492 } while (0)
 493
 494 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 495         if (*(elm)->field.tqe_prev != (elm))                            \
 496                 panic("Bad link elm %p prev->next != elm", (elm));      \
 497 } while (0)
 498 #else
 499 #define QMD_TAILQ_CHECK_HEAD(head, field)
 500 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 501 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 502 #define QMD_TAILQ_CHECK_PREV(elm, field)
 503 #endif /* (_KERNEL && INVARIANTS) */
 504
 505 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 506         if (!TAILQ_EMPTY(head2)) {                                      \
 507                 *(head1)->tqh_last = (head2)->tqh_first;                \
 508                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 509                 (head1)->tqh_last = (head2)->tqh_last;                  \
 510                 TAILQ_INIT((head2));                                    \
 511                 QMD_TRACE_HEAD(head1);                                  \
 512                 QMD_TRACE_HEAD(head2);                                  \
 513         }                                                               \
 514 } while (0)
 515
 516 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 517
 518 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 519
 520 #define TAILQ_FOREACH(var, head, field)                                 \
 521         for ((var) = TAILQ_FIRST((head));                               \
 522             (var);                                                      \
 523             (var) = TAILQ_NEXT((var), field))
 524
 525 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 526         for ((var) = TAILQ_FIRST((head));                               \
 527             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 528             (var) = (tvar))
 529
 530 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 531         for ((var) = TAILQ_LAST((head), headname);                      \
 532             (var);                                                      \
 533             (var) = TAILQ_PREV((var), headname, field))
 534
 535 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 536         for ((var) = TAILQ_LAST((head), headname);                      \
 537             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 538             (var) = (tvar))
 539
 540 #define TAILQ_INIT(head) do {                                           \
 541         TAILQ_FIRST((head)) = NULL;                                     \
 542         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 543         QMD_TRACE_HEAD(head);                                           \
 544 } while (0)
 545
 546 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 547         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 548         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 549                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 550                     &TAILQ_NEXT((elm), field);                          \
 551         else {                                                          \
 552                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 553                 QMD_TRACE_HEAD(head);                                   \
 554         }                                                               \
 555         TAILQ_NEXT((listelm), field) = (elm);                           \
 556         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 557         QMD_TRACE_ELEM(&(elm)->field);                                  \
 558         QMD_TRACE_ELEM(&listelm->field);                                \
 559 } while (0)
 560
 561 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 562         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 563         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 564         TAILQ_NEXT((elm), field) = (listelm);                           \
 565         *(listelm)->field.tqe_prev = (elm);                             \
 566         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 567         QMD_TRACE_ELEM(&(elm)->field);                                  \
 568         QMD_TRACE_ELEM(&listelm->field);                                \
 569 } while (0)
 570
 571 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 572         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 573         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 574                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 575                     &TAILQ_NEXT((elm), field);                          \
 576         else                                                            \
 577                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 578         TAILQ_FIRST((head)) = (elm);                                    \
 579         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 580         QMD_TRACE_HEAD(head);                                           \
 581         QMD_TRACE_ELEM(&(elm)->field);                                  \
 582 } while (0)
 583
 584 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 585         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 586         TAILQ_NEXT((elm), field) = NULL;                                \
 587         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 588         *(head)->tqh_last = (elm);                                      \
 589         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 590         QMD_TRACE_HEAD(head);                                           \
 591         QMD_TRACE_ELEM(&(elm)->field);                                  \
 592 } while (0)
 593
 594 #define TAILQ_LAST(head, headname)                                      \
 595         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 596
 597 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 598
 599 #define TAILQ_PREV(elm, headname, field)                                \
 600         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 601
 602 #define TAILQ_REMOVE(head, elm, field) do {                             \
 603         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 604         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 605         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 606         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 607         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 608                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 609                     (elm)->field.tqe_prev;                              \
 610         else {                                                          \
 611                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 612                 QMD_TRACE_HEAD(head);                                   \
 613         }                                                               \
 614         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 615         TRASHIT(*oldnext);                                              \
 616         TRASHIT(*oldprev);                                              \
 617         QMD_TRACE_ELEM(&(elm)->field);                                  \
 618 } while (0)
 619
 620 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 621         struct type *swap_first = (head1)->tqh_first;                   \
 622         struct type **swap_last = (head1)->tqh_last;                    \
 623         (head1)->tqh_first = (head2)->tqh_first;                        \
 624         (head1)->tqh_last = (head2)->tqh_last;                          \
 625         (head2)->tqh_first = swap_first;                                \
 626         (head2)->tqh_last = swap_last;                                  \
 627         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 628                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 629         else                                                            \
 630                 (head1)->tqh_last = &(head1)->tqh_first;                \
 631         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 632                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 633         else                                                            \
 634                 (head2)->tqh_last = &(head2)->tqh_first;                \
 635 } while (0)