The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/sys/queue.h

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    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         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
  276         if (SLIST_FIRST((head)) == (elm)) {                             \
  277                 SLIST_REMOVE_HEAD((head), field);                       \
  278         }                                                               \
  279         else {                                                          \
  280                 QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head);         \
  281                 while (SLIST_NEXT(curelm, field) != (elm))              \
  282                         curelm = SLIST_NEXT(curelm, field);             \
  283                 SLIST_REMOVE_AFTER(curelm, field);                      \
  284         }                                                               \
  285         TRASHIT(*oldnext);                                              \
  286 } while (0)
  287 
  288 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
  289         SLIST_NEXT(elm, field) =                                        \
  290             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
  291 } while (0)
  292 
  293 #define SLIST_REMOVE_HEAD(head, field) do {                             \
  294         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
  295 } while (0)
  296 
  297 #define SLIST_REMOVE_PREVPTR(prevp, elm, field) do {                    \
  298         QMD_SLIST_CHECK_PREVPTR(prevp, elm);                            \
  299         *(prevp) = SLIST_NEXT(elm, field);                              \
  300         TRASHIT((elm)->field.sle_next);                                 \
  301 } while (0)
  302 
  303 #define SLIST_SWAP(head1, head2, type) do {                             \
  304         QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
  305         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
  306         SLIST_FIRST(head2) = swap_first;                                \
  307 } while (0)
  308 
  309 #define SLIST_END(head)         NULL
  310 
  311 /*
  312  * Singly-linked Tail queue declarations.
  313  */
  314 #define STAILQ_HEAD(name, type)                                         \
  315 struct name {                                                           \
  316         struct type *stqh_first;/* first element */                     \
  317         struct type **stqh_last;/* addr of last next element */         \
  318 }
  319 
  320 #define STAILQ_CLASS_HEAD(name, type)                                   \
  321 struct name {                                                           \
  322         class type *stqh_first; /* first element */                     \
  323         class type **stqh_last; /* addr of last next element */         \
  324 }
  325 
  326 #define STAILQ_HEAD_INITIALIZER(head)                                   \
  327         { NULL, &(head).stqh_first }
  328 
  329 #define STAILQ_ENTRY(type)                                              \
  330 struct {                                                                \
  331         struct type *stqe_next; /* next element */                      \
  332 }
  333 
  334 #define STAILQ_CLASS_ENTRY(type)                                        \
  335 struct {                                                                \
  336         class type *stqe_next;  /* next element */                      \
  337 }
  338 
  339 /*
  340  * Singly-linked Tail queue functions.
  341  */
  342 #define STAILQ_CONCAT(head1, head2) do {                                \
  343         if (!STAILQ_EMPTY((head2))) {                                   \
  344                 *(head1)->stqh_last = (head2)->stqh_first;              \
  345                 (head1)->stqh_last = (head2)->stqh_last;                \
  346                 STAILQ_INIT((head2));                                   \
  347         }                                                               \
  348 } while (0)
  349 
  350 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
  351 
  352 #define STAILQ_FIRST(head)      ((head)->stqh_first)
  353 
  354 #define STAILQ_FOREACH(var, head, field)                                \
  355         for((var) = STAILQ_FIRST((head));                               \
  356            (var);                                                       \
  357            (var) = STAILQ_NEXT((var), field))
  358 
  359 #define STAILQ_FOREACH_FROM(var, head, field)                           \
  360         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
  361            (var);                                                       \
  362            (var) = STAILQ_NEXT((var), field))
  363 
  364 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
  365         for ((var) = STAILQ_FIRST((head));                              \
  366             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
  367             (var) = (tvar))
  368 
  369 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
  370         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
  371             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
  372             (var) = (tvar))
  373 
  374 #define STAILQ_INIT(head) do {                                          \
  375         STAILQ_FIRST((head)) = NULL;                                    \
  376         (head)->stqh_last = &STAILQ_FIRST((head));                      \
  377 } while (0)
  378 
  379 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
  380         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
  381                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
  382         STAILQ_NEXT((tqelm), field) = (elm);                            \
  383 } while (0)
  384 
  385 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
  386         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
  387                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
  388         STAILQ_FIRST((head)) = (elm);                                   \
  389 } while (0)
  390 
  391 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
  392         STAILQ_NEXT((elm), field) = NULL;                               \
  393         *(head)->stqh_last = (elm);                                     \
  394         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
  395 } while (0)
  396 
  397 #define STAILQ_LAST(head, type, field)                          \
  398         (STAILQ_EMPTY((head)) ? NULL :                          \
  399             __containerof((head)->stqh_last,                    \
  400             QUEUE_TYPEOF(type), field.stqe_next))
  401 
  402 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
  403 
  404 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
  405         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
  406         if (STAILQ_FIRST((head)) == (elm)) {                            \
  407                 STAILQ_REMOVE_HEAD((head), field);                      \
  408         }                                                               \
  409         else {                                                          \
  410                 QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
  411                 while (STAILQ_NEXT(curelm, field) != (elm))             \
  412                         curelm = STAILQ_NEXT(curelm, field);            \
  413                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
  414         }                                                               \
  415         TRASHIT(*oldnext);                                              \
  416 } while (0)
  417 
  418 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
  419         if ((STAILQ_NEXT(elm, field) =                                  \
  420              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
  421                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
  422 } while (0)
  423 
  424 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
  425         if ((STAILQ_FIRST((head)) =                                     \
  426              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
  427                 (head)->stqh_last = &STAILQ_FIRST((head));              \
  428 } while (0)
  429 
  430 #define STAILQ_SWAP(head1, head2, type) do {                            \
  431         QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
  432         QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
  433         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
  434         (head1)->stqh_last = (head2)->stqh_last;                        \
  435         STAILQ_FIRST(head2) = swap_first;                               \
  436         (head2)->stqh_last = swap_last;                                 \
  437         if (STAILQ_EMPTY(head1))                                        \
  438                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
  439         if (STAILQ_EMPTY(head2))                                        \
  440                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
  441 } while (0)
  442 
  443 #define STAILQ_END(head)        NULL
  444 
  445 
  446 /*
  447  * List declarations.
  448  */
  449 #define LIST_HEAD(name, type)                                           \
  450 struct name {                                                           \
  451         struct type *lh_first;  /* first element */                     \
  452 }
  453 
  454 #define LIST_CLASS_HEAD(name, type)                                     \
  455 struct name {                                                           \
  456         class type *lh_first;   /* first element */                     \
  457 }
  458 
  459 #define LIST_HEAD_INITIALIZER(head)                                     \
  460         { NULL }
  461 
  462 #define LIST_ENTRY(type)                                                \
  463 struct {                                                                \
  464         struct type *le_next;   /* next element */                      \
  465         struct type **le_prev;  /* address of previous next element */  \
  466 }
  467 
  468 #define LIST_CLASS_ENTRY(type)                                          \
  469 struct {                                                                \
  470         class type *le_next;    /* next element */                      \
  471         class type **le_prev;   /* address of previous next element */  \
  472 }
  473 
  474 /*
  475  * List functions.
  476  */
  477 
  478 #if (defined(_KERNEL) && defined(INVARIANTS))
  479 /*
  480  * QMD_LIST_CHECK_HEAD(LIST_HEAD *head, LIST_ENTRY NAME)
  481  *
  482  * If the list is non-empty, validates that the first element of the list
  483  * points back at 'head.'
  484  */
  485 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
  486         if (LIST_FIRST((head)) != NULL &&                               \
  487             LIST_FIRST((head))->field.le_prev !=                        \
  488              &LIST_FIRST((head)))                                       \
  489                 panic("Bad list head %p first->prev != head", (head));  \
  490 } while (0)
  491 
  492 /*
  493  * QMD_LIST_CHECK_NEXT(TYPE *elm, LIST_ENTRY NAME)
  494  *
  495  * If an element follows 'elm' in the list, validates that the next element
  496  * points back at 'elm.'
  497  */
  498 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
  499         if (LIST_NEXT((elm), field) != NULL &&                          \
  500             LIST_NEXT((elm), field)->field.le_prev !=                   \
  501              &((elm)->field.le_next))                                   \
  502                 panic("Bad link elm %p next->prev != elm", (elm));      \
  503 } while (0)
  504 
  505 /*
  506  * QMD_LIST_CHECK_PREV(TYPE *elm, LIST_ENTRY NAME)
  507  *
  508  * Validates that the previous element (or head of the list) points to 'elm.'
  509  */
  510 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
  511         if (*(elm)->field.le_prev != (elm))                             \
  512                 panic("Bad link elm %p prev->next != elm", (elm));      \
  513 } while (0)
  514 #else
  515 #define QMD_LIST_CHECK_HEAD(head, field)
  516 #define QMD_LIST_CHECK_NEXT(elm, field)
  517 #define QMD_LIST_CHECK_PREV(elm, field)
  518 #endif /* (_KERNEL && INVARIANTS) */
  519 
  520 #define LIST_CONCAT(head1, head2, type, field) do {                           \
  521         QUEUE_TYPEOF(type) *curelm = LIST_FIRST(head1);                       \
  522         if (curelm == NULL) {                                                 \
  523                 if ((LIST_FIRST(head1) = LIST_FIRST(head2)) != NULL) {        \
  524                         LIST_FIRST(head2)->field.le_prev =                    \
  525                             &LIST_FIRST((head1));                             \
  526                         LIST_INIT(head2);                                     \
  527                 }                                                             \
  528         } else if (LIST_FIRST(head2) != NULL) {                               \
  529                 while (LIST_NEXT(curelm, field) != NULL)                      \
  530                         curelm = LIST_NEXT(curelm, field);                    \
  531                 LIST_NEXT(curelm, field) = LIST_FIRST(head2);                 \
  532                 LIST_FIRST(head2)->field.le_prev = &LIST_NEXT(curelm, field); \
  533                 LIST_INIT(head2);                                             \
  534         }                                                                     \
  535 } while (0)
  536 
  537 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
  538 
  539 #define LIST_FIRST(head)        ((head)->lh_first)
  540 
  541 #define LIST_FOREACH(var, head, field)                                  \
  542         for ((var) = LIST_FIRST((head));                                \
  543             (var);                                                      \
  544             (var) = LIST_NEXT((var), field))
  545 
  546 #define LIST_FOREACH_FROM(var, head, field)                             \
  547         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
  548             (var);                                                      \
  549             (var) = LIST_NEXT((var), field))
  550 
  551 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
  552         for ((var) = LIST_FIRST((head));                                \
  553             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
  554             (var) = (tvar))
  555 
  556 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
  557         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
  558             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
  559             (var) = (tvar))
  560 
  561 #define LIST_INIT(head) do {                                            \
  562         LIST_FIRST((head)) = NULL;                                      \
  563 } while (0)
  564 
  565 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
  566         QMD_LIST_CHECK_NEXT(listelm, field);                            \
  567         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
  568                 LIST_NEXT((listelm), field)->field.le_prev =            \
  569                     &LIST_NEXT((elm), field);                           \
  570         LIST_NEXT((listelm), field) = (elm);                            \
  571         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
  572 } while (0)
  573 
  574 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
  575         QMD_LIST_CHECK_PREV(listelm, field);                            \
  576         (elm)->field.le_prev = (listelm)->field.le_prev;                \
  577         LIST_NEXT((elm), field) = (listelm);                            \
  578         *(listelm)->field.le_prev = (elm);                              \
  579         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
  580 } while (0)
  581 
  582 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
  583         QMD_LIST_CHECK_HEAD((head), field);                             \
  584         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
  585                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
  586         LIST_FIRST((head)) = (elm);                                     \
  587         (elm)->field.le_prev = &LIST_FIRST((head));                     \
  588 } while (0)
  589 
  590 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
  591 
  592 #define LIST_PREV(elm, head, type, field)                       \
  593         ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
  594             __containerof((elm)->field.le_prev,                 \
  595             QUEUE_TYPEOF(type), field.le_next))
  596 
  597 #define LIST_REMOVE(elm, field) do {                                    \
  598         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
  599         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
  600         QMD_LIST_CHECK_NEXT(elm, field);                                \
  601         QMD_LIST_CHECK_PREV(elm, field);                                \
  602         if (LIST_NEXT((elm), field) != NULL)                            \
  603                 LIST_NEXT((elm), field)->field.le_prev =                \
  604                     (elm)->field.le_prev;                               \
  605         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
  606         TRASHIT(*oldnext);                                              \
  607         TRASHIT(*oldprev);                                              \
  608 } while (0)
  609 
  610 #define LIST_SWAP(head1, head2, type, field) do {                       \
  611         QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
  612         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
  613         LIST_FIRST((head2)) = swap_tmp;                                 \
  614         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
  615                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
  616         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
  617                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
  618 } while (0)
  619 
  620 #define LIST_END(head)  NULL
  621 
  622 /*
  623  * Tail queue declarations.
  624  */
  625 #define TAILQ_HEAD(name, type)                                          \
  626 struct name {                                                           \
  627         struct type *tqh_first; /* first element */                     \
  628         struct type **tqh_last; /* addr of last next element */         \
  629         TRACEBUF                                                        \
  630 }
  631 
  632 #define TAILQ_CLASS_HEAD(name, type)                                    \
  633 struct name {                                                           \
  634         class type *tqh_first;  /* first element */                     \
  635         class type **tqh_last;  /* addr of last next element */         \
  636         TRACEBUF                                                        \
  637 }
  638 
  639 #define TAILQ_HEAD_INITIALIZER(head)                                    \
  640         { NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }
  641 
  642 #define TAILQ_ENTRY(type)                                               \
  643 struct {                                                                \
  644         struct type *tqe_next;  /* next element */                      \
  645         struct type **tqe_prev; /* address of previous next element */  \
  646         TRACEBUF                                                        \
  647 }
  648 
  649 #define TAILQ_CLASS_ENTRY(type)                                         \
  650 struct {                                                                \
  651         class type *tqe_next;   /* next element */                      \
  652         class type **tqe_prev;  /* address of previous next element */  \
  653         TRACEBUF                                                        \
  654 }
  655 
  656 /*
  657  * Tail queue functions.
  658  */
  659 #if (defined(_KERNEL) && defined(INVARIANTS))
  660 /*
  661  * QMD_TAILQ_CHECK_HEAD(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
  662  *
  663  * If the tailq is non-empty, validates that the first element of the tailq
  664  * points back at 'head.'
  665  */
  666 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
  667         if (!TAILQ_EMPTY(head) &&                                       \
  668             TAILQ_FIRST((head))->field.tqe_prev !=                      \
  669              &TAILQ_FIRST((head)))                                      \
  670                 panic("Bad tailq head %p first->prev != head", (head)); \
  671 } while (0)
  672 
  673 /*
  674  * QMD_TAILQ_CHECK_TAIL(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
  675  *
  676  * Validates that the tail of the tailq is a pointer to pointer to NULL.
  677  */
  678 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
  679         if (*(head)->tqh_last != NULL)                                  \
  680                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
  681 } while (0)
  682 
  683 /*
  684  * QMD_TAILQ_CHECK_NEXT(TYPE *elm, TAILQ_ENTRY NAME)
  685  *
  686  * If an element follows 'elm' in the tailq, validates that the next element
  687  * points back at 'elm.'
  688  */
  689 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
  690         if (TAILQ_NEXT((elm), field) != NULL &&                         \
  691             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
  692              &((elm)->field.tqe_next))                                  \
  693                 panic("Bad link elm %p next->prev != elm", (elm));      \
  694 } while (0)
  695 
  696 /*
  697  * QMD_TAILQ_CHECK_PREV(TYPE *elm, TAILQ_ENTRY NAME)
  698  *
  699  * Validates that the previous element (or head of the tailq) points to 'elm.'
  700  */
  701 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
  702         if (*(elm)->field.tqe_prev != (elm))                            \
  703                 panic("Bad link elm %p prev->next != elm", (elm));      \
  704 } while (0)
  705 #else
  706 #define QMD_TAILQ_CHECK_HEAD(head, field)
  707 #define QMD_TAILQ_CHECK_TAIL(head, headname)
  708 #define QMD_TAILQ_CHECK_NEXT(elm, field)
  709 #define QMD_TAILQ_CHECK_PREV(elm, field)
  710 #endif /* (_KERNEL && INVARIANTS) */
  711 
  712 #define TAILQ_CONCAT(head1, head2, field) do {                          \
  713         if (!TAILQ_EMPTY(head2)) {                                      \
  714                 *(head1)->tqh_last = (head2)->tqh_first;                \
  715                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
  716                 (head1)->tqh_last = (head2)->tqh_last;                  \
  717                 TAILQ_INIT((head2));                                    \
  718                 QMD_TRACE_HEAD(head1);                                  \
  719                 QMD_TRACE_HEAD(head2);                                  \
  720         }                                                               \
  721 } while (0)
  722 
  723 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
  724 
  725 #define TAILQ_FIRST(head)       ((head)->tqh_first)
  726 
  727 #define TAILQ_FOREACH(var, head, field)                                 \
  728         for ((var) = TAILQ_FIRST((head));                               \
  729             (var);                                                      \
  730             (var) = TAILQ_NEXT((var), field))
  731 
  732 #define TAILQ_FOREACH_FROM(var, head, field)                            \
  733         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
  734             (var);                                                      \
  735             (var) = TAILQ_NEXT((var), field))
  736 
  737 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
  738         for ((var) = TAILQ_FIRST((head));                               \
  739             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
  740             (var) = (tvar))
  741 
  742 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
  743         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
  744             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
  745             (var) = (tvar))
  746 
  747 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
  748         for ((var) = TAILQ_LAST((head), headname);                      \
  749             (var);                                                      \
  750             (var) = TAILQ_PREV((var), headname, field))
  751 
  752 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)          \
  753         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
  754             (var);                                                      \
  755             (var) = TAILQ_PREV((var), headname, field))
  756 
  757 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
  758         for ((var) = TAILQ_LAST((head), headname);                      \
  759             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
  760             (var) = (tvar))
  761 
  762 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
  763         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
  764             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
  765             (var) = (tvar))
  766 
  767 #define TAILQ_INIT(head) do {                                           \
  768         TAILQ_FIRST((head)) = NULL;                                     \
  769         (head)->tqh_last = &TAILQ_FIRST((head));                        \
  770         QMD_TRACE_HEAD(head);                                           \
  771 } while (0)
  772 
  773 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
  774         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
  775         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
  776                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
  777                     &TAILQ_NEXT((elm), field);                          \
  778         else {                                                          \
  779                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
  780                 QMD_TRACE_HEAD(head);                                   \
  781         }                                                               \
  782         TAILQ_NEXT((listelm), field) = (elm);                           \
  783         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
  784         QMD_TRACE_ELEM(&(elm)->field);                                  \
  785         QMD_TRACE_ELEM(&(listelm)->field);                              \
  786 } while (0)
  787 
  788 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
  789         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
  790         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
  791         TAILQ_NEXT((elm), field) = (listelm);                           \
  792         *(listelm)->field.tqe_prev = (elm);                             \
  793         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
  794         QMD_TRACE_ELEM(&(elm)->field);                                  \
  795         QMD_TRACE_ELEM(&(listelm)->field);                              \
  796 } while (0)
  797 
  798 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
  799         QMD_TAILQ_CHECK_HEAD(head, field);                              \
  800         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
  801                 TAILQ_FIRST((head))->field.tqe_prev =                   \
  802                     &TAILQ_NEXT((elm), field);                          \
  803         else                                                            \
  804                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
  805         TAILQ_FIRST((head)) = (elm);                                    \
  806         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
  807         QMD_TRACE_HEAD(head);                                           \
  808         QMD_TRACE_ELEM(&(elm)->field);                                  \
  809 } while (0)
  810 
  811 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
  812         QMD_TAILQ_CHECK_TAIL(head, field);                              \
  813         TAILQ_NEXT((elm), field) = NULL;                                \
  814         (elm)->field.tqe_prev = (head)->tqh_last;                       \
  815         *(head)->tqh_last = (elm);                                      \
  816         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
  817         QMD_TRACE_HEAD(head);                                           \
  818         QMD_TRACE_ELEM(&(elm)->field);                                  \
  819 } while (0)
  820 
  821 #define TAILQ_LAST(head, headname)                                      \
  822         (*(((struct headname *)((head)->tqh_last))->tqh_last))
  823 
  824 /*
  825  * The FAST function is fast in that it causes no data access other
  826  * then the access to the head. The standard LAST function above
  827  * will cause a data access of both the element you want and
  828  * the previous element. FAST is very useful for instances when
  829  * you may want to prefetch the last data element.
  830  */
  831 #define TAILQ_LAST_FAST(head, type, field)                      \
  832     (TAILQ_EMPTY(head) ? NULL : __containerof((head)->tqh_last, QUEUE_TYPEOF(type), field.tqe_next))
  833 
  834 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
  835 
  836 #define TAILQ_PREV(elm, headname, field)                                \
  837         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
  838 
  839 #define TAILQ_PREV_FAST(elm, head, type, field)                         \
  840     ((elm)->field.tqe_prev == &(head)->tqh_first ? NULL :               \
  841      __containerof((elm)->field.tqe_prev, QUEUE_TYPEOF(type), field.tqe_next))
  842 
  843 #define TAILQ_REMOVE(head, elm, field) do {                             \
  844         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
  845         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
  846         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
  847         QMD_TAILQ_CHECK_PREV(elm, field);                               \
  848         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
  849                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
  850                     (elm)->field.tqe_prev;                              \
  851         else {                                                          \
  852                 (head)->tqh_last = (elm)->field.tqe_prev;               \
  853                 QMD_TRACE_HEAD(head);                                   \
  854         }                                                               \
  855         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
  856         TRASHIT(*oldnext);                                              \
  857         TRASHIT(*oldprev);                                              \
  858         QMD_TRACE_ELEM(&(elm)->field);                                  \
  859 } while (0)
  860 
  861 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
  862         QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
  863         QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
  864         (head1)->tqh_first = (head2)->tqh_first;                        \
  865         (head1)->tqh_last = (head2)->tqh_last;                          \
  866         (head2)->tqh_first = swap_first;                                \
  867         (head2)->tqh_last = swap_last;                                  \
  868         if ((swap_first = (head1)->tqh_first) != NULL)                  \
  869                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
  870         else                                                            \
  871                 (head1)->tqh_last = &(head1)->tqh_first;                \
  872         if ((swap_first = (head2)->tqh_first) != NULL)                  \
  873                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
  874         else                                                            \
  875                 (head2)->tqh_last = &(head2)->tqh_first;                \
  876 } while (0)
  877 
  878 #define TAILQ_END(head)         NULL
  879 
  880 #endif /* !_SYS_QUEUE_H_ */

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