sys/sys/queue.h

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1991, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  *      @(#)queue.h     8.5 (Berkeley) 8/20/94
  32  * $FreeBSD$
  33  */
  34
  35 #ifndef _SYS_QUEUE_H_
  36 #define _SYS_QUEUE_H_
  37
  38 #include <sys/cdefs.h>
  39
  40 /*
  41  * This file defines four types of data structures: singly-linked lists,
  42  * singly-linked tail queues, lists and tail queues.
  43  *
  44  * A singly-linked list is headed by a single forward pointer. The elements
  45  * are singly linked for minimum space and pointer manipulation overhead at
  46  * the expense of O(n) removal for arbitrary elements. New elements can be
  47  * added to the list after an existing element or at the head of the list.
  48  * Elements being removed from the head of the list should use the explicit
  49  * macro for this purpose for optimum efficiency. A singly-linked list may
  50  * only be traversed in the forward direction.  Singly-linked lists are ideal
  51  * for applications with large datasets and few or no removals or for
  52  * implementing a LIFO queue.
  53  *
  54  * A singly-linked tail queue is headed by a pair of pointers, one to the
  55  * head of the list and the other to the tail of the list. The elements are
  56  * singly linked for minimum space and pointer manipulation overhead at the
  57  * expense of O(n) removal for arbitrary elements. New elements can be added
  58  * to the list after an existing element, at the head of the list, or at the
  59  * end of the list. Elements being removed from the head of the tail queue
  60  * should use the explicit macro for this purpose for optimum efficiency.
  61  * A singly-linked tail queue may only be traversed in the forward direction.
  62  * Singly-linked tail queues are ideal for applications with large datasets
  63  * and few or no removals or for implementing a FIFO queue.
  64  *
  65  * A list is headed by a single forward pointer (or an array of forward
  66  * pointers for a hash table header). The elements are doubly linked
  67  * so that an arbitrary element can be removed without a need to
  68  * traverse the list. New elements can be added to the list before
  69  * or after an existing element or at the head of the list. A list
  70  * may be traversed in either direction.
  71  *
  72  * A tail queue is headed by a pair of pointers, one to the head of the
  73  * list and the other to the tail of the list. The elements are doubly
  74  * linked so that an arbitrary element can be removed without a need to
  75  * traverse the list. New elements can be added to the list before or
  76  * after an existing element, at the head of the list, or at the end of
  77  * the list. A tail queue may be traversed in either direction.
  78  *
  79  * For details on the use of these macros, see the queue(3) manual page.
  80  *
  81  * Below is a summary of implemented functions where:
  82  *  +  means the macro is available
  83  *  -  means the macro is not available
  84  *  s  means the macro is available but is slow (runs in O(n) time)
  85  *
  86  *                              SLIST   LIST    STAILQ  TAILQ
  87  * _HEAD                        +       +       +       +
  88  * _CLASS_HEAD                  +       +       +       +
  89  * _HEAD_INITIALIZER            +       +       +       +
  90  * _ENTRY                       +       +       +       +
  91  * _CLASS_ENTRY                 +       +       +       +
  92  * _INIT                        +       +       +       +
  93  * _EMPTY                       +       +       +       +
  94  * _FIRST                       +       +       +       +
  95  * _NEXT                        +       +       +       +
  96  * _PREV                        -       +       -       +
  97  * _LAST                        -       -       +       +
  98  * _LAST_FAST                   -       -       -       +
  99  * _FOREACH                     +       +       +       +
 100  * _FOREACH_FROM                +       +       +       +
 101  * _FOREACH_SAFE                +       +       +       +
 102  * _FOREACH_FROM_SAFE           +       +       +       +
 103  * _FOREACH_REVERSE             -       -       -       +
 104  * _FOREACH_REVERSE_FROM        -       -       -       +
 105  * _FOREACH_REVERSE_SAFE        -       -       -       +
 106  * _FOREACH_REVERSE_FROM_SAFE   -       -       -       +
 107  * _INSERT_HEAD                 +       +       +       +
 108  * _INSERT_BEFORE               -       +       -       +
 109  * _INSERT_AFTER                +       +       +       +
 110  * _INSERT_TAIL                 -       -       +       +
 111  * _CONCAT                      s       s       +       +
 112  * _REMOVE_AFTER                +       -       +       -
 113  * _REMOVE_HEAD                 +       -       +       -
 114  * _REMOVE                      s       +       s       +
 115  * _SWAP                        +       +       +       +
 116  *
 117  */
 118 #ifdef QUEUE_MACRO_DEBUG
 119 #warn Use QUEUE_MACRO_DEBUG_TRACE and/or QUEUE_MACRO_DEBUG_TRASH
 120 #define QUEUE_MACRO_DEBUG_TRACE
 121 #define QUEUE_MACRO_DEBUG_TRASH
 122 #endif
 123
 124 #ifdef QUEUE_MACRO_DEBUG_TRACE
 125 /* Store the last 2 places the queue element or head was altered */
 126 struct qm_trace {
 127         unsigned long    lastline;
 128         unsigned long    prevline;
 129         const char      *lastfile;
 130         const char      *prevfile;
 131 };
 132
 133 #define TRACEBUF        struct qm_trace trace;
 134 #define TRACEBUF_INITIALIZER    { __LINE__, 0, __FILE__, NULL } ,
 135
 136 #define QMD_TRACE_HEAD(head) do {                                       \
 137         (head)->trace.prevline = (head)->trace.lastline;                \
 138         (head)->trace.prevfile = (head)->trace.lastfile;                \
 139         (head)->trace.lastline = __LINE__;                              \
 140         (head)->trace.lastfile = __FILE__;                              \
 141 } while (0)
 142
 143 #define QMD_TRACE_ELEM(elem) do {                                       \
 144         (elem)->trace.prevline = (elem)->trace.lastline;                \
 145         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 146         (elem)->trace.lastline = __LINE__;                              \
 147         (elem)->trace.lastfile = __FILE__;                              \
 148 } while (0)
 149
 150 #else   /* !QUEUE_MACRO_DEBUG_TRACE */
 151 #define QMD_TRACE_ELEM(elem)
 152 #define QMD_TRACE_HEAD(head)
 153 #define TRACEBUF
 154 #define TRACEBUF_INITIALIZER
 155 #endif  /* QUEUE_MACRO_DEBUG_TRACE */
 156
 157 #ifdef QUEUE_MACRO_DEBUG_TRASH
 158 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 159 #define TRASHIT(x)              do {(x) = (void *)-1;} while (0)
 160 #define QMD_IS_TRASHED(x)       ((x) == (void *)(intptr_t)-1)
 161 #else   /* !QUEUE_MACRO_DEBUG_TRASH */
 162 #define QMD_SAVELINK(name, link)
 163 #define TRASHIT(x)
 164 #define QMD_IS_TRASHED(x)       0
 165 #endif  /* QUEUE_MACRO_DEBUG_TRASH */
 166
 167 #ifdef __cplusplus
 168 /*
 169  * In C++ there can be structure lists and class lists:
 170  */
 171 #define QUEUE_TYPEOF(type) type
 172 #else
 173 #define QUEUE_TYPEOF(type) struct type
 174 #endif
 175
 176 /*
 177  * Singly-linked List declarations.
 178  */
 179 #define SLIST_HEAD(name, type)                                          \
 180 struct name {                                                           \
 181         struct type *slh_first; /* first element */                     \
 182 }
 183
 184 #define SLIST_CLASS_HEAD(name, type)                                    \
 185 struct name {                                                           \
 186         class type *slh_first;  /* first element */                     \
 187 }
 188
 189 #define SLIST_HEAD_INITIALIZER(head)                                    \
 190         { NULL }
 191
 192 #define SLIST_ENTRY(type)                                               \
 193 struct {                                                                \
 194         struct type *sle_next;  /* next element */                      \
 195 }
 196
 197 #define SLIST_CLASS_ENTRY(type)                                         \
 198 struct {                                                                \
 199         class type *sle_next;           /* next element */              \
 200 }
 201
 202 /*
 203  * Singly-linked List functions.
 204  */
 205 #if (defined(_KERNEL) && defined(INVARIANTS))
 206 #define QMD_SLIST_CHECK_PREVPTR(prevp, elm) do {                        \
 207         if (*(prevp) != (elm))                                          \
 208                 panic("Bad prevptr *(%p) == %p != %p",                  \
 209                     (prevp), *(prevp), (elm));                          \
 210 } while (0)
 211 #else
 212 #define QMD_SLIST_CHECK_PREVPTR(prevp, elm)
 213 #endif
 214
 215 #define SLIST_CONCAT(head1, head2, type, field) do {                    \
 216         QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head1);                \
 217         if (curelm == NULL) {                                           \
 218                 if ((SLIST_FIRST(head1) = SLIST_FIRST(head2)) != NULL)  \
 219                         SLIST_INIT(head2);                              \
 220         } else if (SLIST_FIRST(head2) != NULL) {                        \
 221                 while (SLIST_NEXT(curelm, field) != NULL)               \
 222                         curelm = SLIST_NEXT(curelm, field);             \
 223                 SLIST_NEXT(curelm, field) = SLIST_FIRST(head2);         \
 224                 SLIST_INIT(head2);                                      \
 225         }                                                               \
 226 } while (0)
 227
 228 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 229
 230 #define SLIST_FIRST(head)       ((head)->slh_first)
 231
 232 #define SLIST_FOREACH(var, head, field)                                 \
 233         for ((var) = SLIST_FIRST((head));                               \
 234             (var);                                                      \
 235             (var) = SLIST_NEXT((var), field))
 236
 237 #define SLIST_FOREACH_FROM(var, head, field)                            \
 238         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 239             (var);                                                      \
 240             (var) = SLIST_NEXT((var), field))
 241
 242 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 243         for ((var) = SLIST_FIRST((head));                               \
 244             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 245             (var) = (tvar))
 246
 247 #define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 248         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 249             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 250             (var) = (tvar))
 251
 252 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 253         for ((varp) = &SLIST_FIRST((head));                             \
 254             ((var) = *(varp)) != NULL;                                  \
 255             (varp) = &SLIST_NEXT((var), field))
 256
 257 #define SLIST_INIT(head) do {                                           \
 258         SLIST_FIRST((head)) = NULL;                                     \
 259 } while (0)
 260
 261 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 262         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 263         SLIST_NEXT((slistelm), field) = (elm);                          \
 264 } while (0)
 265
 266 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 267         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 268         SLIST_FIRST((head)) = (elm);                                    \
 269 } while (0)
 270
 271 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 272
 273 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 274         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 275         if (SLIST_FIRST((head)) == (elm)) {                             \
 276                 SLIST_REMOVE_HEAD((head), field);                       \
 277         }                                                               \
 278         else {                                                          \
 279                 QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head);         \
 280                 while (SLIST_NEXT(curelm, field) != (elm))              \
 281                         curelm = SLIST_NEXT(curelm, field);             \
 282                 SLIST_REMOVE_AFTER(curelm, field);                      \
 283         }                                                               \
 284         TRASHIT(*oldnext);                                              \
 285 } while (0)
 286
 287 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 288         SLIST_NEXT(elm, field) =                                        \
 289             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 290 } while (0)
 291
 292 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 293         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 294 } while (0)
 295
 296 #define SLIST_REMOVE_PREVPTR(prevp, elm, field) do {                    \
 297         QMD_SLIST_CHECK_PREVPTR(prevp, elm);                            \
 298         *(prevp) = SLIST_NEXT(elm, field);                              \
 299         TRASHIT((elm)->field.sle_next);                                 \
 300 } while (0)
 301
 302 #define SLIST_SWAP(head1, head2, type) do {                             \
 303         QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
 304         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
 305         SLIST_FIRST(head2) = swap_first;                                \
 306 } while (0)
 307
 308 /*
 309  * Singly-linked Tail queue declarations.
 310  */
 311 #define STAILQ_HEAD(name, type)                                         \
 312 struct name {                                                           \
 313         struct type *stqh_first;/* first element */                     \
 314         struct type **stqh_last;/* addr of last next element */         \
 315 }
 316
 317 #define STAILQ_CLASS_HEAD(name, type)                                   \
 318 struct name {                                                           \
 319         class type *stqh_first; /* first element */                     \
 320         class type **stqh_last; /* addr of last next element */         \
 321 }
 322
 323 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 324         { NULL, &(head).stqh_first }
 325
 326 #define STAILQ_ENTRY(type)                                              \
 327 struct {                                                                \
 328         struct type *stqe_next; /* next element */                      \
 329 }
 330
 331 #define STAILQ_CLASS_ENTRY(type)                                        \
 332 struct {                                                                \
 333         class type *stqe_next;  /* next element */                      \
 334 }
 335
 336 /*
 337  * Singly-linked Tail queue functions.
 338  */
 339 #define STAILQ_CONCAT(head1, head2) do {                                \
 340         if (!STAILQ_EMPTY((head2))) {                                   \
 341                 *(head1)->stqh_last = (head2)->stqh_first;              \
 342                 (head1)->stqh_last = (head2)->stqh_last;                \
 343                 STAILQ_INIT((head2));                                   \
 344         }                                                               \
 345 } while (0)
 346
 347 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 348
 349 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 350
 351 #define STAILQ_FOREACH(var, head, field)                                \
 352         for((var) = STAILQ_FIRST((head));                               \
 353            (var);                                                       \
 354            (var) = STAILQ_NEXT((var), field))
 355
 356 #define STAILQ_FOREACH_FROM(var, head, field)                           \
 357         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 358            (var);                                                       \
 359            (var) = STAILQ_NEXT((var), field))
 360
 361 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 362         for ((var) = STAILQ_FIRST((head));                              \
 363             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 364             (var) = (tvar))
 365
 366 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
 367         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 368             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 369             (var) = (tvar))
 370
 371 #define STAILQ_INIT(head) do {                                          \
 372         STAILQ_FIRST((head)) = NULL;                                    \
 373         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 374 } while (0)
 375
 376 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 377         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 378                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 379         STAILQ_NEXT((tqelm), field) = (elm);                            \
 380 } while (0)
 381
 382 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 383         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 384                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 385         STAILQ_FIRST((head)) = (elm);                                   \
 386 } while (0)
 387
 388 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 389         STAILQ_NEXT((elm), field) = NULL;                               \
 390         *(head)->stqh_last = (elm);                                     \
 391         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 392 } while (0)
 393
 394 #define STAILQ_LAST(head, type, field)                          \
 395         (STAILQ_EMPTY((head)) ? NULL :                          \
 396             __containerof((head)->stqh_last,                    \
 397             QUEUE_TYPEOF(type), field.stqe_next))
 398
 399 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 400
 401 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 402         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 403         if (STAILQ_FIRST((head)) == (elm)) {                            \
 404                 STAILQ_REMOVE_HEAD((head), field);                      \
 405         }                                                               \
 406         else {                                                          \
 407                 QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
 408                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 409                         curelm = STAILQ_NEXT(curelm, field);            \
 410                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 411         }                                                               \
 412         TRASHIT(*oldnext);                                              \
 413 } while (0)
 414
 415 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 416         if ((STAILQ_NEXT(elm, field) =                                  \
 417              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 418                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 419 } while (0)
 420
 421 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 422         if ((STAILQ_FIRST((head)) =                                     \
 423              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 424                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 425 } while (0)
 426
 427 #define STAILQ_SWAP(head1, head2, type) do {                            \
 428         QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
 429         QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
 430         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 431         (head1)->stqh_last = (head2)->stqh_last;                        \
 432         STAILQ_FIRST(head2) = swap_first;                               \
 433         (head2)->stqh_last = swap_last;                                 \
 434         if (STAILQ_EMPTY(head1))                                        \
 435                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 436         if (STAILQ_EMPTY(head2))                                        \
 437                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 438 } while (0)
 439
 440
 441 /*
 442  * List declarations.
 443  */
 444 #define LIST_HEAD(name, type)                                           \
 445 struct name {                                                           \
 446         struct type *lh_first;  /* first element */                     \
 447 }
 448
 449 #define LIST_CLASS_HEAD(name, type)                                     \
 450 struct name {                                                           \
 451         class type *lh_first;   /* first element */                     \
 452 }
 453
 454 #define LIST_HEAD_INITIALIZER(head)                                     \
 455         { NULL }
 456
 457 #define LIST_ENTRY(type)                                                \
 458 struct {                                                                \
 459         struct type *le_next;   /* next element */                      \
 460         struct type **le_prev;  /* address of previous next element */  \
 461 }
 462
 463 #define LIST_CLASS_ENTRY(type)                                          \
 464 struct {                                                                \
 465         class type *le_next;    /* next element */                      \
 466         class type **le_prev;   /* address of previous next element */  \
 467 }
 468
 469 /*
 470  * List functions.
 471  */
 472
 473 #if (defined(_KERNEL) && defined(INVARIANTS))
 474 /*
 475  * QMD_LIST_CHECK_HEAD(LIST_HEAD *head, LIST_ENTRY NAME)
 476  *
 477  * If the list is non-empty, validates that the first element of the list
 478  * points back at 'head.'
 479  */
 480 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 481         if (LIST_FIRST((head)) != NULL &&                               \
 482             LIST_FIRST((head))->field.le_prev !=                        \
 483              &LIST_FIRST((head)))                                       \
 484                 panic("Bad list head %p first->prev != head", (head));  \
 485 } while (0)
 486
 487 /*
 488  * QMD_LIST_CHECK_NEXT(TYPE *elm, LIST_ENTRY NAME)
 489  *
 490  * If an element follows 'elm' in the list, validates that the next element
 491  * points back at 'elm.'
 492  */
 493 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 494         if (LIST_NEXT((elm), field) != NULL &&                          \
 495             LIST_NEXT((elm), field)->field.le_prev !=                   \
 496              &((elm)->field.le_next))                                   \
 497                 panic("Bad link elm %p next->prev != elm", (elm));      \
 498 } while (0)
 499
 500 /*
 501  * QMD_LIST_CHECK_PREV(TYPE *elm, LIST_ENTRY NAME)
 502  *
 503  * Validates that the previous element (or head of the list) points to 'elm.'
 504  */
 505 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 506         if (*(elm)->field.le_prev != (elm))                             \
 507                 panic("Bad link elm %p prev->next != elm", (elm));      \
 508 } while (0)
 509 #else
 510 #define QMD_LIST_CHECK_HEAD(head, field)
 511 #define QMD_LIST_CHECK_NEXT(elm, field)
 512 #define QMD_LIST_CHECK_PREV(elm, field)
 513 #endif /* (_KERNEL && INVARIANTS) */
 514
 515 #define LIST_CONCAT(head1, head2, type, field) do {                           \
 516         QUEUE_TYPEOF(type) *curelm = LIST_FIRST(head1);                       \
 517         if (curelm == NULL) {                                                 \
 518                 if ((LIST_FIRST(head1) = LIST_FIRST(head2)) != NULL) {        \
 519                         LIST_FIRST(head2)->field.le_prev =                    \
 520                             &LIST_FIRST((head1));                             \
 521                         LIST_INIT(head2);                                     \
 522                 }                                                             \
 523         } else if (LIST_FIRST(head2) != NULL) {                               \
 524                 while (LIST_NEXT(curelm, field) != NULL)                      \
 525                         curelm = LIST_NEXT(curelm, field);                    \
 526                 LIST_NEXT(curelm, field) = LIST_FIRST(head2);                 \
 527                 LIST_FIRST(head2)->field.le_prev = &LIST_NEXT(curelm, field); \
 528                 LIST_INIT(head2);                                             \
 529         }                                                                     \
 530 } while (0)
 531
 532 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 533
 534 #define LIST_FIRST(head)        ((head)->lh_first)
 535
 536 #define LIST_FOREACH(var, head, field)                                  \
 537         for ((var) = LIST_FIRST((head));                                \
 538             (var);                                                      \
 539             (var) = LIST_NEXT((var), field))
 540
 541 #define LIST_FOREACH_FROM(var, head, field)                             \
 542         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 543             (var);                                                      \
 544             (var) = LIST_NEXT((var), field))
 545
 546 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 547         for ((var) = LIST_FIRST((head));                                \
 548             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 549             (var) = (tvar))
 550
 551 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
 552         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 553             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 554             (var) = (tvar))
 555
 556 #define LIST_INIT(head) do {                                            \
 557         LIST_FIRST((head)) = NULL;                                      \
 558 } while (0)
 559
 560 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 561         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 562         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 563                 LIST_NEXT((listelm), field)->field.le_prev =            \
 564                     &LIST_NEXT((elm), field);                           \
 565         LIST_NEXT((listelm), field) = (elm);                            \
 566         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 567 } while (0)
 568
 569 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 570         QMD_LIST_CHECK_PREV(listelm, field);                            \
 571         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 572         LIST_NEXT((elm), field) = (listelm);                            \
 573         *(listelm)->field.le_prev = (elm);                              \
 574         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 575 } while (0)
 576
 577 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 578         QMD_LIST_CHECK_HEAD((head), field);                             \
 579         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 580                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 581         LIST_FIRST((head)) = (elm);                                     \
 582         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 583 } while (0)
 584
 585 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 586
 587 #define LIST_PREV(elm, head, type, field)                       \
 588         ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
 589             __containerof((elm)->field.le_prev,                 \
 590             QUEUE_TYPEOF(type), field.le_next))
 591
 592 #define LIST_REMOVE(elm, field) do {                                    \
 593         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 594         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 595         QMD_LIST_CHECK_NEXT(elm, field);                                \
 596         QMD_LIST_CHECK_PREV(elm, field);                                \
 597         if (LIST_NEXT((elm), field) != NULL)                            \
 598                 LIST_NEXT((elm), field)->field.le_prev =                \
 599                     (elm)->field.le_prev;                               \
 600         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 601         TRASHIT(*oldnext);                                              \
 602         TRASHIT(*oldprev);                                              \
 603 } while (0)
 604
 605 #define LIST_SWAP(head1, head2, type, field) do {                       \
 606         QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
 607         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 608         LIST_FIRST((head2)) = swap_tmp;                                 \
 609         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 610                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 611         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 612                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 613 } while (0)
 614
 615 /*
 616  * Tail queue declarations.
 617  */
 618 #define TAILQ_HEAD(name, type)                                          \
 619 struct name {                                                           \
 620         struct type *tqh_first; /* first element */                     \
 621         struct type **tqh_last; /* addr of last next element */         \
 622         TRACEBUF                                                        \
 623 }
 624
 625 #define TAILQ_CLASS_HEAD(name, type)                                    \
 626 struct name {                                                           \
 627         class type *tqh_first;  /* first element */                     \
 628         class type **tqh_last;  /* addr of last next element */         \
 629         TRACEBUF                                                        \
 630 }
 631
 632 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 633         { NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }
 634
 635 #define TAILQ_ENTRY(type)                                               \
 636 struct {                                                                \
 637         struct type *tqe_next;  /* next element */                      \
 638         struct type **tqe_prev; /* address of previous next element */  \
 639         TRACEBUF                                                        \
 640 }
 641
 642 #define TAILQ_CLASS_ENTRY(type)                                         \
 643 struct {                                                                \
 644         class type *tqe_next;   /* next element */                      \
 645         class type **tqe_prev;  /* address of previous next element */  \
 646         TRACEBUF                                                        \
 647 }
 648
 649 /*
 650  * Tail queue functions.
 651  */
 652 #if (defined(_KERNEL) && defined(INVARIANTS))
 653 /*
 654  * QMD_TAILQ_CHECK_HEAD(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
 655  *
 656  * If the tailq is non-empty, validates that the first element of the tailq
 657  * points back at 'head.'
 658  */
 659 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 660         if (!TAILQ_EMPTY(head) &&                                       \
 661             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 662              &TAILQ_FIRST((head)))                                      \
 663                 panic("Bad tailq head %p first->prev != head", (head)); \
 664 } while (0)
 665
 666 /*
 667  * QMD_TAILQ_CHECK_TAIL(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
 668  *
 669  * Validates that the tail of the tailq is a pointer to pointer to NULL.
 670  */
 671 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 672         if (*(head)->tqh_last != NULL)                                  \
 673                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 674 } while (0)
 675
 676 /*
 677  * QMD_TAILQ_CHECK_NEXT(TYPE *elm, TAILQ_ENTRY NAME)
 678  *
 679  * If an element follows 'elm' in the tailq, validates that the next element
 680  * points back at 'elm.'
 681  */
 682 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 683         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 684             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 685              &((elm)->field.tqe_next))                                  \
 686                 panic("Bad link elm %p next->prev != elm", (elm));      \
 687 } while (0)
 688
 689 /*
 690  * QMD_TAILQ_CHECK_PREV(TYPE *elm, TAILQ_ENTRY NAME)
 691  *
 692  * Validates that the previous element (or head of the tailq) points to 'elm.'
 693  */
 694 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 695         if (*(elm)->field.tqe_prev != (elm))                            \
 696                 panic("Bad link elm %p prev->next != elm", (elm));      \
 697 } while (0)
 698 #else
 699 #define QMD_TAILQ_CHECK_HEAD(head, field)
 700 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 701 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 702 #define QMD_TAILQ_CHECK_PREV(elm, field)
 703 #endif /* (_KERNEL && INVARIANTS) */
 704
 705 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 706         if (!TAILQ_EMPTY(head2)) {                                      \
 707                 *(head1)->tqh_last = (head2)->tqh_first;                \
 708                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 709                 (head1)->tqh_last = (head2)->tqh_last;                  \
 710                 TAILQ_INIT((head2));                                    \
 711                 QMD_TRACE_HEAD(head1);                                  \
 712                 QMD_TRACE_HEAD(head2);                                  \
 713         }                                                               \
 714 } while (0)
 715
 716 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 717
 718 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 719
 720 #define TAILQ_FOREACH(var, head, field)                                 \
 721         for ((var) = TAILQ_FIRST((head));                               \
 722             (var);                                                      \
 723             (var) = TAILQ_NEXT((var), field))
 724
 725 #define TAILQ_FOREACH_FROM(var, head, field)                            \
 726         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 727             (var);                                                      \
 728             (var) = TAILQ_NEXT((var), field))
 729
 730 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 731         for ((var) = TAILQ_FIRST((head));                               \
 732             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 733             (var) = (tvar))
 734
 735 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 736         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 737             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 738             (var) = (tvar))
 739
 740 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 741         for ((var) = TAILQ_LAST((head), headname);                      \
 742             (var);                                                      \
 743             (var) = TAILQ_PREV((var), headname, field))
 744
 745 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)          \
 746         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 747             (var);                                                      \
 748             (var) = TAILQ_PREV((var), headname, field))
 749
 750 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 751         for ((var) = TAILQ_LAST((head), headname);                      \
 752             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 753             (var) = (tvar))
 754
 755 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
 756         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 757             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 758             (var) = (tvar))
 759
 760 #define TAILQ_INIT(head) do {                                           \
 761         TAILQ_FIRST((head)) = NULL;                                     \
 762         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 763         QMD_TRACE_HEAD(head);                                           \
 764 } while (0)
 765
 766 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 767         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 768         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 769                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 770                     &TAILQ_NEXT((elm), field);                          \
 771         else {                                                          \
 772                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 773                 QMD_TRACE_HEAD(head);                                   \
 774         }                                                               \
 775         TAILQ_NEXT((listelm), field) = (elm);                           \
 776         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 777         QMD_TRACE_ELEM(&(elm)->field);                                  \
 778         QMD_TRACE_ELEM(&(listelm)->field);                              \
 779 } while (0)
 780
 781 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 782         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 783         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 784         TAILQ_NEXT((elm), field) = (listelm);                           \
 785         *(listelm)->field.tqe_prev = (elm);                             \
 786         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 787         QMD_TRACE_ELEM(&(elm)->field);                                  \
 788         QMD_TRACE_ELEM(&(listelm)->field);                              \
 789 } while (0)
 790
 791 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 792         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 793         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 794                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 795                     &TAILQ_NEXT((elm), field);                          \
 796         else                                                            \
 797                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 798         TAILQ_FIRST((head)) = (elm);                                    \
 799         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 800         QMD_TRACE_HEAD(head);                                           \
 801         QMD_TRACE_ELEM(&(elm)->field);                                  \
 802 } while (0)
 803
 804 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 805         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 806         TAILQ_NEXT((elm), field) = NULL;                                \
 807         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 808         *(head)->tqh_last = (elm);                                      \
 809         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 810         QMD_TRACE_HEAD(head);                                           \
 811         QMD_TRACE_ELEM(&(elm)->field);                                  \
 812 } while (0)
 813
 814 #define TAILQ_LAST(head, headname)                                      \
 815         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 816
 817 /*
 818  * The FAST function is fast in that it causes no data access other
 819  * then the access to the head. The standard LAST function above
 820  * will cause a data access of both the element you want and
 821  * the previous element. FAST is very useful for instances when
 822  * you may want to prefetch the last data element.
 823  */
 824 #define TAILQ_LAST_FAST(head, type, field)                      \
 825     (TAILQ_EMPTY(head) ? NULL : __containerof((head)->tqh_last, QUEUE_TYPEOF(type), field.tqe_next))
 826
 827 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 828
 829 #define TAILQ_PREV(elm, headname, field)                                \
 830         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 831
 832 #define TAILQ_PREV_FAST(elm, head, type, field)                         \
 833     ((elm)->field.tqe_prev == &(head)->tqh_first ? NULL :               \
 834      __containerof((elm)->field.tqe_prev, QUEUE_TYPEOF(type), field.tqe_next))
 835
 836 #define TAILQ_REMOVE(head, elm, field) do {                             \
 837         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 838         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 839         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 840         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 841         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 842                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 843                     (elm)->field.tqe_prev;                              \
 844         else {                                                          \
 845                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 846                 QMD_TRACE_HEAD(head);                                   \
 847         }                                                               \
 848         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 849         TRASHIT(*oldnext);                                              \
 850         TRASHIT(*oldprev);                                              \
 851         QMD_TRACE_ELEM(&(elm)->field);                                  \
 852 } while (0)
 853
 854 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 855         QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
 856         QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
 857         (head1)->tqh_first = (head2)->tqh_first;                        \
 858         (head1)->tqh_last = (head2)->tqh_last;                          \
 859         (head2)->tqh_first = swap_first;                                \
 860         (head2)->tqh_last = swap_last;                                  \
 861         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 862                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 863         else                                                            \
 864                 (head1)->tqh_last = &(head1)->tqh_first;                \
 865         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 866                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 867         else                                                            \
 868                 (head2)->tqh_last = &(head2)->tqh_first;                \
 869 } while (0)
 870
 871 #endif /* !_SYS_QUEUE_H_ */