akaros/kern/include/sys/queue.h
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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 * $FreeBSD$
  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 */
 108struct 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)                                          \
 145struct name {                                                           \
 146        struct type *slh_first; /* first element */                     \
 147}
 148
 149#define SLIST_HEAD_INITIALIZER(head)                                    \
 150        { NULL }
 151
 152#define SLIST_ENTRY(type)                                               \
 153struct {                                                                \
 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)                                         \
 222struct 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)                                              \
 231struct {                                                                \
 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)                                               \
 336struct 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)                                            \
 344struct {                                                                \
 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)                                          \
 455struct 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)                                               \
 465struct {                                                                \
 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)
 636