sys/sys/queue.h

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  30  * $FreeBSD$
  31  */
  32
  33 #ifndef _SYS_QUEUE_H_
  34 #define _SYS_QUEUE_H_
  35
  36 #include <sys/cdefs.h>
  37
  38 /*
  39  * This file defines four types of data structures: singly-linked lists,
  40  * singly-linked tail queues, lists and tail queues.
  41  *
  42  * A singly-linked list is headed by a single forward pointer. The elements
  43  * are singly linked for minimum space and pointer manipulation overhead at
  44  * the expense of O(n) removal for arbitrary elements. New elements can be
  45  * added to the list after an existing element or at the head of the list.
  46  * Elements being removed from the head of the list should use the explicit
  47  * macro for this purpose for optimum efficiency. A singly-linked list may
  48  * only be traversed in the forward direction.  Singly-linked lists are ideal
  49  * for applications with large datasets and few or no removals or for
  50  * implementing a LIFO queue.
  51  *
  52  * A singly-linked tail queue is headed by a pair of pointers, one to the
  53  * head of the list and the other to the tail of the list. The elements are
  54  * singly linked for minimum space and pointer manipulation overhead at the
  55  * expense of O(n) removal for arbitrary elements. New elements can be added
  56  * to the list after an existing element, at the head of the list, or at the
  57  * end of the list. Elements being removed from the head of the tail queue
  58  * should use the explicit macro for this purpose for optimum efficiency.
  59  * A singly-linked tail queue may only be traversed in the forward direction.
  60  * Singly-linked tail queues are ideal for applications with large datasets
  61  * and few or no removals or for implementing a FIFO queue.
  62  *
  63  * A list is headed by a single forward pointer (or an array of forward
  64  * pointers for a hash table header). The elements are doubly linked
  65  * so that an arbitrary element can be removed without a need to
  66  * traverse the list. New elements can be added to the list before
  67  * or after an existing element or at the head of the list. A list
  68  * may be traversed in either 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  * _CLASS_HEAD                  +       +       +       +
  83  * _HEAD_INITIALIZER            +       +       +       +
  84  * _ENTRY                       +       +       +       +
  85  * _CLASS_ENTRY                 +       +       +       +
  86  * _INIT                        +       +       +       +
  87  * _EMPTY                       +       +       +       +
  88  * _FIRST                       +       +       +       +
  89  * _NEXT                        +       +       +       +
  90  * _PREV                        -       +       -       +
  91  * _LAST                        -       -       +       +
  92  * _FOREACH                     +       +       +       +
  93  * _FOREACH_FROM                +       +       +       +
  94  * _FOREACH_SAFE                +       +       +       +
  95  * _FOREACH_FROM_SAFE           +       +       +       +
  96  * _FOREACH_REVERSE             -       -       -       +
  97  * _FOREACH_REVERSE_FROM        -       -       -       +
  98  * _FOREACH_REVERSE_SAFE        -       -       -       +
  99  * _FOREACH_REVERSE_FROM_SAFE   -       -       -       +
 100  * _INSERT_HEAD                 +       +       +       +
 101  * _INSERT_BEFORE               -       +       -       +
 102  * _INSERT_AFTER                +       +       +       +
 103  * _INSERT_TAIL                 -       -       +       +
 104  * _CONCAT                      -       -       +       +
 105  * _REMOVE_AFTER                +       -       +       -
 106  * _REMOVE_HEAD                 +       -       +       -
 107  * _REMOVE                      +       +       +       +
 108  * _SWAP                        +       +       +       +
 109  *
 110  */
 111 #ifdef QUEUE_MACRO_DEBUG
 112 /* Store the last 2 places the queue element or head was altered */
 113 struct qm_trace {
 114         unsigned long    lastline;
 115         unsigned long    prevline;
 116         const char      *lastfile;
 117         const char      *prevfile;
 118 };
 119
 120 #define TRACEBUF        struct qm_trace trace;
 121 #define TRACEBUF_INITIALIZER    { __LINE__, 0, __FILE__, NULL } ,
 122 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 123 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 124
 125 #define QMD_TRACE_HEAD(head) do {                                       \
 126         (head)->trace.prevline = (head)->trace.lastline;                \
 127         (head)->trace.prevfile = (head)->trace.lastfile;                \
 128         (head)->trace.lastline = __LINE__;                              \
 129         (head)->trace.lastfile = __FILE__;                              \
 130 } while (0)
 131
 132 #define QMD_TRACE_ELEM(elem) do {                                       \
 133         (elem)->trace.prevline = (elem)->trace.lastline;                \
 134         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 135         (elem)->trace.lastline = __LINE__;                              \
 136         (elem)->trace.lastfile = __FILE__;                              \
 137 } while (0)
 138
 139 #else
 140 #define QMD_TRACE_ELEM(elem)
 141 #define QMD_TRACE_HEAD(head)
 142 #define QMD_SAVELINK(name, link)
 143 #define TRACEBUF
 144 #define TRACEBUF_INITIALIZER
 145 #define TRASHIT(x)
 146 #endif  /* QUEUE_MACRO_DEBUG */
 147
 148 #ifdef __cplusplus
 149 /*
 150  * In C++ there can be structure lists and class lists:
 151  */
 152 #define QUEUE_TYPEOF(type) type
 153 #else
 154 #define QUEUE_TYPEOF(type) struct type
 155 #endif
 156
 157 /*
 158  * Singly-linked List declarations.
 159  */
 160 #define SLIST_HEAD(name, type)                                          \
 161 struct name {                                                           \
 162         struct type *slh_first; /* first element */                     \
 163 }
 164
 165 #define SLIST_CLASS_HEAD(name, type)                                    \
 166 struct name {                                                           \
 167         class type *slh_first;  /* first element */                     \
 168 }
 169
 170 #define SLIST_HEAD_INITIALIZER(head)                                    \
 171         { NULL }
 172
 173 #define SLIST_ENTRY(type)                                               \
 174 struct {                                                                \
 175         struct type *sle_next;  /* next element */                      \
 176 }
 177
 178 #define SLIST_CLASS_ENTRY(type)                                         \
 179 struct {                                                                \
 180         class type *sle_next;           /* next element */              \
 181 }
 182
 183 /*
 184  * Singly-linked List functions.
 185  */
 186 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 187
 188 #define SLIST_FIRST(head)       ((head)->slh_first)
 189
 190 #define SLIST_FOREACH(var, head, field)                                 \
 191         for ((var) = SLIST_FIRST((head));                               \
 192             (var);                                                      \
 193             (var) = SLIST_NEXT((var), field))
 194
 195 #define SLIST_FOREACH_FROM(var, head, field)                            \
 196         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 197             (var);                                                      \
 198             (var) = SLIST_NEXT((var), field))
 199
 200 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 201         for ((var) = SLIST_FIRST((head));                               \
 202             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 203             (var) = (tvar))
 204
 205 #define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 206         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 207             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 208             (var) = (tvar))
 209
 210 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 211         for ((varp) = &SLIST_FIRST((head));                             \
 212             ((var) = *(varp)) != NULL;                                  \
 213             (varp) = &SLIST_NEXT((var), field))
 214
 215 #define SLIST_INIT(head) do {                                           \
 216         SLIST_FIRST((head)) = NULL;                                     \
 217 } while (0)
 218
 219 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 220         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 221         SLIST_NEXT((slistelm), field) = (elm);                          \
 222 } while (0)
 223
 224 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 225         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 226         SLIST_FIRST((head)) = (elm);                                    \
 227 } while (0)
 228
 229 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 230
 231 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 232         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 233         if (SLIST_FIRST((head)) == (elm)) {                             \
 234                 SLIST_REMOVE_HEAD((head), field);                       \
 235         }                                                               \
 236         else {                                                          \
 237                 QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head);         \
 238                 while (SLIST_NEXT(curelm, field) != (elm))              \
 239                         curelm = SLIST_NEXT(curelm, field);             \
 240                 SLIST_REMOVE_AFTER(curelm, field);                      \
 241         }                                                               \
 242         TRASHIT(*oldnext);                                              \
 243 } while (0)
 244
 245 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 246         SLIST_NEXT(elm, field) =                                        \
 247             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 248 } while (0)
 249
 250 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 251         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 252 } while (0)
 253
 254 #define SLIST_SWAP(head1, head2, type) do {                             \
 255         QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
 256         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
 257         SLIST_FIRST(head2) = swap_first;                                \
 258 } while (0)
 259
 260 /*
 261  * Singly-linked Tail queue declarations.
 262  */
 263 #define STAILQ_HEAD(name, type)                                         \
 264 struct name {                                                           \
 265         struct type *stqh_first;/* first element */                     \
 266         struct type **stqh_last;/* addr of last next element */         \
 267 }
 268
 269 #define STAILQ_CLASS_HEAD(name, type)                                   \
 270 struct name {                                                           \
 271         class type *stqh_first; /* first element */                     \
 272         class type **stqh_last; /* addr of last next element */         \
 273 }
 274
 275 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 276         { NULL, &(head).stqh_first }
 277
 278 #define STAILQ_ENTRY(type)                                              \
 279 struct {                                                                \
 280         struct type *stqe_next; /* next element */                      \
 281 }
 282
 283 #define STAILQ_CLASS_ENTRY(type)                                        \
 284 struct {                                                                \
 285         class type *stqe_next;  /* next element */                      \
 286 }
 287
 288 /*
 289  * Singly-linked Tail queue functions.
 290  */
 291 #define STAILQ_CONCAT(head1, head2) do {                                \
 292         if (!STAILQ_EMPTY((head2))) {                                   \
 293                 *(head1)->stqh_last = (head2)->stqh_first;              \
 294                 (head1)->stqh_last = (head2)->stqh_last;                \
 295                 STAILQ_INIT((head2));                                   \
 296         }                                                               \
 297 } while (0)
 298
 299 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 300
 301 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 302
 303 #define STAILQ_FOREACH(var, head, field)                                \
 304         for((var) = STAILQ_FIRST((head));                               \
 305            (var);                                                       \
 306            (var) = STAILQ_NEXT((var), field))
 307
 308 #define STAILQ_FOREACH_FROM(var, head, field)                           \
 309         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 310            (var);                                                       \
 311            (var) = STAILQ_NEXT((var), field))
 312
 313 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 314         for ((var) = STAILQ_FIRST((head));                              \
 315             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 316             (var) = (tvar))
 317
 318 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
 319         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 320             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 321             (var) = (tvar))
 322
 323 #define STAILQ_INIT(head) do {                                          \
 324         STAILQ_FIRST((head)) = NULL;                                    \
 325         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 326 } while (0)
 327
 328 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 329         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 330                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 331         STAILQ_NEXT((tqelm), field) = (elm);                            \
 332 } while (0)
 333
 334 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 335         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 336                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 337         STAILQ_FIRST((head)) = (elm);                                   \
 338 } while (0)
 339
 340 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 341         STAILQ_NEXT((elm), field) = NULL;                               \
 342         *(head)->stqh_last = (elm);                                     \
 343         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 344 } while (0)
 345
 346 #define STAILQ_LAST(head, type, field)                          \
 347         (STAILQ_EMPTY((head)) ? NULL :                          \
 348             __containerof((head)->stqh_last,                    \
 349             QUEUE_TYPEOF(type), field.stqe_next))
 350
 351 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 352
 353 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 354         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 355         if (STAILQ_FIRST((head)) == (elm)) {                            \
 356                 STAILQ_REMOVE_HEAD((head), field);                      \
 357         }                                                               \
 358         else {                                                          \
 359                 QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
 360                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 361                         curelm = STAILQ_NEXT(curelm, field);            \
 362                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 363         }                                                               \
 364         TRASHIT(*oldnext);                                              \
 365 } while (0)
 366
 367 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 368         if ((STAILQ_NEXT(elm, field) =                                  \
 369              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 370                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 371 } while (0)
 372
 373 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 374         if ((STAILQ_FIRST((head)) =                                     \
 375              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 376                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 377 } while (0)
 378
 379 #define STAILQ_SWAP(head1, head2, type) do {                            \
 380         QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
 381         QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
 382         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 383         (head1)->stqh_last = (head2)->stqh_last;                        \
 384         STAILQ_FIRST(head2) = swap_first;                               \
 385         (head2)->stqh_last = swap_last;                                 \
 386         if (STAILQ_EMPTY(head1))                                        \
 387                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 388         if (STAILQ_EMPTY(head2))                                        \
 389                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 390 } while (0)
 391
 392
 393 /*
 394  * List declarations.
 395  */
 396 #define LIST_HEAD(name, type)                                           \
 397 struct name {                                                           \
 398         struct type *lh_first;  /* first element */                     \
 399 }
 400
 401 #define LIST_CLASS_HEAD(name, type)                                     \
 402 struct name {                                                           \
 403         class type *lh_first;   /* first element */                     \
 404 }
 405
 406 #define LIST_HEAD_INITIALIZER(head)                                     \
 407         { NULL }
 408
 409 #define LIST_ENTRY(type)                                                \
 410 struct {                                                                \
 411         struct type *le_next;   /* next element */                      \
 412         struct type **le_prev;  /* address of previous next element */  \
 413 }
 414
 415 #define LIST_CLASS_ENTRY(type)                                          \
 416 struct {                                                                \
 417         class type *le_next;    /* next element */                      \
 418         class type **le_prev;   /* address of previous next element */  \
 419 }
 420
 421 /*
 422  * List functions.
 423  */
 424
 425 #if (defined(_KERNEL) && defined(INVARIANTS))
 426 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 427         if (LIST_FIRST((head)) != NULL &&                               \
 428             LIST_FIRST((head))->field.le_prev !=                        \
 429              &LIST_FIRST((head)))                                       \
 430                 panic("Bad list head %p first->prev != head", (head));  \
 431 } while (0)
 432
 433 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 434         if (LIST_NEXT((elm), field) != NULL &&                          \
 435             LIST_NEXT((elm), field)->field.le_prev !=                   \
 436              &((elm)->field.le_next))                                   \
 437                 panic("Bad link elm %p next->prev != elm", (elm));      \
 438 } while (0)
 439
 440 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 441         if (*(elm)->field.le_prev != (elm))                             \
 442                 panic("Bad link elm %p prev->next != elm", (elm));      \
 443 } while (0)
 444 #else
 445 #define QMD_LIST_CHECK_HEAD(head, field)
 446 #define QMD_LIST_CHECK_NEXT(elm, field)
 447 #define QMD_LIST_CHECK_PREV(elm, field)
 448 #endif /* (_KERNEL && INVARIANTS) */
 449
 450 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 451
 452 #define LIST_FIRST(head)        ((head)->lh_first)
 453
 454 #define LIST_FOREACH(var, head, field)                                  \
 455         for ((var) = LIST_FIRST((head));                                \
 456             (var);                                                      \
 457             (var) = LIST_NEXT((var), field))
 458
 459 #define LIST_FOREACH_FROM(var, head, field)                             \
 460         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 461             (var);                                                      \
 462             (var) = LIST_NEXT((var), field))
 463
 464 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 465         for ((var) = LIST_FIRST((head));                                \
 466             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 467             (var) = (tvar))
 468
 469 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
 470         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 471             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 472             (var) = (tvar))
 473
 474 #define LIST_INIT(head) do {                                            \
 475         LIST_FIRST((head)) = NULL;                                      \
 476 } while (0)
 477
 478 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 479         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 480         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 481                 LIST_NEXT((listelm), field)->field.le_prev =            \
 482                     &LIST_NEXT((elm), field);                           \
 483         LIST_NEXT((listelm), field) = (elm);                            \
 484         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 485 } while (0)
 486
 487 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 488         QMD_LIST_CHECK_PREV(listelm, field);                            \
 489         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 490         LIST_NEXT((elm), field) = (listelm);                            \
 491         *(listelm)->field.le_prev = (elm);                              \
 492         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 493 } while (0)
 494
 495 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 496         QMD_LIST_CHECK_HEAD((head), field);                             \
 497         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 498                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 499         LIST_FIRST((head)) = (elm);                                     \
 500         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 501 } while (0)
 502
 503 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 504
 505 #define LIST_PREV(elm, head, type, field)                       \
 506         ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
 507             __containerof((elm)->field.le_prev,                 \
 508             QUEUE_TYPEOF(type), field.le_next))
 509
 510 #define LIST_REMOVE(elm, field) do {                                    \
 511         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 512         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 513         QMD_LIST_CHECK_NEXT(elm, field);                                \
 514         QMD_LIST_CHECK_PREV(elm, field);                                \
 515         if (LIST_NEXT((elm), field) != NULL)                            \
 516                 LIST_NEXT((elm), field)->field.le_prev =                \
 517                     (elm)->field.le_prev;                               \
 518         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 519         TRASHIT(*oldnext);                                              \
 520         TRASHIT(*oldprev);                                              \
 521 } while (0)
 522
 523 #define LIST_SWAP(head1, head2, type, field) do {                       \
 524         QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
 525         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 526         LIST_FIRST((head2)) = swap_tmp;                                 \
 527         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 528                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 529         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 530                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 531 } while (0)
 532
 533 /*
 534  * Tail queue declarations.
 535  */
 536 #define TAILQ_HEAD(name, type)                                          \
 537 struct name {                                                           \
 538         struct type *tqh_first; /* first element */                     \
 539         struct type **tqh_last; /* addr of last next element */         \
 540         TRACEBUF                                                        \
 541 }
 542
 543 #define TAILQ_CLASS_HEAD(name, type)                                    \
 544 struct name {                                                           \
 545         class type *tqh_first;  /* first element */                     \
 546         class type **tqh_last;  /* addr of last next element */         \
 547         TRACEBUF                                                        \
 548 }
 549
 550 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 551         { NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }
 552
 553 #define TAILQ_ENTRY(type)                                               \
 554 struct {                                                                \
 555         struct type *tqe_next;  /* next element */                      \
 556         struct type **tqe_prev; /* address of previous next element */  \
 557         TRACEBUF                                                        \
 558 }
 559
 560 #define TAILQ_CLASS_ENTRY(type)                                         \
 561 struct {                                                                \
 562         class type *tqe_next;   /* next element */                      \
 563         class type **tqe_prev;  /* address of previous next element */  \
 564         TRACEBUF                                                        \
 565 }
 566
 567 /*
 568  * Tail queue functions.
 569  */
 570 #if (defined(_KERNEL) && defined(INVARIANTS))
 571 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 572         if (!TAILQ_EMPTY(head) &&                                       \
 573             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 574              &TAILQ_FIRST((head)))                                      \
 575                 panic("Bad tailq head %p first->prev != head", (head)); \
 576 } while (0)
 577
 578 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 579         if (*(head)->tqh_last != NULL)                                  \
 580                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 581 } while (0)
 582
 583 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 584         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 585             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 586              &((elm)->field.tqe_next))                                  \
 587                 panic("Bad link elm %p next->prev != elm", (elm));      \
 588 } while (0)
 589
 590 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 591         if (*(elm)->field.tqe_prev != (elm))                            \
 592                 panic("Bad link elm %p prev->next != elm", (elm));      \
 593 } while (0)
 594 #else
 595 #define QMD_TAILQ_CHECK_HEAD(head, field)
 596 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 597 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 598 #define QMD_TAILQ_CHECK_PREV(elm, field)
 599 #endif /* (_KERNEL && INVARIANTS) */
 600
 601 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 602         if (!TAILQ_EMPTY(head2)) {                                      \
 603                 *(head1)->tqh_last = (head2)->tqh_first;                \
 604                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 605                 (head1)->tqh_last = (head2)->tqh_last;                  \
 606                 TAILQ_INIT((head2));                                    \
 607                 QMD_TRACE_HEAD(head1);                                  \
 608                 QMD_TRACE_HEAD(head2);                                  \
 609         }                                                               \
 610 } while (0)
 611
 612 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 613
 614 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 615
 616 #define TAILQ_FOREACH(var, head, field)                                 \
 617         for ((var) = TAILQ_FIRST((head));                               \
 618             (var);                                                      \
 619             (var) = TAILQ_NEXT((var), field))
 620
 621 #define TAILQ_FOREACH_FROM(var, head, field)                            \
 622         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 623             (var);                                                      \
 624             (var) = TAILQ_NEXT((var), field))
 625
 626 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 627         for ((var) = TAILQ_FIRST((head));                               \
 628             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 629             (var) = (tvar))
 630
 631 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 632         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 633             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 634             (var) = (tvar))
 635
 636 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 637         for ((var) = TAILQ_LAST((head), headname);                      \
 638             (var);                                                      \
 639             (var) = TAILQ_PREV((var), headname, field))
 640
 641 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)          \
 642         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 643             (var);                                                      \
 644             (var) = TAILQ_PREV((var), headname, field))
 645
 646 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 647         for ((var) = TAILQ_LAST((head), headname);                      \
 648             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 649             (var) = (tvar))
 650
 651 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
 652         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 653             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 654             (var) = (tvar))
 655
 656 #define TAILQ_INIT(head) do {                                           \
 657         TAILQ_FIRST((head)) = NULL;                                     \
 658         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 659         QMD_TRACE_HEAD(head);                                           \
 660 } while (0)
 661
 662 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 663         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 664         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 665                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 666                     &TAILQ_NEXT((elm), field);                          \
 667         else {                                                          \
 668                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 669                 QMD_TRACE_HEAD(head);                                   \
 670         }                                                               \
 671         TAILQ_NEXT((listelm), field) = (elm);                           \
 672         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 673         QMD_TRACE_ELEM(&(elm)->field);                                  \
 674         QMD_TRACE_ELEM(&(listelm)->field);                              \
 675 } while (0)
 676
 677 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 678         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 679         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 680         TAILQ_NEXT((elm), field) = (listelm);                           \
 681         *(listelm)->field.tqe_prev = (elm);                             \
 682         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 683         QMD_TRACE_ELEM(&(elm)->field);                                  \
 684         QMD_TRACE_ELEM(&(listelm)->field);                              \
 685 } while (0)
 686
 687 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 688         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 689         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 690                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 691                     &TAILQ_NEXT((elm), field);                          \
 692         else                                                            \
 693                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 694         TAILQ_FIRST((head)) = (elm);                                    \
 695         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 696         QMD_TRACE_HEAD(head);                                           \
 697         QMD_TRACE_ELEM(&(elm)->field);                                  \
 698 } while (0)
 699
 700 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 701         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 702         TAILQ_NEXT((elm), field) = NULL;                                \
 703         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 704         *(head)->tqh_last = (elm);                                      \
 705         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 706         QMD_TRACE_HEAD(head);                                           \
 707         QMD_TRACE_ELEM(&(elm)->field);                                  \
 708 } while (0)
 709
 710 #define TAILQ_LAST(head, headname)                                      \
 711         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 712
 713 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 714
 715 #define TAILQ_PREV(elm, headname, field)                                \
 716         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 717
 718 #define TAILQ_REMOVE(head, elm, field) do {                             \
 719         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 720         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 721         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 722         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 723         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 724                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 725                     (elm)->field.tqe_prev;                              \
 726         else {                                                          \
 727                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 728                 QMD_TRACE_HEAD(head);                                   \
 729         }                                                               \
 730         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 731         TRASHIT(*oldnext);                                              \
 732         TRASHIT(*oldprev);                                              \
 733         QMD_TRACE_ELEM(&(elm)->field);                                  \
 734 } while (0)
 735
 736 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 737         QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
 738         QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
 739         (head1)->tqh_first = (head2)->tqh_first;                        \
 740         (head1)->tqh_last = (head2)->tqh_last;                          \
 741         (head2)->tqh_first = swap_first;                                \
 742         (head2)->tqh_last = swap_last;                                  \
 743         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 744                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 745         else                                                            \
 746                 (head1)->tqh_last = &(head1)->tqh_first;                \
 747         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 748                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 749         else                                                            \
 750                 (head2)->tqh_last = &(head2)->tqh_first;                \
 751 } while (0)
 752
 753 #endif /* !_SYS_QUEUE_H_ */