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  * _LAST_FAST                   -       -       -       +
  97  * _FOREACH                     +       +       +       +
  98  * _FOREACH_FROM                +       +       +       +
  99  * _FOREACH_SAFE                +       +       +       +
 100  * _FOREACH_FROM_SAFE           +       +       +       +
 101  * _FOREACH_REVERSE             -       -       -       +
 102  * _FOREACH_REVERSE_FROM        -       -       -       +
 103  * _FOREACH_REVERSE_SAFE        -       -       -       +
 104  * _FOREACH_REVERSE_FROM_SAFE   -       -       -       +
 105  * _INSERT_HEAD                 +       +       +       +
 106  * _INSERT_BEFORE               -       +       -       +
 107  * _INSERT_AFTER                +       +       +       +
 108  * _INSERT_TAIL                 -       -       +       +
 109  * _CONCAT                      s       s       +       +
 110  * _REMOVE_AFTER                +       -       +       -
 111  * _REMOVE_HEAD                 +       -       +       -
 112  * _REMOVE                      s       +       s       +
 113  * _SWAP                        +       +       +       +
 114  *
 115  */
 116 #ifdef QUEUE_MACRO_DEBUG
 117 /* Store the last 2 places the queue element or head was altered */
 118 struct qm_trace {
 119         unsigned long    lastline;
 120         unsigned long    prevline;
 121         const char      *lastfile;
 122         const char      *prevfile;
 123 };
 124
 125 #define TRACEBUF        struct qm_trace trace;
 126 #define TRACEBUF_INITIALIZER    { __LINE__, 0, __FILE__, NULL } ,
 127 #define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
 128 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 129
 130 #define QMD_TRACE_HEAD(head) do {                                       \
 131         (head)->trace.prevline = (head)->trace.lastline;                \
 132         (head)->trace.prevfile = (head)->trace.lastfile;                \
 133         (head)->trace.lastline = __LINE__;                              \
 134         (head)->trace.lastfile = __FILE__;                              \
 135 } while (0)
 136
 137 #define QMD_TRACE_ELEM(elem) do {                                       \
 138         (elem)->trace.prevline = (elem)->trace.lastline;                \
 139         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 140         (elem)->trace.lastline = __LINE__;                              \
 141         (elem)->trace.lastfile = __FILE__;                              \
 142 } while (0)
 143
 144 #else
 145 #define QMD_TRACE_ELEM(elem)
 146 #define QMD_TRACE_HEAD(head)
 147 #define QMD_SAVELINK(name, link)
 148 #define TRACEBUF
 149 #define TRACEBUF_INITIALIZER
 150 #define TRASHIT(x)
 151 #endif  /* QUEUE_MACRO_DEBUG */
 152
 153 #ifdef __cplusplus
 154 /*
 155  * In C++ there can be structure lists and class lists:
 156  */
 157 #define QUEUE_TYPEOF(type) type
 158 #else
 159 #define QUEUE_TYPEOF(type) struct type
 160 #endif
 161
 162 /*
 163  * Singly-linked List declarations.
 164  */
 165 #define SLIST_HEAD(name, type)                                          \
 166 struct name {                                                           \
 167         struct type *slh_first; /* first element */                     \
 168 }
 169
 170 #define SLIST_CLASS_HEAD(name, type)                                    \
 171 struct name {                                                           \
 172         class type *slh_first;  /* first element */                     \
 173 }
 174
 175 #define SLIST_HEAD_INITIALIZER(head)                                    \
 176         { NULL }
 177
 178 #define SLIST_ENTRY(type)                                               \
 179 struct {                                                                \
 180         struct type *sle_next;  /* next element */                      \
 181 }
 182
 183 #define SLIST_CLASS_ENTRY(type)                                         \
 184 struct {                                                                \
 185         class type *sle_next;           /* next element */              \
 186 }
 187
 188 /*
 189  * Singly-linked List functions.
 190  */
 191 #define SLIST_CONCAT(head1, head2, type, field) do {                    \
 192         QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head1);                \
 193         if (curelm == NULL) {                                           \
 194                 if ((SLIST_FIRST(head1) = SLIST_FIRST(head2)) != NULL)  \
 195                         SLIST_INIT(head2);                              \
 196         } else if (SLIST_FIRST(head2) != NULL) {                        \
 197                 while (SLIST_NEXT(curelm, field) != NULL)               \
 198                         curelm = SLIST_NEXT(curelm, field);             \
 199                 SLIST_NEXT(curelm, field) = SLIST_FIRST(head2);         \
 200                 SLIST_INIT(head2);                                      \
 201         }                                                               \
 202 } while (0)
 203
 204 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 205
 206 #define SLIST_FIRST(head)       ((head)->slh_first)
 207
 208 #define SLIST_FOREACH(var, head, field)                                 \
 209         for ((var) = SLIST_FIRST((head));                               \
 210             (var);                                                      \
 211             (var) = SLIST_NEXT((var), field))
 212
 213 #define SLIST_FOREACH_FROM(var, head, field)                            \
 214         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 215             (var);                                                      \
 216             (var) = SLIST_NEXT((var), field))
 217
 218 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 219         for ((var) = SLIST_FIRST((head));                               \
 220             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 221             (var) = (tvar))
 222
 223 #define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 224         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 225             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 226             (var) = (tvar))
 227
 228 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 229         for ((varp) = &SLIST_FIRST((head));                             \
 230             ((var) = *(varp)) != NULL;                                  \
 231             (varp) = &SLIST_NEXT((var), field))
 232
 233 #define SLIST_INIT(head) do {                                           \
 234         SLIST_FIRST((head)) = NULL;                                     \
 235 } while (0)
 236
 237 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 238         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 239         SLIST_NEXT((slistelm), field) = (elm);                          \
 240 } while (0)
 241
 242 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 243         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 244         SLIST_FIRST((head)) = (elm);                                    \
 245 } while (0)
 246
 247 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 248
 249 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 250         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 251         if (SLIST_FIRST((head)) == (elm)) {                             \
 252                 SLIST_REMOVE_HEAD((head), field);                       \
 253         }                                                               \
 254         else {                                                          \
 255                 QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head);         \
 256                 while (SLIST_NEXT(curelm, field) != (elm))              \
 257                         curelm = SLIST_NEXT(curelm, field);             \
 258                 SLIST_REMOVE_AFTER(curelm, field);                      \
 259         }                                                               \
 260         TRASHIT(*oldnext);                                              \
 261 } while (0)
 262
 263 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 264         SLIST_NEXT(elm, field) =                                        \
 265             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 266 } while (0)
 267
 268 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 269         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 270 } while (0)
 271
 272 #define SLIST_SWAP(head1, head2, type) do {                             \
 273         QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
 274         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
 275         SLIST_FIRST(head2) = swap_first;                                \
 276 } while (0)
 277
 278 /*
 279  * Singly-linked Tail queue declarations.
 280  */
 281 #define STAILQ_HEAD(name, type)                                         \
 282 struct name {                                                           \
 283         struct type *stqh_first;/* first element */                     \
 284         struct type **stqh_last;/* addr of last next element */         \
 285 }
 286
 287 #define STAILQ_CLASS_HEAD(name, type)                                   \
 288 struct name {                                                           \
 289         class type *stqh_first; /* first element */                     \
 290         class type **stqh_last; /* addr of last next element */         \
 291 }
 292
 293 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 294         { NULL, &(head).stqh_first }
 295
 296 #define STAILQ_ENTRY(type)                                              \
 297 struct {                                                                \
 298         struct type *stqe_next; /* next element */                      \
 299 }
 300
 301 #define STAILQ_CLASS_ENTRY(type)                                        \
 302 struct {                                                                \
 303         class type *stqe_next;  /* next element */                      \
 304 }
 305
 306 /*
 307  * Singly-linked Tail queue functions.
 308  */
 309 #define STAILQ_CONCAT(head1, head2) do {                                \
 310         if (!STAILQ_EMPTY((head2))) {                                   \
 311                 *(head1)->stqh_last = (head2)->stqh_first;              \
 312                 (head1)->stqh_last = (head2)->stqh_last;                \
 313                 STAILQ_INIT((head2));                                   \
 314         }                                                               \
 315 } while (0)
 316
 317 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 318
 319 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 320
 321 #define STAILQ_FOREACH(var, head, field)                                \
 322         for((var) = STAILQ_FIRST((head));                               \
 323            (var);                                                       \
 324            (var) = STAILQ_NEXT((var), field))
 325
 326 #define STAILQ_FOREACH_FROM(var, head, field)                           \
 327         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 328            (var);                                                       \
 329            (var) = STAILQ_NEXT((var), field))
 330
 331 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 332         for ((var) = STAILQ_FIRST((head));                              \
 333             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 334             (var) = (tvar))
 335
 336 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
 337         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 338             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 339             (var) = (tvar))
 340
 341 #define STAILQ_INIT(head) do {                                          \
 342         STAILQ_FIRST((head)) = NULL;                                    \
 343         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 344 } while (0)
 345
 346 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 347         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 348                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 349         STAILQ_NEXT((tqelm), field) = (elm);                            \
 350 } while (0)
 351
 352 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 353         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 354                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 355         STAILQ_FIRST((head)) = (elm);                                   \
 356 } while (0)
 357
 358 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 359         STAILQ_NEXT((elm), field) = NULL;                               \
 360         *(head)->stqh_last = (elm);                                     \
 361         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 362 } while (0)
 363
 364 #define STAILQ_LAST(head, type, field)                          \
 365         (STAILQ_EMPTY((head)) ? NULL :                          \
 366             __containerof((head)->stqh_last,                    \
 367             QUEUE_TYPEOF(type), field.stqe_next))
 368
 369 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 370
 371 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 372         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 373         if (STAILQ_FIRST((head)) == (elm)) {                            \
 374                 STAILQ_REMOVE_HEAD((head), field);                      \
 375         }                                                               \
 376         else {                                                          \
 377                 QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
 378                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 379                         curelm = STAILQ_NEXT(curelm, field);            \
 380                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 381         }                                                               \
 382         TRASHIT(*oldnext);                                              \
 383 } while (0)
 384
 385 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 386         if ((STAILQ_NEXT(elm, field) =                                  \
 387              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 388                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 389 } while (0)
 390
 391 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 392         if ((STAILQ_FIRST((head)) =                                     \
 393              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 394                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 395 } while (0)
 396
 397 #define STAILQ_SWAP(head1, head2, type) do {                            \
 398         QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
 399         QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
 400         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 401         (head1)->stqh_last = (head2)->stqh_last;                        \
 402         STAILQ_FIRST(head2) = swap_first;                               \
 403         (head2)->stqh_last = swap_last;                                 \
 404         if (STAILQ_EMPTY(head1))                                        \
 405                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 406         if (STAILQ_EMPTY(head2))                                        \
 407                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 408 } while (0)
 409
 410
 411 /*
 412  * List declarations.
 413  */
 414 #define LIST_HEAD(name, type)                                           \
 415 struct name {                                                           \
 416         struct type *lh_first;  /* first element */                     \
 417 }
 418
 419 #define LIST_CLASS_HEAD(name, type)                                     \
 420 struct name {                                                           \
 421         class type *lh_first;   /* first element */                     \
 422 }
 423
 424 #define LIST_HEAD_INITIALIZER(head)                                     \
 425         { NULL }
 426
 427 #define LIST_ENTRY(type)                                                \
 428 struct {                                                                \
 429         struct type *le_next;   /* next element */                      \
 430         struct type **le_prev;  /* address of previous next element */  \
 431 }
 432
 433 #define LIST_CLASS_ENTRY(type)                                          \
 434 struct {                                                                \
 435         class type *le_next;    /* next element */                      \
 436         class type **le_prev;   /* address of previous next element */  \
 437 }
 438
 439 /*
 440  * List functions.
 441  */
 442
 443 #if (defined(_KERNEL) && defined(INVARIANTS))
 444 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 445         if (LIST_FIRST((head)) != NULL &&                               \
 446             LIST_FIRST((head))->field.le_prev !=                        \
 447              &LIST_FIRST((head)))                                       \
 448                 panic("Bad list head %p first->prev != head", (head));  \
 449 } while (0)
 450
 451 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 452         if (LIST_NEXT((elm), field) != NULL &&                          \
 453             LIST_NEXT((elm), field)->field.le_prev !=                   \
 454              &((elm)->field.le_next))                                   \
 455                 panic("Bad link elm %p next->prev != elm", (elm));      \
 456 } while (0)
 457
 458 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 459         if (*(elm)->field.le_prev != (elm))                             \
 460                 panic("Bad link elm %p prev->next != elm", (elm));      \
 461 } while (0)
 462 #else
 463 #define QMD_LIST_CHECK_HEAD(head, field)
 464 #define QMD_LIST_CHECK_NEXT(elm, field)
 465 #define QMD_LIST_CHECK_PREV(elm, field)
 466 #endif /* (_KERNEL && INVARIANTS) */
 467
 468 #define LIST_CONCAT(head1, head2, type, field) do {                           \
 469         QUEUE_TYPEOF(type) *curelm = LIST_FIRST(head1);                       \
 470         if (curelm == NULL) {                                                 \
 471                 if ((LIST_FIRST(head1) = LIST_FIRST(head2)) != NULL) {        \
 472                         LIST_FIRST(head2)->field.le_prev =                    \
 473                             &LIST_FIRST((head1));                             \
 474                         LIST_INIT(head2);                                     \
 475                 }                                                             \
 476         } else if (LIST_FIRST(head2) != NULL) {                               \
 477                 while (LIST_NEXT(curelm, field) != NULL)                      \
 478                         curelm = LIST_NEXT(curelm, field);                    \
 479                 LIST_NEXT(curelm, field) = LIST_FIRST(head2);                 \
 480                 LIST_FIRST(head2)->field.le_prev = &LIST_NEXT(curelm, field); \
 481                 LIST_INIT(head2);                                             \
 482         }                                                                     \
 483 } while (0)
 484
 485 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 486
 487 #define LIST_FIRST(head)        ((head)->lh_first)
 488
 489 #define LIST_FOREACH(var, head, field)                                  \
 490         for ((var) = LIST_FIRST((head));                                \
 491             (var);                                                      \
 492             (var) = LIST_NEXT((var), field))
 493
 494 #define LIST_FOREACH_FROM(var, head, field)                             \
 495         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 496             (var);                                                      \
 497             (var) = LIST_NEXT((var), field))
 498
 499 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 500         for ((var) = LIST_FIRST((head));                                \
 501             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 502             (var) = (tvar))
 503
 504 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
 505         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 506             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 507             (var) = (tvar))
 508
 509 #define LIST_INIT(head) do {                                            \
 510         LIST_FIRST((head)) = NULL;                                      \
 511 } while (0)
 512
 513 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 514         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 515         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 516                 LIST_NEXT((listelm), field)->field.le_prev =            \
 517                     &LIST_NEXT((elm), field);                           \
 518         LIST_NEXT((listelm), field) = (elm);                            \
 519         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 520 } while (0)
 521
 522 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 523         QMD_LIST_CHECK_PREV(listelm, field);                            \
 524         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 525         LIST_NEXT((elm), field) = (listelm);                            \
 526         *(listelm)->field.le_prev = (elm);                              \
 527         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 528 } while (0)
 529
 530 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 531         QMD_LIST_CHECK_HEAD((head), field);                             \
 532         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 533                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 534         LIST_FIRST((head)) = (elm);                                     \
 535         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 536 } while (0)
 537
 538 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 539
 540 #define LIST_PREV(elm, head, type, field)                       \
 541         ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
 542             __containerof((elm)->field.le_prev,                 \
 543             QUEUE_TYPEOF(type), field.le_next))
 544
 545 #define LIST_REMOVE(elm, field) do {                                    \
 546         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 547         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 548         QMD_LIST_CHECK_NEXT(elm, field);                                \
 549         QMD_LIST_CHECK_PREV(elm, field);                                \
 550         if (LIST_NEXT((elm), field) != NULL)                            \
 551                 LIST_NEXT((elm), field)->field.le_prev =                \
 552                     (elm)->field.le_prev;                               \
 553         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 554         TRASHIT(*oldnext);                                              \
 555         TRASHIT(*oldprev);                                              \
 556 } while (0)
 557
 558 #define LIST_SWAP(head1, head2, type, field) do {                       \
 559         QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
 560         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 561         LIST_FIRST((head2)) = swap_tmp;                                 \
 562         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 563                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 564         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 565                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 566 } while (0)
 567
 568 /*
 569  * Tail queue declarations.
 570  */
 571 #define TAILQ_HEAD(name, type)                                          \
 572 struct name {                                                           \
 573         struct type *tqh_first; /* first element */                     \
 574         struct type **tqh_last; /* addr of last next element */         \
 575         TRACEBUF                                                        \
 576 }
 577
 578 #define TAILQ_CLASS_HEAD(name, type)                                    \
 579 struct name {                                                           \
 580         class type *tqh_first;  /* first element */                     \
 581         class type **tqh_last;  /* addr of last next element */         \
 582         TRACEBUF                                                        \
 583 }
 584
 585 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 586         { NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }
 587
 588 #define TAILQ_ENTRY(type)                                               \
 589 struct {                                                                \
 590         struct type *tqe_next;  /* next element */                      \
 591         struct type **tqe_prev; /* address of previous next element */  \
 592         TRACEBUF                                                        \
 593 }
 594
 595 #define TAILQ_CLASS_ENTRY(type)                                         \
 596 struct {                                                                \
 597         class type *tqe_next;   /* next element */                      \
 598         class type **tqe_prev;  /* address of previous next element */  \
 599         TRACEBUF                                                        \
 600 }
 601
 602 /*
 603  * Tail queue functions.
 604  */
 605 #if (defined(_KERNEL) && defined(INVARIANTS))
 606 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 607         if (!TAILQ_EMPTY(head) &&                                       \
 608             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 609              &TAILQ_FIRST((head)))                                      \
 610                 panic("Bad tailq head %p first->prev != head", (head)); \
 611 } while (0)
 612
 613 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 614         if (*(head)->tqh_last != NULL)                                  \
 615                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 616 } while (0)
 617
 618 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 619         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 620             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 621              &((elm)->field.tqe_next))                                  \
 622                 panic("Bad link elm %p next->prev != elm", (elm));      \
 623 } while (0)
 624
 625 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 626         if (*(elm)->field.tqe_prev != (elm))                            \
 627                 panic("Bad link elm %p prev->next != elm", (elm));      \
 628 } while (0)
 629 #else
 630 #define QMD_TAILQ_CHECK_HEAD(head, field)
 631 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 632 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 633 #define QMD_TAILQ_CHECK_PREV(elm, field)
 634 #endif /* (_KERNEL && INVARIANTS) */
 635
 636 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 637         if (!TAILQ_EMPTY(head2)) {                                      \
 638                 *(head1)->tqh_last = (head2)->tqh_first;                \
 639                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 640                 (head1)->tqh_last = (head2)->tqh_last;                  \
 641                 TAILQ_INIT((head2));                                    \
 642                 QMD_TRACE_HEAD(head1);                                  \
 643                 QMD_TRACE_HEAD(head2);                                  \
 644         }                                                               \
 645 } while (0)
 646
 647 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 648
 649 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 650
 651 #define TAILQ_FOREACH(var, head, field)                                 \
 652         for ((var) = TAILQ_FIRST((head));                               \
 653             (var);                                                      \
 654             (var) = TAILQ_NEXT((var), field))
 655
 656 #define TAILQ_FOREACH_FROM(var, head, field)                            \
 657         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 658             (var);                                                      \
 659             (var) = TAILQ_NEXT((var), field))
 660
 661 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 662         for ((var) = TAILQ_FIRST((head));                               \
 663             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 664             (var) = (tvar))
 665
 666 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 667         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 668             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 669             (var) = (tvar))
 670
 671 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 672         for ((var) = TAILQ_LAST((head), headname);                      \
 673             (var);                                                      \
 674             (var) = TAILQ_PREV((var), headname, field))
 675
 676 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)          \
 677         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 678             (var);                                                      \
 679             (var) = TAILQ_PREV((var), headname, field))
 680
 681 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 682         for ((var) = TAILQ_LAST((head), headname);                      \
 683             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 684             (var) = (tvar))
 685
 686 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
 687         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 688             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 689             (var) = (tvar))
 690
 691 #define TAILQ_INIT(head) do {                                           \
 692         TAILQ_FIRST((head)) = NULL;                                     \
 693         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 694         QMD_TRACE_HEAD(head);                                           \
 695 } while (0)
 696
 697 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 698         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 699         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 700                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 701                     &TAILQ_NEXT((elm), field);                          \
 702         else {                                                          \
 703                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 704                 QMD_TRACE_HEAD(head);                                   \
 705         }                                                               \
 706         TAILQ_NEXT((listelm), field) = (elm);                           \
 707         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 708         QMD_TRACE_ELEM(&(elm)->field);                                  \
 709         QMD_TRACE_ELEM(&(listelm)->field);                              \
 710 } while (0)
 711
 712 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 713         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 714         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 715         TAILQ_NEXT((elm), field) = (listelm);                           \
 716         *(listelm)->field.tqe_prev = (elm);                             \
 717         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 718         QMD_TRACE_ELEM(&(elm)->field);                                  \
 719         QMD_TRACE_ELEM(&(listelm)->field);                              \
 720 } while (0)
 721
 722 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 723         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 724         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 725                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 726                     &TAILQ_NEXT((elm), field);                          \
 727         else                                                            \
 728                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 729         TAILQ_FIRST((head)) = (elm);                                    \
 730         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 731         QMD_TRACE_HEAD(head);                                           \
 732         QMD_TRACE_ELEM(&(elm)->field);                                  \
 733 } while (0)
 734
 735 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 736         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 737         TAILQ_NEXT((elm), field) = NULL;                                \
 738         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 739         *(head)->tqh_last = (elm);                                      \
 740         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 741         QMD_TRACE_HEAD(head);                                           \
 742         QMD_TRACE_ELEM(&(elm)->field);                                  \
 743 } while (0)
 744
 745 #define TAILQ_LAST(head, headname)                                      \
 746         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 747
 748 /*
 749  * The FAST function is fast in that it causes no data access other
 750  * then the access to the head. The standard LAST function above
 751  * will cause a data access of both the element you want and
 752  * the previous element. FAST is very useful for instances when
 753  * you may want to prefetch the last data element.
 754  */
 755 #define TAILQ_LAST_FAST(head, type, field)                      \
 756     (TAILQ_EMPTY(head) ? NULL : __containerof((head)->tqh_last, QUEUE_TYPEOF(type), field.tqe_next))
 757
 758 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 759
 760 #define TAILQ_PREV(elm, headname, field)                                \
 761         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 762
 763 #define TAILQ_REMOVE(head, elm, field) do {                             \
 764         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 765         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 766         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 767         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 768         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 769                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 770                     (elm)->field.tqe_prev;                              \
 771         else {                                                          \
 772                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 773                 QMD_TRACE_HEAD(head);                                   \
 774         }                                                               \
 775         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 776         TRASHIT(*oldnext);                                              \
 777         TRASHIT(*oldprev);                                              \
 778         QMD_TRACE_ELEM(&(elm)->field);                                  \
 779 } while (0)
 780
 781 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 782         QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
 783         QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
 784         (head1)->tqh_first = (head2)->tqh_first;                        \
 785         (head1)->tqh_last = (head2)->tqh_last;                          \
 786         (head2)->tqh_first = swap_first;                                \
 787         (head2)->tqh_last = swap_last;                                  \
 788         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 789                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 790         else                                                            \
 791                 (head1)->tqh_last = &(head1)->tqh_first;                \
 792         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 793                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 794         else                                                            \
 795                 (head2)->tqh_last = &(head2)->tqh_first;                \
 796 } while (0)
 797
 798 #endif /* !_SYS_QUEUE_H_ */