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  * _END                         +       +       +       +
  95  * _FIRST                       +       +       +       +
  96  * _NEXT                        +       +       +       +
  97  * _PREV                        -       +       -       +
  98  * _LAST                        -       -       +       +
  99  * _LAST_FAST                   -       -       -       +
 100  * _FOREACH                     +       +       +       +
 101  * _FOREACH_FROM                +       +       +       +
 102  * _FOREACH_SAFE                +       +       +       +
 103  * _FOREACH_FROM_SAFE           +       +       +       +
 104  * _FOREACH_REVERSE             -       -       -       +
 105  * _FOREACH_REVERSE_FROM        -       -       -       +
 106  * _FOREACH_REVERSE_SAFE        -       -       -       +
 107  * _FOREACH_REVERSE_FROM_SAFE   -       -       -       +
 108  * _INSERT_HEAD                 +       +       +       +
 109  * _INSERT_BEFORE               -       +       -       +
 110  * _INSERT_AFTER                +       +       +       +
 111  * _INSERT_TAIL                 -       -       +       +
 112  * _CONCAT                      s       s       +       +
 113  * _REMOVE_AFTER                +       -       +       -
 114  * _REMOVE_HEAD                 +       -       +       -
 115  * _REMOVE                      s       +       s       +
 116  * _SWAP                        +       +       +       +
 117  *
 118  */
 119 #ifdef QUEUE_MACRO_DEBUG
 120 #warn Use QUEUE_MACRO_DEBUG_TRACE and/or QUEUE_MACRO_DEBUG_TRASH
 121 #define QUEUE_MACRO_DEBUG_TRACE
 122 #define QUEUE_MACRO_DEBUG_TRASH
 123 #endif
 124
 125 #ifdef QUEUE_MACRO_DEBUG_TRACE
 126 /* Store the last 2 places the queue element or head was altered */
 127 struct qm_trace {
 128         unsigned long    lastline;
 129         unsigned long    prevline;
 130         const char      *lastfile;
 131         const char      *prevfile;
 132 };
 133
 134 #define TRACEBUF        struct qm_trace trace;
 135 #define TRACEBUF_INITIALIZER    { __LINE__, 0, __FILE__, NULL } ,
 136
 137 #define QMD_TRACE_HEAD(head) do {                                       \
 138         (head)->trace.prevline = (head)->trace.lastline;                \
 139         (head)->trace.prevfile = (head)->trace.lastfile;                \
 140         (head)->trace.lastline = __LINE__;                              \
 141         (head)->trace.lastfile = __FILE__;                              \
 142 } while (0)
 143
 144 #define QMD_TRACE_ELEM(elem) do {                                       \
 145         (elem)->trace.prevline = (elem)->trace.lastline;                \
 146         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
 147         (elem)->trace.lastline = __LINE__;                              \
 148         (elem)->trace.lastfile = __FILE__;                              \
 149 } while (0)
 150
 151 #else   /* !QUEUE_MACRO_DEBUG_TRACE */
 152 #define QMD_TRACE_ELEM(elem)
 153 #define QMD_TRACE_HEAD(head)
 154 #define TRACEBUF
 155 #define TRACEBUF_INITIALIZER
 156 #endif  /* QUEUE_MACRO_DEBUG_TRACE */
 157
 158 #ifdef QUEUE_MACRO_DEBUG_TRASH
 159 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
 160 #define TRASHIT(x)              do {(x) = (void *)-1;} while (0)
 161 #define QMD_IS_TRASHED(x)       ((x) == (void *)(intptr_t)-1)
 162 #else   /* !QUEUE_MACRO_DEBUG_TRASH */
 163 #define QMD_SAVELINK(name, link)
 164 #define TRASHIT(x)
 165 #define QMD_IS_TRASHED(x)       0
 166 #endif  /* QUEUE_MACRO_DEBUG_TRASH */
 167
 168 #ifdef __cplusplus
 169 /*
 170  * In C++ there can be structure lists and class lists:
 171  */
 172 #define QUEUE_TYPEOF(type) type
 173 #else
 174 #define QUEUE_TYPEOF(type) struct type
 175 #endif
 176
 177 /*
 178  * Singly-linked List declarations.
 179  */
 180 #define SLIST_HEAD(name, type)                                          \
 181 struct name {                                                           \
 182         struct type *slh_first; /* first element */                     \
 183 }
 184
 185 #define SLIST_CLASS_HEAD(name, type)                                    \
 186 struct name {                                                           \
 187         class type *slh_first;  /* first element */                     \
 188 }
 189
 190 #define SLIST_HEAD_INITIALIZER(head)                                    \
 191         { NULL }
 192
 193 #define SLIST_ENTRY(type)                                               \
 194 struct {                                                                \
 195         struct type *sle_next;  /* next element */                      \
 196 }
 197
 198 #define SLIST_CLASS_ENTRY(type)                                         \
 199 struct {                                                                \
 200         class type *sle_next;           /* next element */              \
 201 }
 202
 203 /*
 204  * Singly-linked List functions.
 205  */
 206 #if (defined(_KERNEL) && defined(INVARIANTS))
 207 #define QMD_SLIST_CHECK_PREVPTR(prevp, elm) do {                        \
 208         if (*(prevp) != (elm))                                          \
 209                 panic("Bad prevptr *(%p) == %p != %p",                  \
 210                     (prevp), *(prevp), (elm));                          \
 211 } while (0)
 212 #else
 213 #define QMD_SLIST_CHECK_PREVPTR(prevp, elm)
 214 #endif
 215
 216 #define SLIST_CONCAT(head1, head2, type, field) do {                    \
 217         QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head1);                \
 218         if (curelm == NULL) {                                           \
 219                 if ((SLIST_FIRST(head1) = SLIST_FIRST(head2)) != NULL)  \
 220                         SLIST_INIT(head2);                              \
 221         } else if (SLIST_FIRST(head2) != NULL) {                        \
 222                 while (SLIST_NEXT(curelm, field) != NULL)               \
 223                         curelm = SLIST_NEXT(curelm, field);             \
 224                 SLIST_NEXT(curelm, field) = SLIST_FIRST(head2);         \
 225                 SLIST_INIT(head2);                                      \
 226         }                                                               \
 227 } while (0)
 228
 229 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
 230
 231 #define SLIST_FIRST(head)       ((head)->slh_first)
 232
 233 #define SLIST_FOREACH(var, head, field)                                 \
 234         for ((var) = SLIST_FIRST((head));                               \
 235             (var);                                                      \
 236             (var) = SLIST_NEXT((var), field))
 237
 238 #define SLIST_FOREACH_FROM(var, head, field)                            \
 239         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 240             (var);                                                      \
 241             (var) = SLIST_NEXT((var), field))
 242
 243 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
 244         for ((var) = SLIST_FIRST((head));                               \
 245             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 246             (var) = (tvar))
 247
 248 #define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 249         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
 250             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
 251             (var) = (tvar))
 252
 253 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
 254         for ((varp) = &SLIST_FIRST((head));                             \
 255             ((var) = *(varp)) != NULL;                                  \
 256             (varp) = &SLIST_NEXT((var), field))
 257
 258 #define SLIST_INIT(head) do {                                           \
 259         SLIST_FIRST((head)) = NULL;                                     \
 260 } while (0)
 261
 262 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
 263         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
 264         SLIST_NEXT((slistelm), field) = (elm);                          \
 265 } while (0)
 266
 267 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
 268         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
 269         SLIST_FIRST((head)) = (elm);                                    \
 270 } while (0)
 271
 272 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
 273
 274 #define SLIST_REMOVE(head, elm, type, field) do {                       \
 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 } while (0)
 285
 286 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
 287         QMD_SAVELINK(oldnext, SLIST_NEXT(elm, field)->field.sle_next);  \
 288         SLIST_NEXT(elm, field) =                                        \
 289             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
 290         TRASHIT(*oldnext);                                              \
 291 } while (0)
 292
 293 #define SLIST_REMOVE_HEAD(head, field) do {                             \
 294         QMD_SAVELINK(oldnext, SLIST_FIRST(head)->field.sle_next);       \
 295         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
 296         TRASHIT(*oldnext);                                              \
 297 } while (0)
 298
 299 #define SLIST_REMOVE_PREVPTR(prevp, elm, field) do {                    \
 300         QMD_SLIST_CHECK_PREVPTR(prevp, elm);                            \
 301         *(prevp) = SLIST_NEXT(elm, field);                              \
 302         TRASHIT((elm)->field.sle_next);                                 \
 303 } while (0)
 304
 305 #define SLIST_SWAP(head1, head2, type) do {                             \
 306         QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
 307         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
 308         SLIST_FIRST(head2) = swap_first;                                \
 309 } while (0)
 310
 311 #define SLIST_END(head)         NULL
 312
 313 /*
 314  * Singly-linked Tail queue declarations.
 315  */
 316 #define STAILQ_HEAD(name, type)                                         \
 317 struct name {                                                           \
 318         struct type *stqh_first;/* first element */                     \
 319         struct type **stqh_last;/* addr of last next element */         \
 320 }
 321
 322 #define STAILQ_CLASS_HEAD(name, type)                                   \
 323 struct name {                                                           \
 324         class type *stqh_first; /* first element */                     \
 325         class type **stqh_last; /* addr of last next element */         \
 326 }
 327
 328 #define STAILQ_HEAD_INITIALIZER(head)                                   \
 329         { NULL, &(head).stqh_first }
 330
 331 #define STAILQ_ENTRY(type)                                              \
 332 struct {                                                                \
 333         struct type *stqe_next; /* next element */                      \
 334 }
 335
 336 #define STAILQ_CLASS_ENTRY(type)                                        \
 337 struct {                                                                \
 338         class type *stqe_next;  /* next element */                      \
 339 }
 340
 341 /*
 342  * Singly-linked Tail queue functions.
 343  */
 344 #define STAILQ_CONCAT(head1, head2) do {                                \
 345         if (!STAILQ_EMPTY((head2))) {                                   \
 346                 *(head1)->stqh_last = (head2)->stqh_first;              \
 347                 (head1)->stqh_last = (head2)->stqh_last;                \
 348                 STAILQ_INIT((head2));                                   \
 349         }                                                               \
 350 } while (0)
 351
 352 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
 353
 354 #define STAILQ_FIRST(head)      ((head)->stqh_first)
 355
 356 #define STAILQ_FOREACH(var, head, field)                                \
 357         for((var) = STAILQ_FIRST((head));                               \
 358            (var);                                                       \
 359            (var) = STAILQ_NEXT((var), field))
 360
 361 #define STAILQ_FOREACH_FROM(var, head, field)                           \
 362         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 363            (var);                                                       \
 364            (var) = STAILQ_NEXT((var), field))
 365
 366 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
 367         for ((var) = STAILQ_FIRST((head));                              \
 368             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 369             (var) = (tvar))
 370
 371 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
 372         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
 373             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
 374             (var) = (tvar))
 375
 376 #define STAILQ_INIT(head) do {                                          \
 377         STAILQ_FIRST((head)) = NULL;                                    \
 378         (head)->stqh_last = &STAILQ_FIRST((head));                      \
 379 } while (0)
 380
 381 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
 382         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
 383                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 384         STAILQ_NEXT((tqelm), field) = (elm);                            \
 385 } while (0)
 386
 387 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
 388         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
 389                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 390         STAILQ_FIRST((head)) = (elm);                                   \
 391 } while (0)
 392
 393 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
 394         STAILQ_NEXT((elm), field) = NULL;                               \
 395         *(head)->stqh_last = (elm);                                     \
 396         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
 397 } while (0)
 398
 399 #define STAILQ_LAST(head, type, field)                          \
 400         (STAILQ_EMPTY((head)) ? NULL :                          \
 401             __containerof((head)->stqh_last,                    \
 402             QUEUE_TYPEOF(type), field.stqe_next))
 403
 404 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
 405
 406 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
 407         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
 408         if (STAILQ_FIRST((head)) == (elm)) {                            \
 409                 STAILQ_REMOVE_HEAD((head), field);                      \
 410         }                                                               \
 411         else {                                                          \
 412                 QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
 413                 while (STAILQ_NEXT(curelm, field) != (elm))             \
 414                         curelm = STAILQ_NEXT(curelm, field);            \
 415                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
 416         }                                                               \
 417         TRASHIT(*oldnext);                                              \
 418 } while (0)
 419
 420 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
 421         if ((STAILQ_NEXT(elm, field) =                                  \
 422              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
 423                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
 424 } while (0)
 425
 426 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
 427         if ((STAILQ_FIRST((head)) =                                     \
 428              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
 429                 (head)->stqh_last = &STAILQ_FIRST((head));              \
 430 } while (0)
 431
 432 #define STAILQ_SWAP(head1, head2, type) do {                            \
 433         QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
 434         QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
 435         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
 436         (head1)->stqh_last = (head2)->stqh_last;                        \
 437         STAILQ_FIRST(head2) = swap_first;                               \
 438         (head2)->stqh_last = swap_last;                                 \
 439         if (STAILQ_EMPTY(head1))                                        \
 440                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
 441         if (STAILQ_EMPTY(head2))                                        \
 442                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
 443 } while (0)
 444
 445 #define STAILQ_END(head)        NULL
 446
 447
 448 /*
 449  * List declarations.
 450  */
 451 #define LIST_HEAD(name, type)                                           \
 452 struct name {                                                           \
 453         struct type *lh_first;  /* first element */                     \
 454 }
 455
 456 #define LIST_CLASS_HEAD(name, type)                                     \
 457 struct name {                                                           \
 458         class type *lh_first;   /* first element */                     \
 459 }
 460
 461 #define LIST_HEAD_INITIALIZER(head)                                     \
 462         { NULL }
 463
 464 #define LIST_ENTRY(type)                                                \
 465 struct {                                                                \
 466         struct type *le_next;   /* next element */                      \
 467         struct type **le_prev;  /* address of previous next element */  \
 468 }
 469
 470 #define LIST_CLASS_ENTRY(type)                                          \
 471 struct {                                                                \
 472         class type *le_next;    /* next element */                      \
 473         class type **le_prev;   /* address of previous next element */  \
 474 }
 475
 476 /*
 477  * List functions.
 478  */
 479
 480 #if (defined(_KERNEL) && defined(INVARIANTS))
 481 /*
 482  * QMD_LIST_CHECK_HEAD(LIST_HEAD *head, LIST_ENTRY NAME)
 483  *
 484  * If the list is non-empty, validates that the first element of the list
 485  * points back at 'head.'
 486  */
 487 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
 488         if (LIST_FIRST((head)) != NULL &&                               \
 489             LIST_FIRST((head))->field.le_prev !=                        \
 490              &LIST_FIRST((head)))                                       \
 491                 panic("Bad list head %p first->prev != head", (head));  \
 492 } while (0)
 493
 494 /*
 495  * QMD_LIST_CHECK_NEXT(TYPE *elm, LIST_ENTRY NAME)
 496  *
 497  * If an element follows 'elm' in the list, validates that the next element
 498  * points back at 'elm.'
 499  */
 500 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
 501         if (LIST_NEXT((elm), field) != NULL &&                          \
 502             LIST_NEXT((elm), field)->field.le_prev !=                   \
 503              &((elm)->field.le_next))                                   \
 504                 panic("Bad link elm %p next->prev != elm", (elm));      \
 505 } while (0)
 506
 507 /*
 508  * QMD_LIST_CHECK_PREV(TYPE *elm, LIST_ENTRY NAME)
 509  *
 510  * Validates that the previous element (or head of the list) points to 'elm.'
 511  */
 512 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
 513         if (*(elm)->field.le_prev != (elm))                             \
 514                 panic("Bad link elm %p prev->next != elm", (elm));      \
 515 } while (0)
 516 #else
 517 #define QMD_LIST_CHECK_HEAD(head, field)
 518 #define QMD_LIST_CHECK_NEXT(elm, field)
 519 #define QMD_LIST_CHECK_PREV(elm, field)
 520 #endif /* (_KERNEL && INVARIANTS) */
 521
 522 #define LIST_CONCAT(head1, head2, type, field) do {                           \
 523         QUEUE_TYPEOF(type) *curelm = LIST_FIRST(head1);                       \
 524         if (curelm == NULL) {                                                 \
 525                 if ((LIST_FIRST(head1) = LIST_FIRST(head2)) != NULL) {        \
 526                         LIST_FIRST(head2)->field.le_prev =                    \
 527                             &LIST_FIRST((head1));                             \
 528                         LIST_INIT(head2);                                     \
 529                 }                                                             \
 530         } else if (LIST_FIRST(head2) != NULL) {                               \
 531                 while (LIST_NEXT(curelm, field) != NULL)                      \
 532                         curelm = LIST_NEXT(curelm, field);                    \
 533                 LIST_NEXT(curelm, field) = LIST_FIRST(head2);                 \
 534                 LIST_FIRST(head2)->field.le_prev = &LIST_NEXT(curelm, field); \
 535                 LIST_INIT(head2);                                             \
 536         }                                                                     \
 537 } while (0)
 538
 539 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
 540
 541 #define LIST_FIRST(head)        ((head)->lh_first)
 542
 543 #define LIST_FOREACH(var, head, field)                                  \
 544         for ((var) = LIST_FIRST((head));                                \
 545             (var);                                                      \
 546             (var) = LIST_NEXT((var), field))
 547
 548 #define LIST_FOREACH_FROM(var, head, field)                             \
 549         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 550             (var);                                                      \
 551             (var) = LIST_NEXT((var), field))
 552
 553 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
 554         for ((var) = LIST_FIRST((head));                                \
 555             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 556             (var) = (tvar))
 557
 558 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
 559         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
 560             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
 561             (var) = (tvar))
 562
 563 #define LIST_INIT(head) do {                                            \
 564         LIST_FIRST((head)) = NULL;                                      \
 565 } while (0)
 566
 567 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
 568         QMD_LIST_CHECK_NEXT(listelm, field);                            \
 569         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
 570                 LIST_NEXT((listelm), field)->field.le_prev =            \
 571                     &LIST_NEXT((elm), field);                           \
 572         LIST_NEXT((listelm), field) = (elm);                            \
 573         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
 574 } while (0)
 575
 576 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
 577         QMD_LIST_CHECK_PREV(listelm, field);                            \
 578         (elm)->field.le_prev = (listelm)->field.le_prev;                \
 579         LIST_NEXT((elm), field) = (listelm);                            \
 580         *(listelm)->field.le_prev = (elm);                              \
 581         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
 582 } while (0)
 583
 584 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
 585         QMD_LIST_CHECK_HEAD((head), field);                             \
 586         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
 587                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
 588         LIST_FIRST((head)) = (elm);                                     \
 589         (elm)->field.le_prev = &LIST_FIRST((head));                     \
 590 } while (0)
 591
 592 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
 593
 594 #define LIST_PREV(elm, head, type, field)                       \
 595         ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
 596             __containerof((elm)->field.le_prev,                 \
 597             QUEUE_TYPEOF(type), field.le_next))
 598
 599 #define LIST_REMOVE(elm, field) do {                                    \
 600         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
 601         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
 602         QMD_LIST_CHECK_NEXT(elm, field);                                \
 603         QMD_LIST_CHECK_PREV(elm, field);                                \
 604         if (LIST_NEXT((elm), field) != NULL)                            \
 605                 LIST_NEXT((elm), field)->field.le_prev =                \
 606                     (elm)->field.le_prev;                               \
 607         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
 608         TRASHIT(*oldnext);                                              \
 609         TRASHIT(*oldprev);                                              \
 610 } while (0)
 611
 612 #define LIST_SWAP(head1, head2, type, field) do {                       \
 613         QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
 614         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
 615         LIST_FIRST((head2)) = swap_tmp;                                 \
 616         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
 617                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
 618         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
 619                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
 620 } while (0)
 621
 622 #define LIST_END(head)  NULL
 623
 624 /*
 625  * Tail queue declarations.
 626  */
 627 #define TAILQ_HEAD(name, type)                                          \
 628 struct name {                                                           \
 629         struct type *tqh_first; /* first element */                     \
 630         struct type **tqh_last; /* addr of last next element */         \
 631         TRACEBUF                                                        \
 632 }
 633
 634 #define TAILQ_CLASS_HEAD(name, type)                                    \
 635 struct name {                                                           \
 636         class type *tqh_first;  /* first element */                     \
 637         class type **tqh_last;  /* addr of last next element */         \
 638         TRACEBUF                                                        \
 639 }
 640
 641 #define TAILQ_HEAD_INITIALIZER(head)                                    \
 642         { NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }
 643
 644 #define TAILQ_ENTRY(type)                                               \
 645 struct {                                                                \
 646         struct type *tqe_next;  /* next element */                      \
 647         struct type **tqe_prev; /* address of previous next element */  \
 648         TRACEBUF                                                        \
 649 }
 650
 651 #define TAILQ_CLASS_ENTRY(type)                                         \
 652 struct {                                                                \
 653         class type *tqe_next;   /* next element */                      \
 654         class type **tqe_prev;  /* address of previous next element */  \
 655         TRACEBUF                                                        \
 656 }
 657
 658 /*
 659  * Tail queue functions.
 660  */
 661 #if (defined(_KERNEL) && defined(INVARIANTS))
 662 /*
 663  * QMD_TAILQ_CHECK_HEAD(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
 664  *
 665  * If the tailq is non-empty, validates that the first element of the tailq
 666  * points back at 'head.'
 667  */
 668 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
 669         if (!TAILQ_EMPTY(head) &&                                       \
 670             TAILQ_FIRST((head))->field.tqe_prev !=                      \
 671              &TAILQ_FIRST((head)))                                      \
 672                 panic("Bad tailq head %p first->prev != head", (head)); \
 673 } while (0)
 674
 675 /*
 676  * QMD_TAILQ_CHECK_TAIL(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
 677  *
 678  * Validates that the tail of the tailq is a pointer to pointer to NULL.
 679  */
 680 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
 681         if (*(head)->tqh_last != NULL)                                  \
 682                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
 683 } while (0)
 684
 685 /*
 686  * QMD_TAILQ_CHECK_NEXT(TYPE *elm, TAILQ_ENTRY NAME)
 687  *
 688  * If an element follows 'elm' in the tailq, validates that the next element
 689  * points back at 'elm.'
 690  */
 691 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
 692         if (TAILQ_NEXT((elm), field) != NULL &&                         \
 693             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
 694              &((elm)->field.tqe_next))                                  \
 695                 panic("Bad link elm %p next->prev != elm", (elm));      \
 696 } while (0)
 697
 698 /*
 699  * QMD_TAILQ_CHECK_PREV(TYPE *elm, TAILQ_ENTRY NAME)
 700  *
 701  * Validates that the previous element (or head of the tailq) points to 'elm.'
 702  */
 703 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
 704         if (*(elm)->field.tqe_prev != (elm))                            \
 705                 panic("Bad link elm %p prev->next != elm", (elm));      \
 706 } while (0)
 707 #else
 708 #define QMD_TAILQ_CHECK_HEAD(head, field)
 709 #define QMD_TAILQ_CHECK_TAIL(head, headname)
 710 #define QMD_TAILQ_CHECK_NEXT(elm, field)
 711 #define QMD_TAILQ_CHECK_PREV(elm, field)
 712 #endif /* (_KERNEL && INVARIANTS) */
 713
 714 #define TAILQ_CONCAT(head1, head2, field) do {                          \
 715         if (!TAILQ_EMPTY(head2)) {                                      \
 716                 *(head1)->tqh_last = (head2)->tqh_first;                \
 717                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
 718                 (head1)->tqh_last = (head2)->tqh_last;                  \
 719                 TAILQ_INIT((head2));                                    \
 720                 QMD_TRACE_HEAD(head1);                                  \
 721                 QMD_TRACE_HEAD(head2);                                  \
 722         }                                                               \
 723 } while (0)
 724
 725 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
 726
 727 #define TAILQ_FIRST(head)       ((head)->tqh_first)
 728
 729 #define TAILQ_FOREACH(var, head, field)                                 \
 730         for ((var) = TAILQ_FIRST((head));                               \
 731             (var);                                                      \
 732             (var) = TAILQ_NEXT((var), field))
 733
 734 #define TAILQ_FOREACH_FROM(var, head, field)                            \
 735         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 736             (var);                                                      \
 737             (var) = TAILQ_NEXT((var), field))
 738
 739 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
 740         for ((var) = TAILQ_FIRST((head));                               \
 741             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 742             (var) = (tvar))
 743
 744 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
 745         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
 746             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
 747             (var) = (tvar))
 748
 749 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
 750         for ((var) = TAILQ_LAST((head), headname);                      \
 751             (var);                                                      \
 752             (var) = TAILQ_PREV((var), headname, field))
 753
 754 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)          \
 755         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 756             (var);                                                      \
 757             (var) = TAILQ_PREV((var), headname, field))
 758
 759 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
 760         for ((var) = TAILQ_LAST((head), headname);                      \
 761             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 762             (var) = (tvar))
 763
 764 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
 765         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
 766             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
 767             (var) = (tvar))
 768
 769 #define TAILQ_INIT(head) do {                                           \
 770         TAILQ_FIRST((head)) = NULL;                                     \
 771         (head)->tqh_last = &TAILQ_FIRST((head));                        \
 772         QMD_TRACE_HEAD(head);                                           \
 773 } while (0)
 774
 775 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
 776         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
 777         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
 778                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 779                     &TAILQ_NEXT((elm), field);                          \
 780         else {                                                          \
 781                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 782                 QMD_TRACE_HEAD(head);                                   \
 783         }                                                               \
 784         TAILQ_NEXT((listelm), field) = (elm);                           \
 785         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
 786         QMD_TRACE_ELEM(&(elm)->field);                                  \
 787         QMD_TRACE_ELEM(&(listelm)->field);                              \
 788 } while (0)
 789
 790 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
 791         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
 792         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
 793         TAILQ_NEXT((elm), field) = (listelm);                           \
 794         *(listelm)->field.tqe_prev = (elm);                             \
 795         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
 796         QMD_TRACE_ELEM(&(elm)->field);                                  \
 797         QMD_TRACE_ELEM(&(listelm)->field);                              \
 798 } while (0)
 799
 800 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
 801         QMD_TAILQ_CHECK_HEAD(head, field);                              \
 802         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
 803                 TAILQ_FIRST((head))->field.tqe_prev =                   \
 804                     &TAILQ_NEXT((elm), field);                          \
 805         else                                                            \
 806                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
 807         TAILQ_FIRST((head)) = (elm);                                    \
 808         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
 809         QMD_TRACE_HEAD(head);                                           \
 810         QMD_TRACE_ELEM(&(elm)->field);                                  \
 811 } while (0)
 812
 813 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
 814         QMD_TAILQ_CHECK_TAIL(head, field);                              \
 815         TAILQ_NEXT((elm), field) = NULL;                                \
 816         (elm)->field.tqe_prev = (head)->tqh_last;                       \
 817         *(head)->tqh_last = (elm);                                      \
 818         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
 819         QMD_TRACE_HEAD(head);                                           \
 820         QMD_TRACE_ELEM(&(elm)->field);                                  \
 821 } while (0)
 822
 823 #define TAILQ_LAST(head, headname)                                      \
 824         (*(((struct headname *)((head)->tqh_last))->tqh_last))
 825
 826 /*
 827  * The FAST function is fast in that it causes no data access other
 828  * then the access to the head. The standard LAST function above
 829  * will cause a data access of both the element you want and
 830  * the previous element. FAST is very useful for instances when
 831  * you may want to prefetch the last data element.
 832  */
 833 #define TAILQ_LAST_FAST(head, type, field)                      \
 834     (TAILQ_EMPTY(head) ? NULL : __containerof((head)->tqh_last, QUEUE_TYPEOF(type), field.tqe_next))
 835
 836 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
 837
 838 #define TAILQ_PREV(elm, headname, field)                                \
 839         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 840
 841 #define TAILQ_PREV_FAST(elm, head, type, field)                         \
 842     ((elm)->field.tqe_prev == &(head)->tqh_first ? NULL :               \
 843      __containerof((elm)->field.tqe_prev, QUEUE_TYPEOF(type), field.tqe_next))
 844
 845 #define TAILQ_REMOVE(head, elm, field) do {                             \
 846         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
 847         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
 848         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
 849         QMD_TAILQ_CHECK_PREV(elm, field);                               \
 850         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
 851                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
 852                     (elm)->field.tqe_prev;                              \
 853         else {                                                          \
 854                 (head)->tqh_last = (elm)->field.tqe_prev;               \
 855                 QMD_TRACE_HEAD(head);                                   \
 856         }                                                               \
 857         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
 858         TRASHIT(*oldnext);                                              \
 859         TRASHIT(*oldprev);                                              \
 860         QMD_TRACE_ELEM(&(elm)->field);                                  \
 861 } while (0)
 862
 863 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
 864         QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
 865         QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
 866         (head1)->tqh_first = (head2)->tqh_first;                        \
 867         (head1)->tqh_last = (head2)->tqh_last;                          \
 868         (head2)->tqh_first = swap_first;                                \
 869         (head2)->tqh_last = swap_last;                                  \
 870         if ((swap_first = (head1)->tqh_first) != NULL)                  \
 871                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
 872         else                                                            \
 873                 (head1)->tqh_last = &(head1)->tqh_first;                \
 874         if ((swap_first = (head2)->tqh_first) != NULL)                  \
 875                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
 876         else                                                            \
 877                 (head2)->tqh_last = &(head2)->tqh_first;                \
 878 } while (0)
 879
 880 #define TAILQ_END(head)         NULL
 881
 882 #endif /* !_SYS_QUEUE_H_ */