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 TRASHIT(x)              do {(x) = (void *)-1;} while (0)
 159 #define QMD_IS_TRASHED(x)       ((x) == (void *)(intptr_t)-1)
 160 #else   /* !QUEUE_MACRO_DEBUG_TRASH */
 161 #define TRASHIT(x)
 162 #define QMD_IS_TRASHED(x)       0
 163 #endif  /* QUEUE_MACRO_DEBUG_TRASH */
 164
 165 #if defined(QUEUE_MACRO_DEBUG_TRACE) || defined(QUEUE_MACRO_DEBUG_TRASH)
 166 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 167 #else   /* !QUEUE_MACRO_DEBUG_TRACE && !QUEUE_MACRO_DEBUG_TRASH */
 168 #define QMD_SAVELINK(name, link)
 169 #endif  /* QUEUE_MACRO_DEBUG_TRACE || QUEUE_MACRO_DEBUG_TRASH */
 170
 171 #ifdef __cplusplus
 172 /*
 173  * In C++ there can be structure lists and class lists:
 174  */
 175 #define QUEUE_TYPEOF(type) type
 176 #else
 177 #define QUEUE_TYPEOF(type) struct type
 178 #endif
 179
 180 /*
 181  * Singly-linked List declarations.
 182  */
 183 #define SLIST_HEAD(name, type)                                          \
 184 struct name {                                                           \
 185         struct type *slh_first; /* first element */                     \
 186 }
 187
 188 #define SLIST_CLASS_HEAD(name, type)                                    \
 189 struct name {                                                           \
 190         class type *slh_first;  /* first element */                     \
 191 }
 192
 193 #define SLIST_HEAD_INITIALIZER(head)                                    \
 194         { NULL }
 195
 196 #define SLIST_ENTRY(type)                                               \
 197 struct {                                                                \
 198         struct type *sle_next;  /* next element */                      \
 199 }
 200
 201 #define SLIST_CLASS_ENTRY(type)                                         \
 202 struct {                                                                \
 203         class type *sle_next;           /* next element */              \
 204 }
 205
 206 /*
 207  * Singly-linked List functions.
 208  */
 209 #if (defined(_KERNEL) && defined(INVARIANTS))
 210 #define QMD_SLIST_CHECK_PREVPTR(prevp, elm) do {                        \
 211         if (*(prevp) != (elm))                                          \
 212                 panic("Bad prevptr *(%p) == %p != %p",                  \
 213                     (prevp), *(prevp), (elm));                          \
 214 } while (0)
 215 #else
 216 #define QMD_SLIST_CHECK_PREVPTR(prevp, elm)
 217 #endif
 218
 219 #define SLIST_CONCAT(head1, head2, type, field) do {                    \
 220         QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head1);                \
 221         if (curelm == NULL) {                                           \
 222                 if ((SLIST_FIRST(head1) = SLIST_FIRST(head2)) != NULL)  \
 223                         SLIST_INIT(head2);                              \
 224         } else if (SLIST_FIRST(head2) != NULL) {                        \
 225                 while (SLIST_NEXT(curelm, field) != NULL)               \
 226                         curelm = SLIST_NEXT(curelm, field);             \
 227                 SLIST_NEXT(curelm, field) = SLIST_FIRST(head2);         \
 228                 SLIST_INIT(head2);                                      \
 229         }                                                               \
 230 } while (0)
 231
 232 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 233
 234 #define SLIST_FIRST(head)       ((head)->slh_first)
 235
 236 #define SLIST_FOREACH(var, head, field)                                 \
 237         for ((var) = SLIST_FIRST((head));                               \
 238             (var);                                                      \
 239             (var) = SLIST_NEXT((var), field))
 240
 241 #define SLIST_FOREACH_FROM(var, head, field)                            \
 242         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 243             (var);                                                      \
 244             (var) = SLIST_NEXT((var), field))
 245
 246 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 247         for ((var) = SLIST_FIRST((head));                               \
 248             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 249             (var) = (tvar))
 250
 251 #define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 252         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 253             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 254             (var) = (tvar))
 255
 256 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 257         for ((varp) = &SLIST_FIRST((head));                             \
 258             ((var) = *(varp)) != NULL;                                  \
 259             (varp) = &SLIST_NEXT((var), field))
 260
 261 #define SLIST_INIT(head) do {                                           \
 262         SLIST_FIRST((head)) = NULL;                                     \
 263 } while (0)
 264
 265 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 266         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 267         SLIST_NEXT((slistelm), field) = (elm);                          \
 268 } while (0)
 269
 270 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 271         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 272         SLIST_FIRST((head)) = (elm);                                    \
 273 } while (0)
 274
 275 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 276
 277 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 278         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
 279         if (SLIST_FIRST((head)) == (elm)) {                             \
 280                 SLIST_REMOVE_HEAD((head), field);                       \
 281         }                                                               \
 282         else {                                                          \
 283                 QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head);         \
 284                 while (SLIST_NEXT(curelm, field) != (elm))              \
 285                         curelm = SLIST_NEXT(curelm, field);             \
 286                 SLIST_REMOVE_AFTER(curelm, field);                      \
 287         }                                                               \
 288         TRASHIT(*oldnext);                                              \
 289 } while (0)
 290
 291 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 292         SLIST_NEXT(elm, field) =                                        \
 293             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 294 } while (0)
 295
 296 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 297         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 298 } while (0)
 299
 300 #define SLIST_REMOVE_PREVPTR(prevp, elm, field) do {                    \
 301         QMD_SLIST_CHECK_PREVPTR(prevp, elm);                            \
 302         *(prevp) = SLIST_NEXT(elm, field);                              \
 303         TRASHIT((elm)->field.sle_next);                                 \
 304 } while (0)
 305
 306 #define SLIST_SWAP(head1, head2, type) do {                             \
 307         QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
 308         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
 309         SLIST_FIRST(head2) = swap_first;                                \
 310 } while (0)
 311
 312 /*
 313  * Singly-linked Tail queue declarations.
 314  */
 315 #define STAILQ_HEAD(name, type)                                         \
 316 struct name {                                                           \
 317         struct type *stqh_first;/* first element */                     \
 318         struct type **stqh_last;/* addr of last next element */         \
 319 }
 320
 321 #define STAILQ_CLASS_HEAD(name, type)                                   \
 322 struct name {                                                           \
 323         class type *stqh_first; /* first element */                     \
 324         class type **stqh_last; /* addr of last next element */         \
 325 }
 326
 327 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 328         { NULL, &(head).stqh_first }
 329
 330 #define STAILQ_ENTRY(type)                                              \
 331 struct {                                                                \
 332         struct type *stqe_next; /* next element */                      \
 333 }
 334
 335 #define STAILQ_CLASS_ENTRY(type)                                        \
 336 struct {                                                                \
 337         class type *stqe_next;  /* next element */                      \
 338 }
 339
 340 /*
 341  * Singly-linked Tail queue functions.
 342  */
 343 #define STAILQ_CONCAT(head1, head2) do {                                \
 344         if (!STAILQ_EMPTY((head2))) {                                   \
 345                 *(head1)->stqh_last = (head2)->stqh_first;              \
 346                 (head1)->stqh_last = (head2)->stqh_last;                \
 347                 STAILQ_INIT((head2));                                   \
 348         }                                                               \
 349 } while (0)
 350
 351 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 352
 353 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 354
 355 #define STAILQ_FOREACH(var, head, field)                                \
 356         for((var) = STAILQ_FIRST((head));                               \
 357            (var);                                                       \
 358            (var) = STAILQ_NEXT((var), field))
 359
 360 #define STAILQ_FOREACH_FROM(var, head, field)                           \
 361         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 362            (var);                                                       \
 363            (var) = STAILQ_NEXT((var), field))
 364
 365 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 366         for ((var) = STAILQ_FIRST((head));                              \
 367             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 368             (var) = (tvar))
 369
 370 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
 371         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 372             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 373             (var) = (tvar))
 374
 375 #define STAILQ_INIT(head) do {                                          \
 376         STAILQ_FIRST((head)) = NULL;                                    \
 377         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 378 } while (0)
 379
 380 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 381         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 382                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 383         STAILQ_NEXT((tqelm), field) = (elm);                            \
 384 } while (0)
 385
 386 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 387         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 388                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 389         STAILQ_FIRST((head)) = (elm);                                   \
 390 } while (0)
 391
 392 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 393         STAILQ_NEXT((elm), field) = NULL;                               \
 394         *(head)->stqh_last = (elm);                                     \
 395         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 396 } while (0)
 397
 398 #define STAILQ_LAST(head, type, field)                          \
 399         (STAILQ_EMPTY((head)) ? NULL :                          \
 400             __containerof((head)->stqh_last,                    \
 401             QUEUE_TYPEOF(type), field.stqe_next))
 402
 403 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 404
 405 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 406         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 407         if (STAILQ_FIRST((head)) == (elm)) {                            \
 408                 STAILQ_REMOVE_HEAD((head), field);                      \
 409         }                                                               \
 410         else {                                                          \
 411                 QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
 412                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 413                         curelm = STAILQ_NEXT(curelm, field);            \
 414                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 415         }                                                               \
 416         TRASHIT(*oldnext);                                              \
 417 } while (0)
 418
 419 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 420         if ((STAILQ_NEXT(elm, field) =                                  \
 421              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 422                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 423 } while (0)
 424
 425 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 426         if ((STAILQ_FIRST((head)) =                                     \
 427              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 428                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 429 } while (0)
 430
 431 #define STAILQ_SWAP(head1, head2, type) do {                            \
 432         QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
 433         QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
 434         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 435         (head1)->stqh_last = (head2)->stqh_last;                        \
 436         STAILQ_FIRST(head2) = swap_first;                               \
 437         (head2)->stqh_last = swap_last;                                 \
 438         if (STAILQ_EMPTY(head1))                                        \
 439                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 440         if (STAILQ_EMPTY(head2))                                        \
 441                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 442 } while (0)
 443
 444
 445 /*
 446  * List declarations.
 447  */
 448 #define LIST_HEAD(name, type)                                           \
 449 struct name {                                                           \
 450         struct type *lh_first;  /* first element */                     \
 451 }
 452
 453 #define LIST_CLASS_HEAD(name, type)                                     \
 454 struct name {                                                           \
 455         class type *lh_first;   /* first element */                     \
 456 }
 457
 458 #define LIST_HEAD_INITIALIZER(head)                                     \
 459         { NULL }
 460
 461 #define LIST_ENTRY(type)                                                \
 462 struct {                                                                \
 463         struct type *le_next;   /* next element */                      \
 464         struct type **le_prev;  /* address of previous next element */  \
 465 }
 466
 467 #define LIST_CLASS_ENTRY(type)                                          \
 468 struct {                                                                \
 469         class type *le_next;    /* next element */                      \
 470         class type **le_prev;   /* address of previous next element */  \
 471 }
 472
 473 /*
 474  * List functions.
 475  */
 476
 477 #if (defined(_KERNEL) && defined(INVARIANTS))
 478 /*
 479  * QMD_LIST_CHECK_HEAD(LIST_HEAD *head, LIST_ENTRY NAME)
 480  *
 481  * If the list is non-empty, validates that the first element of the list
 482  * points back at 'head.'
 483  */
 484 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 485         if (LIST_FIRST((head)) != NULL &&                               \
 486             LIST_FIRST((head))->field.le_prev !=                        \
 487              &LIST_FIRST((head)))                                       \
 488                 panic("Bad list head %p first->prev != head", (head));  \
 489 } while (0)
 490
 491 /*
 492  * QMD_LIST_CHECK_NEXT(TYPE *elm, LIST_ENTRY NAME)
 493  *
 494  * If an element follows 'elm' in the list, validates that the next element
 495  * points back at 'elm.'
 496  */
 497 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 498         if (LIST_NEXT((elm), field) != NULL &&                          \
 499             LIST_NEXT((elm), field)->field.le_prev !=                   \
 500              &((elm)->field.le_next))                                   \
 501                 panic("Bad link elm %p next->prev != elm", (elm));      \
 502 } while (0)
 503
 504 /*
 505  * QMD_LIST_CHECK_PREV(TYPE *elm, LIST_ENTRY NAME)
 506  *
 507  * Validates that the previous element (or head of the list) points to 'elm.'
 508  */
 509 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 510         if (*(elm)->field.le_prev != (elm))                             \
 511                 panic("Bad link elm %p prev->next != elm", (elm));      \
 512 } while (0)
 513 #else
 514 #define QMD_LIST_CHECK_HEAD(head, field)
 515 #define QMD_LIST_CHECK_NEXT(elm, field)
 516 #define QMD_LIST_CHECK_PREV(elm, field)
 517 #endif /* (_KERNEL && INVARIANTS) */
 518
 519 #define LIST_CONCAT(head1, head2, type, field) do {                           \
 520         QUEUE_TYPEOF(type) *curelm = LIST_FIRST(head1);                       \
 521         if (curelm == NULL) {                                                 \
 522                 if ((LIST_FIRST(head1) = LIST_FIRST(head2)) != NULL) {        \
 523                         LIST_FIRST(head2)->field.le_prev =                    \
 524                             &LIST_FIRST((head1));                             \
 525                         LIST_INIT(head2);                                     \
 526                 }                                                             \
 527         } else if (LIST_FIRST(head2) != NULL) {                               \
 528                 while (LIST_NEXT(curelm, field) != NULL)                      \
 529                         curelm = LIST_NEXT(curelm, field);                    \
 530                 LIST_NEXT(curelm, field) = LIST_FIRST(head2);                 \
 531                 LIST_FIRST(head2)->field.le_prev = &LIST_NEXT(curelm, field); \
 532                 LIST_INIT(head2);                                             \
 533         }                                                                     \
 534 } while (0)
 535
 536 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 537
 538 #define LIST_FIRST(head)        ((head)->lh_first)
 539
 540 #define LIST_FOREACH(var, head, field)                                  \
 541         for ((var) = LIST_FIRST((head));                                \
 542             (var);                                                      \
 543             (var) = LIST_NEXT((var), field))
 544
 545 #define LIST_FOREACH_FROM(var, head, field)                             \
 546         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 547             (var);                                                      \
 548             (var) = LIST_NEXT((var), field))
 549
 550 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 551         for ((var) = LIST_FIRST((head));                                \
 552             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 553             (var) = (tvar))
 554
 555 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
 556         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 557             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 558             (var) = (tvar))
 559
 560 #define LIST_INIT(head) do {                                            \
 561         LIST_FIRST((head)) = NULL;                                      \
 562 } while (0)
 563
 564 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 565         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 566         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 567                 LIST_NEXT((listelm), field)->field.le_prev =            \
 568                     &LIST_NEXT((elm), field);                           \
 569         LIST_NEXT((listelm), field) = (elm);                            \
 570         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 571 } while (0)
 572
 573 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 574         QMD_LIST_CHECK_PREV(listelm, field);                            \
 575         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 576         LIST_NEXT((elm), field) = (listelm);                            \
 577         *(listelm)->field.le_prev = (elm);                              \
 578         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 579 } while (0)
 580
 581 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 582         QMD_LIST_CHECK_HEAD((head), field);                             \
 583         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 584                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 585         LIST_FIRST((head)) = (elm);                                     \
 586         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 587 } while (0)
 588
 589 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 590
 591 #define LIST_PREV(elm, head, type, field)                       \
 592         ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
 593             __containerof((elm)->field.le_prev,                 \
 594             QUEUE_TYPEOF(type), field.le_next))
 595
 596 #define LIST_REMOVE(elm, field) do {                                    \
 597         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 598         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 599         QMD_LIST_CHECK_NEXT(elm, field);                                \
 600         QMD_LIST_CHECK_PREV(elm, field);                                \
 601         if (LIST_NEXT((elm), field) != NULL)                            \
 602                 LIST_NEXT((elm), field)->field.le_prev =                \
 603                     (elm)->field.le_prev;                               \
 604         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 605         TRASHIT(*oldnext);                                              \
 606         TRASHIT(*oldprev);                                              \
 607 } while (0)
 608
 609 #define LIST_SWAP(head1, head2, type, field) do {                       \
 610         QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
 611         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 612         LIST_FIRST((head2)) = swap_tmp;                                 \
 613         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 614                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 615         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 616                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 617 } while (0)
 618
 619 /*
 620  * Tail queue declarations.
 621  */
 622 #define TAILQ_HEAD(name, type)                                          \
 623 struct name {                                                           \
 624         struct type *tqh_first; /* first element */                     \
 625         struct type **tqh_last; /* addr of last next element */         \
 626         TRACEBUF                                                        \
 627 }
 628
 629 #define TAILQ_CLASS_HEAD(name, type)                                    \
 630 struct name {                                                           \
 631         class type *tqh_first;  /* first element */                     \
 632         class type **tqh_last;  /* addr of last next element */         \
 633         TRACEBUF                                                        \
 634 }
 635
 636 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 637         { NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }
 638
 639 #define TAILQ_ENTRY(type)                                               \
 640 struct {                                                                \
 641         struct type *tqe_next;  /* next element */                      \
 642         struct type **tqe_prev; /* address of previous next element */  \
 643         TRACEBUF                                                        \
 644 }
 645
 646 #define TAILQ_CLASS_ENTRY(type)                                         \
 647 struct {                                                                \
 648         class type *tqe_next;   /* next element */                      \
 649         class type **tqe_prev;  /* address of previous next element */  \
 650         TRACEBUF                                                        \
 651 }
 652
 653 /*
 654  * Tail queue functions.
 655  */
 656 #if (defined(_KERNEL) && defined(INVARIANTS))
 657 /*
 658  * QMD_TAILQ_CHECK_HEAD(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
 659  *
 660  * If the tailq is non-empty, validates that the first element of the tailq
 661  * points back at 'head.'
 662  */
 663 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 664         if (!TAILQ_EMPTY(head) &&                                       \
 665             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 666              &TAILQ_FIRST((head)))                                      \
 667                 panic("Bad tailq head %p first->prev != head", (head)); \
 668 } while (0)
 669
 670 /*
 671  * QMD_TAILQ_CHECK_TAIL(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
 672  *
 673  * Validates that the tail of the tailq is a pointer to pointer to NULL.
 674  */
 675 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 676         if (*(head)->tqh_last != NULL)                                  \
 677                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 678 } while (0)
 679
 680 /*
 681  * QMD_TAILQ_CHECK_NEXT(TYPE *elm, TAILQ_ENTRY NAME)
 682  *
 683  * If an element follows 'elm' in the tailq, validates that the next element
 684  * points back at 'elm.'
 685  */
 686 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 687         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 688             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 689              &((elm)->field.tqe_next))                                  \
 690                 panic("Bad link elm %p next->prev != elm", (elm));      \
 691 } while (0)
 692
 693 /*
 694  * QMD_TAILQ_CHECK_PREV(TYPE *elm, TAILQ_ENTRY NAME)
 695  *
 696  * Validates that the previous element (or head of the tailq) points to 'elm.'
 697  */
 698 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 699         if (*(elm)->field.tqe_prev != (elm))                            \
 700                 panic("Bad link elm %p prev->next != elm", (elm));      \
 701 } while (0)
 702 #else
 703 #define QMD_TAILQ_CHECK_HEAD(head, field)
 704 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 705 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 706 #define QMD_TAILQ_CHECK_PREV(elm, field)
 707 #endif /* (_KERNEL && INVARIANTS) */
 708
 709 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 710         if (!TAILQ_EMPTY(head2)) {                                      \
 711                 *(head1)->tqh_last = (head2)->tqh_first;                \
 712                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 713                 (head1)->tqh_last = (head2)->tqh_last;                  \
 714                 TAILQ_INIT((head2));                                    \
 715                 QMD_TRACE_HEAD(head1);                                  \
 716                 QMD_TRACE_HEAD(head2);                                  \
 717         }                                                               \
 718 } while (0)
 719
 720 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 721
 722 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 723
 724 #define TAILQ_FOREACH(var, head, field)                                 \
 725         for ((var) = TAILQ_FIRST((head));                               \
 726             (var);                                                      \
 727             (var) = TAILQ_NEXT((var), field))
 728
 729 #define TAILQ_FOREACH_FROM(var, head, field)                            \
 730         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 731             (var);                                                      \
 732             (var) = TAILQ_NEXT((var), field))
 733
 734 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 735         for ((var) = TAILQ_FIRST((head));                               \
 736             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 737             (var) = (tvar))
 738
 739 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 740         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 741             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 742             (var) = (tvar))
 743
 744 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 745         for ((var) = TAILQ_LAST((head), headname);                      \
 746             (var);                                                      \
 747             (var) = TAILQ_PREV((var), headname, field))
 748
 749 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)          \
 750         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 751             (var);                                                      \
 752             (var) = TAILQ_PREV((var), headname, field))
 753
 754 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 755         for ((var) = TAILQ_LAST((head), headname);                      \
 756             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 757             (var) = (tvar))
 758
 759 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
 760         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 761             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 762             (var) = (tvar))
 763
 764 #define TAILQ_INIT(head) do {                                           \
 765         TAILQ_FIRST((head)) = NULL;                                     \
 766         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 767         QMD_TRACE_HEAD(head);                                           \
 768 } while (0)
 769
 770 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 771         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 772         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 773                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 774                     &TAILQ_NEXT((elm), field);                          \
 775         else {                                                          \
 776                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 777                 QMD_TRACE_HEAD(head);                                   \
 778         }                                                               \
 779         TAILQ_NEXT((listelm), field) = (elm);                           \
 780         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 781         QMD_TRACE_ELEM(&(elm)->field);                                  \
 782         QMD_TRACE_ELEM(&(listelm)->field);                              \
 783 } while (0)
 784
 785 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 786         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 787         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 788         TAILQ_NEXT((elm), field) = (listelm);                           \
 789         *(listelm)->field.tqe_prev = (elm);                             \
 790         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 791         QMD_TRACE_ELEM(&(elm)->field);                                  \
 792         QMD_TRACE_ELEM(&(listelm)->field);                              \
 793 } while (0)
 794
 795 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 796         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 797         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 798                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 799                     &TAILQ_NEXT((elm), field);                          \
 800         else                                                            \
 801                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 802         TAILQ_FIRST((head)) = (elm);                                    \
 803         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 804         QMD_TRACE_HEAD(head);                                           \
 805         QMD_TRACE_ELEM(&(elm)->field);                                  \
 806 } while (0)
 807
 808 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 809         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 810         TAILQ_NEXT((elm), field) = NULL;                                \
 811         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 812         *(head)->tqh_last = (elm);                                      \
 813         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 814         QMD_TRACE_HEAD(head);                                           \
 815         QMD_TRACE_ELEM(&(elm)->field);                                  \
 816 } while (0)
 817
 818 #define TAILQ_LAST(head, headname)                                      \
 819         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 820
 821 /*
 822  * The FAST function is fast in that it causes no data access other
 823  * then the access to the head. The standard LAST function above
 824  * will cause a data access of both the element you want and
 825  * the previous element. FAST is very useful for instances when
 826  * you may want to prefetch the last data element.
 827  */
 828 #define TAILQ_LAST_FAST(head, type, field)                      \
 829     (TAILQ_EMPTY(head) ? NULL : __containerof((head)->tqh_last, QUEUE_TYPEOF(type), field.tqe_next))
 830
 831 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 832
 833 #define TAILQ_PREV(elm, headname, field)                                \
 834         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 835
 836 #define TAILQ_PREV_FAST(elm, head, type, field)                         \
 837     ((elm)->field.tqe_prev == &(head)->tqh_first ? NULL :               \
 838      __containerof((elm)->field.tqe_prev, QUEUE_TYPEOF(type), field.tqe_next))
 839
 840 #define TAILQ_REMOVE(head, elm, field) do {                             \
 841         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 842         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 843         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 844         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 845         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 846                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 847                     (elm)->field.tqe_prev;                              \
 848         else {                                                          \
 849                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 850                 QMD_TRACE_HEAD(head);                                   \
 851         }                                                               \
 852         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 853         TRASHIT(*oldnext);                                              \
 854         TRASHIT(*oldprev);                                              \
 855         QMD_TRACE_ELEM(&(elm)->field);                                  \
 856 } while (0)
 857
 858 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 859         QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
 860         QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
 861         (head1)->tqh_first = (head2)->tqh_first;                        \
 862         (head1)->tqh_last = (head2)->tqh_last;                          \
 863         (head2)->tqh_first = swap_first;                                \
 864         (head2)->tqh_last = swap_last;                                  \
 865         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 866                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 867         else                                                            \
 868                 (head1)->tqh_last = &(head1)->tqh_first;                \
 869         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 870                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 871         else                                                            \
 872                 (head2)->tqh_last = &(head2)->tqh_first;                \
 873 } while (0)
 874
 875 #endif /* !_SYS_QUEUE_H_ */