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  * Below is a summary of implemented functions where:
  80  *  +  means the macro is available
  81  *  -  means the macro is not available
  82  *  s  means the macro is available but is slow (runs in O(n) time)
  83  *
  84  *                              SLIST   LIST    STAILQ  TAILQ
  85  * _HEAD                        +       +       +       +
  86  * _CLASS_HEAD                  +       +       +       +
  87  * _HEAD_INITIALIZER            +       +       +       +
  88  * _ENTRY                       +       +       +       +
  89  * _CLASS_ENTRY                 +       +       +       +
  90  * _INIT                        +       +       +       +
  91  * _EMPTY                       +       +       +       +
  92  * _FIRST                       +       +       +       +
  93  * _NEXT                        +       +       +       +
  94  * _PREV                        -       +       -       +
  95  * _LAST                        -       -       +       +
  96  * _FOREACH                     +       +       +       +
  97  * _FOREACH_FROM                +       +       +       +
  98  * _FOREACH_SAFE                +       +       +       +
  99  * _FOREACH_FROM_SAFE           +       +       +       +
 100  * _FOREACH_REVERSE             -       -       -       +
 101  * _FOREACH_REVERSE_FROM        -       -       -       +
 102  * _FOREACH_REVERSE_SAFE        -       -       -       +
 103  * _FOREACH_REVERSE_FROM_SAFE   -       -       -       +
 104  * _INSERT_HEAD                 +       +       +       +
 105  * _INSERT_BEFORE               -       +       -       +
 106  * _INSERT_AFTER                +       +       +       +
 107  * _INSERT_TAIL                 -       -       +       +
 108  * _CONCAT                      s       s       +       +
 109  * _REMOVE_AFTER                +       -       +       -
 110  * _REMOVE_HEAD                 +       -       +       -
 111  * _REMOVE                      s       +       s       +
 112  * _SWAP                        +       +       +       +
 113  *
 114  */
 115 #ifdef QUEUE_MACRO_DEBUG
 116 /* Store the last 2 places the queue element or head was altered */
 117 struct qm_trace {
 118         unsigned long    lastline;
 119         unsigned long    prevline;
 120         const char      *lastfile;
 121         const char      *prevfile;
 122 };
 123
 124 #define TRACEBUF        struct qm_trace trace;
 125 #define TRACEBUF_INITIALIZER    { __LINE__, 0, __FILE__, NULL } ,
 126 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 127 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 128
 129 #define QMD_TRACE_HEAD(head) do {                                       \
 130         (head)->trace.prevline = (head)->trace.lastline;                \
 131         (head)->trace.prevfile = (head)->trace.lastfile;                \
 132         (head)->trace.lastline = __LINE__;                              \
 133         (head)->trace.lastfile = __FILE__;                              \
 134 } while (0)
 135
 136 #define QMD_TRACE_ELEM(elem) do {                                       \
 137         (elem)->trace.prevline = (elem)->trace.lastline;                \
 138         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 139         (elem)->trace.lastline = __LINE__;                              \
 140         (elem)->trace.lastfile = __FILE__;                              \
 141 } while (0)
 142
 143 #else
 144 #define QMD_TRACE_ELEM(elem)
 145 #define QMD_TRACE_HEAD(head)
 146 #define QMD_SAVELINK(name, link)
 147 #define TRACEBUF
 148 #define TRACEBUF_INITIALIZER
 149 #define TRASHIT(x)
 150 #endif  /* QUEUE_MACRO_DEBUG */
 151
 152 #ifdef __cplusplus
 153 /*
 154  * In C++ there can be structure lists and class lists:
 155  */
 156 #define QUEUE_TYPEOF(type) type
 157 #else
 158 #define QUEUE_TYPEOF(type) struct type
 159 #endif
 160
 161 /*
 162  * Singly-linked List declarations.
 163  */
 164 #define SLIST_HEAD(name, type)                                          \
 165 struct name {                                                           \
 166         struct type *slh_first; /* first element */                     \
 167 }
 168
 169 #define SLIST_CLASS_HEAD(name, type)                                    \
 170 struct name {                                                           \
 171         class type *slh_first;  /* first element */                     \
 172 }
 173
 174 #define SLIST_HEAD_INITIALIZER(head)                                    \
 175         { NULL }
 176
 177 #define SLIST_ENTRY(type)                                               \
 178 struct {                                                                \
 179         struct type *sle_next;  /* next element */                      \
 180 }
 181
 182 #define SLIST_CLASS_ENTRY(type)                                         \
 183 struct {                                                                \
 184         class type *sle_next;           /* next element */              \
 185 }
 186
 187 /*
 188  * Singly-linked List functions.
 189  */
 190 #define SLIST_CONCAT(head1, head2, type, field) do {                    \
 191         QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head1);                \
 192         if (curelm == NULL) {                                           \
 193                 if ((SLIST_FIRST(head1) = SLIST_FIRST(head2)) != NULL)  \
 194                         SLIST_INIT(head2);                              \
 195         } else if (SLIST_FIRST(head2) != NULL) {                        \
 196                 while (SLIST_NEXT(curelm, field) != NULL)               \
 197                         curelm = SLIST_NEXT(curelm, field);             \
 198                 SLIST_NEXT(curelm, field) = SLIST_FIRST(head2);         \
 199                 SLIST_INIT(head2);                                      \
 200         }                                                               \
 201 } while (0)
 202
 203 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 204
 205 #define SLIST_FIRST(head)       ((head)->slh_first)
 206
 207 #define SLIST_FOREACH(var, head, field)                                 \
 208         for ((var) = SLIST_FIRST((head));                               \
 209             (var);                                                      \
 210             (var) = SLIST_NEXT((var), field))
 211
 212 #define SLIST_FOREACH_FROM(var, head, field)                            \
 213         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 214             (var);                                                      \
 215             (var) = SLIST_NEXT((var), field))
 216
 217 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 218         for ((var) = SLIST_FIRST((head));                               \
 219             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 220             (var) = (tvar))
 221
 222 #define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 223         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 224             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 225             (var) = (tvar))
 226
 227 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 228         for ((varp) = &SLIST_FIRST((head));                             \
 229             ((var) = *(varp)) != NULL;                                  \
 230             (varp) = &SLIST_NEXT((var), field))
 231
 232 #define SLIST_INIT(head) do {                                           \
 233         SLIST_FIRST((head)) = NULL;                                     \
 234 } while (0)
 235
 236 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 237         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 238         SLIST_NEXT((slistelm), field) = (elm);                          \
 239 } while (0)
 240
 241 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 242         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 243         SLIST_FIRST((head)) = (elm);                                    \
 244 } while (0)
 245
 246 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 247
 248 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 249         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 250         if (SLIST_FIRST((head)) == (elm)) {                             \
 251                 SLIST_REMOVE_HEAD((head), field);                       \
 252         }                                                               \
 253         else {                                                          \
 254                 QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head);         \
 255                 while (SLIST_NEXT(curelm, field) != (elm))              \
 256                         curelm = SLIST_NEXT(curelm, field);             \
 257                 SLIST_REMOVE_AFTER(curelm, field);                      \
 258         }                                                               \
 259         TRASHIT(*oldnext);                                              \
 260 } while (0)
 261
 262 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 263         SLIST_NEXT(elm, field) =                                        \
 264             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 265 } while (0)
 266
 267 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 268         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 269 } while (0)
 270
 271 #define SLIST_SWAP(head1, head2, type) do {                             \
 272         QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
 273         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
 274         SLIST_FIRST(head2) = swap_first;                                \
 275 } while (0)
 276
 277 /*
 278  * Singly-linked Tail queue declarations.
 279  */
 280 #define STAILQ_HEAD(name, type)                                         \
 281 struct name {                                                           \
 282         struct type *stqh_first;/* first element */                     \
 283         struct type **stqh_last;/* addr of last next element */         \
 284 }
 285
 286 #define STAILQ_CLASS_HEAD(name, type)                                   \
 287 struct name {                                                           \
 288         class type *stqh_first; /* first element */                     \
 289         class type **stqh_last; /* addr of last next element */         \
 290 }
 291
 292 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 293         { NULL, &(head).stqh_first }
 294
 295 #define STAILQ_ENTRY(type)                                              \
 296 struct {                                                                \
 297         struct type *stqe_next; /* next element */                      \
 298 }
 299
 300 #define STAILQ_CLASS_ENTRY(type)                                        \
 301 struct {                                                                \
 302         class type *stqe_next;  /* next element */                      \
 303 }
 304
 305 /*
 306  * Singly-linked Tail queue functions.
 307  */
 308 #define STAILQ_CONCAT(head1, head2) do {                                \
 309         if (!STAILQ_EMPTY((head2))) {                                   \
 310                 *(head1)->stqh_last = (head2)->stqh_first;              \
 311                 (head1)->stqh_last = (head2)->stqh_last;                \
 312                 STAILQ_INIT((head2));                                   \
 313         }                                                               \
 314 } while (0)
 315
 316 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 317
 318 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 319
 320 #define STAILQ_FOREACH(var, head, field)                                \
 321         for((var) = STAILQ_FIRST((head));                               \
 322            (var);                                                       \
 323            (var) = STAILQ_NEXT((var), field))
 324
 325 #define STAILQ_FOREACH_FROM(var, head, field)                           \
 326         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 327            (var);                                                       \
 328            (var) = STAILQ_NEXT((var), field))
 329
 330 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 331         for ((var) = STAILQ_FIRST((head));                              \
 332             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 333             (var) = (tvar))
 334
 335 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
 336         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 337             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 338             (var) = (tvar))
 339
 340 #define STAILQ_INIT(head) do {                                          \
 341         STAILQ_FIRST((head)) = NULL;                                    \
 342         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 343 } while (0)
 344
 345 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 346         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 347                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 348         STAILQ_NEXT((tqelm), field) = (elm);                            \
 349 } while (0)
 350
 351 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 352         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 353                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 354         STAILQ_FIRST((head)) = (elm);                                   \
 355 } while (0)
 356
 357 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 358         STAILQ_NEXT((elm), field) = NULL;                               \
 359         *(head)->stqh_last = (elm);                                     \
 360         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 361 } while (0)
 362
 363 #define STAILQ_LAST(head, type, field)                          \
 364         (STAILQ_EMPTY((head)) ? NULL :                          \
 365             __containerof((head)->stqh_last,                    \
 366             QUEUE_TYPEOF(type), field.stqe_next))
 367
 368 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 369
 370 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 371         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 372         if (STAILQ_FIRST((head)) == (elm)) {                            \
 373                 STAILQ_REMOVE_HEAD((head), field);                      \
 374         }                                                               \
 375         else {                                                          \
 376                 QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
 377                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 378                         curelm = STAILQ_NEXT(curelm, field);            \
 379                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 380         }                                                               \
 381         TRASHIT(*oldnext);                                              \
 382 } while (0)
 383
 384 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 385         if ((STAILQ_NEXT(elm, field) =                                  \
 386              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 387                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 388 } while (0)
 389
 390 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 391         if ((STAILQ_FIRST((head)) =                                     \
 392              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 393                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 394 } while (0)
 395
 396 #define STAILQ_SWAP(head1, head2, type) do {                            \
 397         QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
 398         QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
 399         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 400         (head1)->stqh_last = (head2)->stqh_last;                        \
 401         STAILQ_FIRST(head2) = swap_first;                               \
 402         (head2)->stqh_last = swap_last;                                 \
 403         if (STAILQ_EMPTY(head1))                                        \
 404                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 405         if (STAILQ_EMPTY(head2))                                        \
 406                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 407 } while (0)
 408
 409
 410 /*
 411  * List declarations.
 412  */
 413 #define LIST_HEAD(name, type)                                           \
 414 struct name {                                                           \
 415         struct type *lh_first;  /* first element */                     \
 416 }
 417
 418 #define LIST_CLASS_HEAD(name, type)                                     \
 419 struct name {                                                           \
 420         class type *lh_first;   /* first element */                     \
 421 }
 422
 423 #define LIST_HEAD_INITIALIZER(head)                                     \
 424         { NULL }
 425
 426 #define LIST_ENTRY(type)                                                \
 427 struct {                                                                \
 428         struct type *le_next;   /* next element */                      \
 429         struct type **le_prev;  /* address of previous next element */  \
 430 }
 431
 432 #define LIST_CLASS_ENTRY(type)                                          \
 433 struct {                                                                \
 434         class type *le_next;    /* next element */                      \
 435         class type **le_prev;   /* address of previous next element */  \
 436 }
 437
 438 /*
 439  * List functions.
 440  */
 441
 442 #if (defined(_KERNEL) && defined(INVARIANTS))
 443 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 444         if (LIST_FIRST((head)) != NULL &&                               \
 445             LIST_FIRST((head))->field.le_prev !=                        \
 446              &LIST_FIRST((head)))                                       \
 447                 panic("Bad list head %p first->prev != head", (head));  \
 448 } while (0)
 449
 450 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 451         if (LIST_NEXT((elm), field) != NULL &&                          \
 452             LIST_NEXT((elm), field)->field.le_prev !=                   \
 453              &((elm)->field.le_next))                                   \
 454                 panic("Bad link elm %p next->prev != elm", (elm));      \
 455 } while (0)
 456
 457 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 458         if (*(elm)->field.le_prev != (elm))                             \
 459                 panic("Bad link elm %p prev->next != elm", (elm));      \
 460 } while (0)
 461 #else
 462 #define QMD_LIST_CHECK_HEAD(head, field)
 463 #define QMD_LIST_CHECK_NEXT(elm, field)
 464 #define QMD_LIST_CHECK_PREV(elm, field)
 465 #endif /* (_KERNEL && INVARIANTS) */
 466
 467 #define LIST_CONCAT(head1, head2, type, field) do {                           \
 468         QUEUE_TYPEOF(type) *curelm = LIST_FIRST(head1);                       \
 469         if (curelm == NULL) {                                                 \
 470                 if ((LIST_FIRST(head1) = LIST_FIRST(head2)) != NULL) {        \
 471                         LIST_FIRST(head2)->field.le_prev =                    \
 472                             &LIST_FIRST((head1));                             \
 473                         LIST_INIT(head2);                                     \
 474                 }                                                             \
 475         } else if (LIST_FIRST(head2) != NULL) {                               \
 476                 while (LIST_NEXT(curelm, field) != NULL)                      \
 477                         curelm = LIST_NEXT(curelm, field);                    \
 478                 LIST_NEXT(curelm, field) = LIST_FIRST(head2);                 \
 479                 LIST_FIRST(head2)->field.le_prev = &LIST_NEXT(curelm, field); \
 480                 LIST_INIT(head2);                                             \
 481         }                                                                     \
 482 } while (0)
 483
 484 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 485
 486 #define LIST_FIRST(head)        ((head)->lh_first)
 487
 488 #define LIST_FOREACH(var, head, field)                                  \
 489         for ((var) = LIST_FIRST((head));                                \
 490             (var);                                                      \
 491             (var) = LIST_NEXT((var), field))
 492
 493 #define LIST_FOREACH_FROM(var, head, field)                             \
 494         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 495             (var);                                                      \
 496             (var) = LIST_NEXT((var), field))
 497
 498 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 499         for ((var) = LIST_FIRST((head));                                \
 500             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 501             (var) = (tvar))
 502
 503 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
 504         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 505             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 506             (var) = (tvar))
 507
 508 #define LIST_INIT(head) do {                                            \
 509         LIST_FIRST((head)) = NULL;                                      \
 510 } while (0)
 511
 512 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 513         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 514         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 515                 LIST_NEXT((listelm), field)->field.le_prev =            \
 516                     &LIST_NEXT((elm), field);                           \
 517         LIST_NEXT((listelm), field) = (elm);                            \
 518         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 519 } while (0)
 520
 521 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 522         QMD_LIST_CHECK_PREV(listelm, field);                            \
 523         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 524         LIST_NEXT((elm), field) = (listelm);                            \
 525         *(listelm)->field.le_prev = (elm);                              \
 526         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 527 } while (0)
 528
 529 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 530         QMD_LIST_CHECK_HEAD((head), field);                             \
 531         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 532                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 533         LIST_FIRST((head)) = (elm);                                     \
 534         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 535 } while (0)
 536
 537 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 538
 539 #define LIST_PREV(elm, head, type, field)                       \
 540         ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
 541             __containerof((elm)->field.le_prev,                 \
 542             QUEUE_TYPEOF(type), field.le_next))
 543
 544 #define LIST_REMOVE(elm, field) do {                                    \
 545         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 546         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 547         QMD_LIST_CHECK_NEXT(elm, field);                                \
 548         QMD_LIST_CHECK_PREV(elm, field);                                \
 549         if (LIST_NEXT((elm), field) != NULL)                            \
 550                 LIST_NEXT((elm), field)->field.le_prev =                \
 551                     (elm)->field.le_prev;                               \
 552         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 553         TRASHIT(*oldnext);                                              \
 554         TRASHIT(*oldprev);                                              \
 555 } while (0)
 556
 557 #define LIST_SWAP(head1, head2, type, field) do {                       \
 558         QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
 559         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 560         LIST_FIRST((head2)) = swap_tmp;                                 \
 561         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 562                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 563         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 564                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 565 } while (0)
 566
 567 /*
 568  * Tail queue declarations.
 569  */
 570 #define TAILQ_HEAD(name, type)                                          \
 571 struct name {                                                           \
 572         struct type *tqh_first; /* first element */                     \
 573         struct type **tqh_last; /* addr of last next element */         \
 574         TRACEBUF                                                        \
 575 }
 576
 577 #define TAILQ_CLASS_HEAD(name, type)                                    \
 578 struct name {                                                           \
 579         class type *tqh_first;  /* first element */                     \
 580         class type **tqh_last;  /* addr of last next element */         \
 581         TRACEBUF                                                        \
 582 }
 583
 584 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 585         { NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }
 586
 587 #define TAILQ_ENTRY(type)                                               \
 588 struct {                                                                \
 589         struct type *tqe_next;  /* next element */                      \
 590         struct type **tqe_prev; /* address of previous next element */  \
 591         TRACEBUF                                                        \
 592 }
 593
 594 #define TAILQ_CLASS_ENTRY(type)                                         \
 595 struct {                                                                \
 596         class type *tqe_next;   /* next element */                      \
 597         class type **tqe_prev;  /* address of previous next element */  \
 598         TRACEBUF                                                        \
 599 }
 600
 601 /*
 602  * Tail queue functions.
 603  */
 604 #if (defined(_KERNEL) && defined(INVARIANTS))
 605 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 606         if (!TAILQ_EMPTY(head) &&                                       \
 607             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 608              &TAILQ_FIRST((head)))                                      \
 609                 panic("Bad tailq head %p first->prev != head", (head)); \
 610 } while (0)
 611
 612 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 613         if (*(head)->tqh_last != NULL)                                  \
 614                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 615 } while (0)
 616
 617 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 618         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 619             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 620              &((elm)->field.tqe_next))                                  \
 621                 panic("Bad link elm %p next->prev != elm", (elm));      \
 622 } while (0)
 623
 624 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 625         if (*(elm)->field.tqe_prev != (elm))                            \
 626                 panic("Bad link elm %p prev->next != elm", (elm));      \
 627 } while (0)
 628 #else
 629 #define QMD_TAILQ_CHECK_HEAD(head, field)
 630 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 631 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 632 #define QMD_TAILQ_CHECK_PREV(elm, field)
 633 #endif /* (_KERNEL && INVARIANTS) */
 634
 635 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 636         if (!TAILQ_EMPTY(head2)) {                                      \
 637                 *(head1)->tqh_last = (head2)->tqh_first;                \
 638                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 639                 (head1)->tqh_last = (head2)->tqh_last;                  \
 640                 TAILQ_INIT((head2));                                    \
 641                 QMD_TRACE_HEAD(head1);                                  \
 642                 QMD_TRACE_HEAD(head2);                                  \
 643         }                                                               \
 644 } while (0)
 645
 646 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 647
 648 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 649
 650 #define TAILQ_FOREACH(var, head, field)                                 \
 651         for ((var) = TAILQ_FIRST((head));                               \
 652             (var);                                                      \
 653             (var) = TAILQ_NEXT((var), field))
 654
 655 #define TAILQ_FOREACH_FROM(var, head, field)                            \
 656         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 657             (var);                                                      \
 658             (var) = TAILQ_NEXT((var), field))
 659
 660 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 661         for ((var) = TAILQ_FIRST((head));                               \
 662             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 663             (var) = (tvar))
 664
 665 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 666         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 667             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 668             (var) = (tvar))
 669
 670 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 671         for ((var) = TAILQ_LAST((head), headname);                      \
 672             (var);                                                      \
 673             (var) = TAILQ_PREV((var), headname, field))
 674
 675 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)          \
 676         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 677             (var);                                                      \
 678             (var) = TAILQ_PREV((var), headname, field))
 679
 680 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 681         for ((var) = TAILQ_LAST((head), headname);                      \
 682             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 683             (var) = (tvar))
 684
 685 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
 686         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 687             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 688             (var) = (tvar))
 689
 690 #define TAILQ_INIT(head) do {                                           \
 691         TAILQ_FIRST((head)) = NULL;                                     \
 692         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 693         QMD_TRACE_HEAD(head);                                           \
 694 } while (0)
 695
 696 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 697         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 698         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 699                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 700                     &TAILQ_NEXT((elm), field);                          \
 701         else {                                                          \
 702                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 703                 QMD_TRACE_HEAD(head);                                   \
 704         }                                                               \
 705         TAILQ_NEXT((listelm), field) = (elm);                           \
 706         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 707         QMD_TRACE_ELEM(&(elm)->field);                                  \
 708         QMD_TRACE_ELEM(&(listelm)->field);                              \
 709 } while (0)
 710
 711 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 712         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 713         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 714         TAILQ_NEXT((elm), field) = (listelm);                           \
 715         *(listelm)->field.tqe_prev = (elm);                             \
 716         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 717         QMD_TRACE_ELEM(&(elm)->field);                                  \
 718         QMD_TRACE_ELEM(&(listelm)->field);                              \
 719 } while (0)
 720
 721 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 722         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 723         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 724                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 725                     &TAILQ_NEXT((elm), field);                          \
 726         else                                                            \
 727                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 728         TAILQ_FIRST((head)) = (elm);                                    \
 729         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 730         QMD_TRACE_HEAD(head);                                           \
 731         QMD_TRACE_ELEM(&(elm)->field);                                  \
 732 } while (0)
 733
 734 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 735         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 736         TAILQ_NEXT((elm), field) = NULL;                                \
 737         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 738         *(head)->tqh_last = (elm);                                      \
 739         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 740         QMD_TRACE_HEAD(head);                                           \
 741         QMD_TRACE_ELEM(&(elm)->field);                                  \
 742 } while (0)
 743
 744 #define TAILQ_LAST(head, headname)                                      \
 745         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 746
 747 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 748
 749 #define TAILQ_PREV(elm, headname, field)                                \
 750         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 751
 752 #define TAILQ_REMOVE(head, elm, field) do {                             \
 753         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 754         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 755         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 756         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 757         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 758                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 759                     (elm)->field.tqe_prev;                              \
 760         else {                                                          \
 761                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 762                 QMD_TRACE_HEAD(head);                                   \
 763         }                                                               \
 764         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 765         TRASHIT(*oldnext);                                              \
 766         TRASHIT(*oldprev);                                              \
 767         QMD_TRACE_ELEM(&(elm)->field);                                  \
 768 } while (0)
 769
 770 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 771         QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
 772         QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
 773         (head1)->tqh_first = (head2)->tqh_first;                        \
 774         (head1)->tqh_last = (head2)->tqh_last;                          \
 775         (head2)->tqh_first = swap_first;                                \
 776         (head2)->tqh_last = swap_last;                                  \
 777         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 778                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 779         else                                                            \
 780                 (head1)->tqh_last = &(head1)->tqh_first;                \
 781         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 782                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 783         else                                                            \
 784                 (head2)->tqh_last = &(head2)->tqh_first;                \
 785 } while (0)
 786
 787 #endif /* !_SYS_QUEUE_H_ */