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: releng/12.0/sys/sys/queue.h 334804 2018-06-07 18:18:13Z rrs $
   33  */
   34 
   35 #ifndef _SYS_QUEUE_H_
   36 #define _SYS_QUEUE_H_
   37 
   38 #include <sys/cdefs.h>
   39 
   40 /*
   41  * This file defines four types of data structures: singly-linked lists,
   42  * singly-linked tail queues, lists and tail queues.
   43  *
   44  * A singly-linked list is headed by a single forward pointer. The elements
   45  * are singly linked for minimum space and pointer manipulation overhead at
   46  * the expense of O(n) removal for arbitrary elements. New elements can be
   47  * added to the list after an existing element or at the head of the list.
   48  * Elements being removed from the head of the list should use the explicit
   49  * macro for this purpose for optimum efficiency. A singly-linked list may
   50  * only be traversed in the forward direction.  Singly-linked lists are ideal
   51  * for applications with large datasets and few or no removals or for
   52  * implementing a LIFO queue.
   53  *
   54  * A singly-linked tail queue is headed by a pair of pointers, one to the
   55  * head of the list and the other to the tail of the list. The elements are
   56  * singly linked for minimum space and pointer manipulation overhead at the
   57  * expense of O(n) removal for arbitrary elements. New elements can be added
   58  * to the list after an existing element, at the head of the list, or at the
   59  * end of the list. Elements being removed from the head of the tail queue
   60  * should use the explicit macro for this purpose for optimum efficiency.
   61  * A singly-linked tail queue may only be traversed in the forward direction.
   62  * Singly-linked tail queues are ideal for applications with large datasets
   63  * and few or no removals or for implementing a FIFO queue.
   64  *
   65  * A list is headed by a single forward pointer (or an array of forward
   66  * pointers for a hash table header). The elements are doubly linked
   67  * so that an arbitrary element can be removed without a need to
   68  * traverse the list. New elements can be added to the list before
   69  * or after an existing element or at the head of the list. A list
   70  * may be traversed in either direction.
   71  *
   72  * A tail queue is headed by a pair of pointers, one to the head of the
   73  * list and the other to the tail of the list. The elements are doubly
   74  * linked so that an arbitrary element can be removed without a need to
   75  * traverse the list. New elements can be added to the list before or
   76  * after an existing element, at the head of the list, or at the end of
   77  * the list. A tail queue may be traversed in either direction.
   78  *
   79  * For details on the use of these macros, see the queue(3) manual page.
   80  *
   81  * Below is a summary of implemented functions where:
   82  *  +  means the macro is available
   83  *  -  means the macro is not available
   84  *  s  means the macro is available but is slow (runs in O(n) time)
   85  *
   86  *                              SLIST   LIST    STAILQ  TAILQ
   87  * _HEAD                        +       +       +       +
   88  * _CLASS_HEAD                  +       +       +       +
   89  * _HEAD_INITIALIZER            +       +       +       +
   90  * _ENTRY                       +       +       +       +
   91  * _CLASS_ENTRY                 +       +       +       +
   92  * _INIT                        +       +       +       +
   93  * _EMPTY                       +       +       +       +
   94  * _FIRST                       +       +       +       +
   95  * _NEXT                        +       +       +       +
   96  * _PREV                        -       +       -       +
   97  * _LAST                        -       -       +       +
   98  * _LAST_FAST                   -       -       -       +
   99  * _FOREACH                     +       +       +       +
  100  * _FOREACH_FROM                +       +       +       +
  101  * _FOREACH_SAFE                +       +       +       +
  102  * _FOREACH_FROM_SAFE           +       +       +       +
  103  * _FOREACH_REVERSE             -       -       -       +
  104  * _FOREACH_REVERSE_FROM        -       -       -       +
  105  * _FOREACH_REVERSE_SAFE        -       -       -       +
  106  * _FOREACH_REVERSE_FROM_SAFE   -       -       -       +
  107  * _INSERT_HEAD                 +       +       +       +
  108  * _INSERT_BEFORE               -       +       -       +
  109  * _INSERT_AFTER                +       +       +       +
  110  * _INSERT_TAIL                 -       -       +       +
  111  * _CONCAT                      s       s       +       +
  112  * _REMOVE_AFTER                +       -       +       -
  113  * _REMOVE_HEAD                 +       -       +       -
  114  * _REMOVE                      s       +       s       +
  115  * _SWAP                        +       +       +       +
  116  *
  117  */
  118 #ifdef QUEUE_MACRO_DEBUG
  119 #warn Use QUEUE_MACRO_DEBUG_TRACE and/or QUEUE_MACRO_DEBUG_TRASH
  120 #define QUEUE_MACRO_DEBUG_TRACE
  121 #define QUEUE_MACRO_DEBUG_TRASH
  122 #endif
  123 
  124 #ifdef QUEUE_MACRO_DEBUG_TRACE
  125 /* Store the last 2 places the queue element or head was altered */
  126 struct qm_trace {
  127         unsigned long    lastline;
  128         unsigned long    prevline;
  129         const char      *lastfile;
  130         const char      *prevfile;
  131 };
  132 
  133 #define TRACEBUF        struct qm_trace trace;
  134 #define TRACEBUF_INITIALIZER    { __LINE__, 0, __FILE__, NULL } ,
  135 
  136 #define QMD_TRACE_HEAD(head) do {                                       \
  137         (head)->trace.prevline = (head)->trace.lastline;                \
  138         (head)->trace.prevfile = (head)->trace.lastfile;                \
  139         (head)->trace.lastline = __LINE__;                              \
  140         (head)->trace.lastfile = __FILE__;                              \
  141 } while (0)
  142 
  143 #define QMD_TRACE_ELEM(elem) do {                                       \
  144         (elem)->trace.prevline = (elem)->trace.lastline;                \
  145         (elem)->trace.prevfile = (elem)->trace.lastfile;                \
  146         (elem)->trace.lastline = __LINE__;                              \
  147         (elem)->trace.lastfile = __FILE__;                              \
  148 } while (0)
  149 
  150 #else   /* !QUEUE_MACRO_DEBUG_TRACE */
  151 #define QMD_TRACE_ELEM(elem)
  152 #define QMD_TRACE_HEAD(head)
  153 #define TRACEBUF
  154 #define TRACEBUF_INITIALIZER
  155 #endif  /* QUEUE_MACRO_DEBUG_TRACE */
  156 
  157 #ifdef QUEUE_MACRO_DEBUG_TRASH
  158 #define TRASHIT(x)              do {(x) = (void *)-1;} while (0)
  159 #define QMD_IS_TRASHED(x)       ((x) == (void *)(intptr_t)-1)
  160 #else   /* !QUEUE_MACRO_DEBUG_TRASH */
  161 #define TRASHIT(x)
  162 #define QMD_IS_TRASHED(x)       0
  163 #endif  /* QUEUE_MACRO_DEBUG_TRASH */
  164 
  165 #if defined(QUEUE_MACRO_DEBUG_TRACE) || defined(QUEUE_MACRO_DEBUG_TRASH)
  166 #define QMD_SAVELINK(name, link)        void **name = (void *)&(link)
  167 #else   /* !QUEUE_MACRO_DEBUG_TRACE && !QUEUE_MACRO_DEBUG_TRASH */
  168 #define QMD_SAVELINK(name, link)
  169 #endif  /* QUEUE_MACRO_DEBUG_TRACE || QUEUE_MACRO_DEBUG_TRASH */
  170 
  171 #ifdef __cplusplus
  172 /*
  173  * In C++ there can be structure lists and class lists:
  174  */
  175 #define QUEUE_TYPEOF(type) type
  176 #else
  177 #define QUEUE_TYPEOF(type) struct type
  178 #endif
  179 
  180 /*
  181  * Singly-linked List declarations.
  182  */
  183 #define SLIST_HEAD(name, type)                                          \
  184 struct name {                                                           \
  185         struct type *slh_first; /* first element */                     \
  186 }
  187 
  188 #define SLIST_CLASS_HEAD(name, type)                                    \
  189 struct name {                                                           \
  190         class type *slh_first;  /* first element */                     \
  191 }
  192 
  193 #define SLIST_HEAD_INITIALIZER(head)                                    \
  194         { NULL }
  195 
  196 #define SLIST_ENTRY(type)                                               \
  197 struct {                                                                \
  198         struct type *sle_next;  /* next element */                      \
  199 }
  200 
  201 #define SLIST_CLASS_ENTRY(type)                                         \
  202 struct {                                                                \
  203         class type *sle_next;           /* next element */              \
  204 }
  205 
  206 /*
  207  * Singly-linked List functions.
  208  */
  209 #if (defined(_KERNEL) && defined(INVARIANTS))
  210 #define QMD_SLIST_CHECK_PREVPTR(prevp, elm) do {                        \
  211         if (*(prevp) != (elm))                                          \
  212                 panic("Bad prevptr *(%p) == %p != %p",                  \
  213                     (prevp), *(prevp), (elm));                          \
  214 } while (0)
  215 #else
  216 #define QMD_SLIST_CHECK_PREVPTR(prevp, elm)
  217 #endif
  218 
  219 #define SLIST_CONCAT(head1, head2, type, field) do {                    \
  220         QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head1);                \
  221         if (curelm == NULL) {                                           \
  222                 if ((SLIST_FIRST(head1) = SLIST_FIRST(head2)) != NULL)  \
  223                         SLIST_INIT(head2);                              \
  224         } else if (SLIST_FIRST(head2) != NULL) {                        \
  225                 while (SLIST_NEXT(curelm, field) != NULL)               \
  226                         curelm = SLIST_NEXT(curelm, field);             \
  227                 SLIST_NEXT(curelm, field) = SLIST_FIRST(head2);         \
  228                 SLIST_INIT(head2);                                      \
  229         }                                                               \
  230 } while (0)
  231 
  232 #define SLIST_EMPTY(head)       ((head)->slh_first == NULL)
  233 
  234 #define SLIST_FIRST(head)       ((head)->slh_first)
  235 
  236 #define SLIST_FOREACH(var, head, field)                                 \
  237         for ((var) = SLIST_FIRST((head));                               \
  238             (var);                                                      \
  239             (var) = SLIST_NEXT((var), field))
  240 
  241 #define SLIST_FOREACH_FROM(var, head, field)                            \
  242         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
  243             (var);                                                      \
  244             (var) = SLIST_NEXT((var), field))
  245 
  246 #define SLIST_FOREACH_SAFE(var, head, field, tvar)                      \
  247         for ((var) = SLIST_FIRST((head));                               \
  248             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
  249             (var) = (tvar))
  250 
  251 #define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
  252         for ((var) = ((var) ? (var) : SLIST_FIRST((head)));             \
  253             (var) && ((tvar) = SLIST_NEXT((var), field), 1);            \
  254             (var) = (tvar))
  255 
  256 #define SLIST_FOREACH_PREVPTR(var, varp, head, field)                   \
  257         for ((varp) = &SLIST_FIRST((head));                             \
  258             ((var) = *(varp)) != NULL;                                  \
  259             (varp) = &SLIST_NEXT((var), field))
  260 
  261 #define SLIST_INIT(head) do {                                           \
  262         SLIST_FIRST((head)) = NULL;                                     \
  263 } while (0)
  264 
  265 #define SLIST_INSERT_AFTER(slistelm, elm, field) do {                   \
  266         SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);       \
  267         SLIST_NEXT((slistelm), field) = (elm);                          \
  268 } while (0)
  269 
  270 #define SLIST_INSERT_HEAD(head, elm, field) do {                        \
  271         SLIST_NEXT((elm), field) = SLIST_FIRST((head));                 \
  272         SLIST_FIRST((head)) = (elm);                                    \
  273 } while (0)
  274 
  275 #define SLIST_NEXT(elm, field)  ((elm)->field.sle_next)
  276 
  277 #define SLIST_REMOVE(head, elm, type, field) do {                       \
  278         QMD_SAVELINK(oldnext, (elm)->field.sle_next);                   \
  279         if (SLIST_FIRST((head)) == (elm)) {                             \
  280                 SLIST_REMOVE_HEAD((head), field);                       \
  281         }                                                               \
  282         else {                                                          \
  283                 QUEUE_TYPEOF(type) *curelm = SLIST_FIRST(head);         \
  284                 while (SLIST_NEXT(curelm, field) != (elm))              \
  285                         curelm = SLIST_NEXT(curelm, field);             \
  286                 SLIST_REMOVE_AFTER(curelm, field);                      \
  287         }                                                               \
  288         TRASHIT(*oldnext);                                              \
  289 } while (0)
  290 
  291 #define SLIST_REMOVE_AFTER(elm, field) do {                             \
  292         SLIST_NEXT(elm, field) =                                        \
  293             SLIST_NEXT(SLIST_NEXT(elm, field), field);                  \
  294 } while (0)
  295 
  296 #define SLIST_REMOVE_HEAD(head, field) do {                             \
  297         SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);   \
  298 } while (0)
  299 
  300 #define SLIST_REMOVE_PREVPTR(prevp, elm, field) do {                    \
  301         QMD_SLIST_CHECK_PREVPTR(prevp, elm);                            \
  302         *(prevp) = SLIST_NEXT(elm, field);                              \
  303         TRASHIT((elm)->field.sle_next);                                 \
  304 } while (0)
  305 
  306 #define SLIST_SWAP(head1, head2, type) do {                             \
  307         QUEUE_TYPEOF(type) *swap_first = SLIST_FIRST(head1);            \
  308         SLIST_FIRST(head1) = SLIST_FIRST(head2);                        \
  309         SLIST_FIRST(head2) = swap_first;                                \
  310 } while (0)
  311 
  312 /*
  313  * Singly-linked Tail queue declarations.
  314  */
  315 #define STAILQ_HEAD(name, type)                                         \
  316 struct name {                                                           \
  317         struct type *stqh_first;/* first element */                     \
  318         struct type **stqh_last;/* addr of last next element */         \
  319 }
  320 
  321 #define STAILQ_CLASS_HEAD(name, type)                                   \
  322 struct name {                                                           \
  323         class type *stqh_first; /* first element */                     \
  324         class type **stqh_last; /* addr of last next element */         \
  325 }
  326 
  327 #define STAILQ_HEAD_INITIALIZER(head)                                   \
  328         { NULL, &(head).stqh_first }
  329 
  330 #define STAILQ_ENTRY(type)                                              \
  331 struct {                                                                \
  332         struct type *stqe_next; /* next element */                      \
  333 }
  334 
  335 #define STAILQ_CLASS_ENTRY(type)                                        \
  336 struct {                                                                \
  337         class type *stqe_next;  /* next element */                      \
  338 }
  339 
  340 /*
  341  * Singly-linked Tail queue functions.
  342  */
  343 #define STAILQ_CONCAT(head1, head2) do {                                \
  344         if (!STAILQ_EMPTY((head2))) {                                   \
  345                 *(head1)->stqh_last = (head2)->stqh_first;              \
  346                 (head1)->stqh_last = (head2)->stqh_last;                \
  347                 STAILQ_INIT((head2));                                   \
  348         }                                                               \
  349 } while (0)
  350 
  351 #define STAILQ_EMPTY(head)      ((head)->stqh_first == NULL)
  352 
  353 #define STAILQ_FIRST(head)      ((head)->stqh_first)
  354 
  355 #define STAILQ_FOREACH(var, head, field)                                \
  356         for((var) = STAILQ_FIRST((head));                               \
  357            (var);                                                       \
  358            (var) = STAILQ_NEXT((var), field))
  359 
  360 #define STAILQ_FOREACH_FROM(var, head, field)                           \
  361         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
  362            (var);                                                       \
  363            (var) = STAILQ_NEXT((var), field))
  364 
  365 #define STAILQ_FOREACH_SAFE(var, head, field, tvar)                     \
  366         for ((var) = STAILQ_FIRST((head));                              \
  367             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
  368             (var) = (tvar))
  369 
  370 #define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                \
  371         for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));            \
  372             (var) && ((tvar) = STAILQ_NEXT((var), field), 1);           \
  373             (var) = (tvar))
  374 
  375 #define STAILQ_INIT(head) do {                                          \
  376         STAILQ_FIRST((head)) = NULL;                                    \
  377         (head)->stqh_last = &STAILQ_FIRST((head));                      \
  378 } while (0)
  379 
  380 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {               \
  381         if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
  382                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
  383         STAILQ_NEXT((tqelm), field) = (elm);                            \
  384 } while (0)
  385 
  386 #define STAILQ_INSERT_HEAD(head, elm, field) do {                       \
  387         if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
  388                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
  389         STAILQ_FIRST((head)) = (elm);                                   \
  390 } while (0)
  391 
  392 #define STAILQ_INSERT_TAIL(head, elm, field) do {                       \
  393         STAILQ_NEXT((elm), field) = NULL;                               \
  394         *(head)->stqh_last = (elm);                                     \
  395         (head)->stqh_last = &STAILQ_NEXT((elm), field);                 \
  396 } while (0)
  397 
  398 #define STAILQ_LAST(head, type, field)                          \
  399         (STAILQ_EMPTY((head)) ? NULL :                          \
  400             __containerof((head)->stqh_last,                    \
  401             QUEUE_TYPEOF(type), field.stqe_next))
  402 
  403 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
  404 
  405 #define STAILQ_REMOVE(head, elm, type, field) do {                      \
  406         QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                  \
  407         if (STAILQ_FIRST((head)) == (elm)) {                            \
  408                 STAILQ_REMOVE_HEAD((head), field);                      \
  409         }                                                               \
  410         else {                                                          \
  411                 QUEUE_TYPEOF(type) *curelm = STAILQ_FIRST(head);        \
  412                 while (STAILQ_NEXT(curelm, field) != (elm))             \
  413                         curelm = STAILQ_NEXT(curelm, field);            \
  414                 STAILQ_REMOVE_AFTER(head, curelm, field);               \
  415         }                                                               \
  416         TRASHIT(*oldnext);                                              \
  417 } while (0)
  418 
  419 #define STAILQ_REMOVE_AFTER(head, elm, field) do {                      \
  420         if ((STAILQ_NEXT(elm, field) =                                  \
  421              STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)      \
  422                 (head)->stqh_last = &STAILQ_NEXT((elm), field);         \
  423 } while (0)
  424 
  425 #define STAILQ_REMOVE_HEAD(head, field) do {                            \
  426         if ((STAILQ_FIRST((head)) =                                     \
  427              STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)         \
  428                 (head)->stqh_last = &STAILQ_FIRST((head));              \
  429 } while (0)
  430 
  431 #define STAILQ_SWAP(head1, head2, type) do {                            \
  432         QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);           \
  433         QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;            \
  434         STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                      \
  435         (head1)->stqh_last = (head2)->stqh_last;                        \
  436         STAILQ_FIRST(head2) = swap_first;                               \
  437         (head2)->stqh_last = swap_last;                                 \
  438         if (STAILQ_EMPTY(head1))                                        \
  439                 (head1)->stqh_last = &STAILQ_FIRST(head1);              \
  440         if (STAILQ_EMPTY(head2))                                        \
  441                 (head2)->stqh_last = &STAILQ_FIRST(head2);              \
  442 } while (0)
  443 
  444 
  445 /*
  446  * List declarations.
  447  */
  448 #define LIST_HEAD(name, type)                                           \
  449 struct name {                                                           \
  450         struct type *lh_first;  /* first element */                     \
  451 }
  452 
  453 #define LIST_CLASS_HEAD(name, type)                                     \
  454 struct name {                                                           \
  455         class type *lh_first;   /* first element */                     \
  456 }
  457 
  458 #define LIST_HEAD_INITIALIZER(head)                                     \
  459         { NULL }
  460 
  461 #define LIST_ENTRY(type)                                                \
  462 struct {                                                                \
  463         struct type *le_next;   /* next element */                      \
  464         struct type **le_prev;  /* address of previous next element */  \
  465 }
  466 
  467 #define LIST_CLASS_ENTRY(type)                                          \
  468 struct {                                                                \
  469         class type *le_next;    /* next element */                      \
  470         class type **le_prev;   /* address of previous next element */  \
  471 }
  472 
  473 /*
  474  * List functions.
  475  */
  476 
  477 #if (defined(_KERNEL) && defined(INVARIANTS))
  478 /*
  479  * QMD_LIST_CHECK_HEAD(LIST_HEAD *head, LIST_ENTRY NAME)
  480  *
  481  * If the list is non-empty, validates that the first element of the list
  482  * points back at 'head.'
  483  */
  484 #define QMD_LIST_CHECK_HEAD(head, field) do {                           \
  485         if (LIST_FIRST((head)) != NULL &&                               \
  486             LIST_FIRST((head))->field.le_prev !=                        \
  487              &LIST_FIRST((head)))                                       \
  488                 panic("Bad list head %p first->prev != head", (head));  \
  489 } while (0)
  490 
  491 /*
  492  * QMD_LIST_CHECK_NEXT(TYPE *elm, LIST_ENTRY NAME)
  493  *
  494  * If an element follows 'elm' in the list, validates that the next element
  495  * points back at 'elm.'
  496  */
  497 #define QMD_LIST_CHECK_NEXT(elm, field) do {                            \
  498         if (LIST_NEXT((elm), field) != NULL &&                          \
  499             LIST_NEXT((elm), field)->field.le_prev !=                   \
  500              &((elm)->field.le_next))                                   \
  501                 panic("Bad link elm %p next->prev != elm", (elm));      \
  502 } while (0)
  503 
  504 /*
  505  * QMD_LIST_CHECK_PREV(TYPE *elm, LIST_ENTRY NAME)
  506  *
  507  * Validates that the previous element (or head of the list) points to 'elm.'
  508  */
  509 #define QMD_LIST_CHECK_PREV(elm, field) do {                            \
  510         if (*(elm)->field.le_prev != (elm))                             \
  511                 panic("Bad link elm %p prev->next != elm", (elm));      \
  512 } while (0)
  513 #else
  514 #define QMD_LIST_CHECK_HEAD(head, field)
  515 #define QMD_LIST_CHECK_NEXT(elm, field)
  516 #define QMD_LIST_CHECK_PREV(elm, field)
  517 #endif /* (_KERNEL && INVARIANTS) */
  518 
  519 #define LIST_CONCAT(head1, head2, type, field) do {                           \
  520         QUEUE_TYPEOF(type) *curelm = LIST_FIRST(head1);                       \
  521         if (curelm == NULL) {                                                 \
  522                 if ((LIST_FIRST(head1) = LIST_FIRST(head2)) != NULL) {        \
  523                         LIST_FIRST(head2)->field.le_prev =                    \
  524                             &LIST_FIRST((head1));                             \
  525                         LIST_INIT(head2);                                     \
  526                 }                                                             \
  527         } else if (LIST_FIRST(head2) != NULL) {                               \
  528                 while (LIST_NEXT(curelm, field) != NULL)                      \
  529                         curelm = LIST_NEXT(curelm, field);                    \
  530                 LIST_NEXT(curelm, field) = LIST_FIRST(head2);                 \
  531                 LIST_FIRST(head2)->field.le_prev = &LIST_NEXT(curelm, field); \
  532                 LIST_INIT(head2);                                             \
  533         }                                                                     \
  534 } while (0)
  535 
  536 #define LIST_EMPTY(head)        ((head)->lh_first == NULL)
  537 
  538 #define LIST_FIRST(head)        ((head)->lh_first)
  539 
  540 #define LIST_FOREACH(var, head, field)                                  \
  541         for ((var) = LIST_FIRST((head));                                \
  542             (var);                                                      \
  543             (var) = LIST_NEXT((var), field))
  544 
  545 #define LIST_FOREACH_FROM(var, head, field)                             \
  546         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
  547             (var);                                                      \
  548             (var) = LIST_NEXT((var), field))
  549 
  550 #define LIST_FOREACH_SAFE(var, head, field, tvar)                       \
  551         for ((var) = LIST_FIRST((head));                                \
  552             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
  553             (var) = (tvar))
  554 
  555 #define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                  \
  556         for ((var) = ((var) ? (var) : LIST_FIRST((head)));              \
  557             (var) && ((tvar) = LIST_NEXT((var), field), 1);             \
  558             (var) = (tvar))
  559 
  560 #define LIST_INIT(head) do {                                            \
  561         LIST_FIRST((head)) = NULL;                                      \
  562 } while (0)
  563 
  564 #define LIST_INSERT_AFTER(listelm, elm, field) do {                     \
  565         QMD_LIST_CHECK_NEXT(listelm, field);                            \
  566         if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
  567                 LIST_NEXT((listelm), field)->field.le_prev =            \
  568                     &LIST_NEXT((elm), field);                           \
  569         LIST_NEXT((listelm), field) = (elm);                            \
  570         (elm)->field.le_prev = &LIST_NEXT((listelm), field);            \
  571 } while (0)
  572 
  573 #define LIST_INSERT_BEFORE(listelm, elm, field) do {                    \
  574         QMD_LIST_CHECK_PREV(listelm, field);                            \
  575         (elm)->field.le_prev = (listelm)->field.le_prev;                \
  576         LIST_NEXT((elm), field) = (listelm);                            \
  577         *(listelm)->field.le_prev = (elm);                              \
  578         (listelm)->field.le_prev = &LIST_NEXT((elm), field);            \
  579 } while (0)
  580 
  581 #define LIST_INSERT_HEAD(head, elm, field) do {                         \
  582         QMD_LIST_CHECK_HEAD((head), field);                             \
  583         if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
  584                 LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
  585         LIST_FIRST((head)) = (elm);                                     \
  586         (elm)->field.le_prev = &LIST_FIRST((head));                     \
  587 } while (0)
  588 
  589 #define LIST_NEXT(elm, field)   ((elm)->field.le_next)
  590 
  591 #define LIST_PREV(elm, head, type, field)                       \
  592         ((elm)->field.le_prev == &LIST_FIRST((head)) ? NULL :   \
  593             __containerof((elm)->field.le_prev,                 \
  594             QUEUE_TYPEOF(type), field.le_next))
  595 
  596 #define LIST_REMOVE(elm, field) do {                                    \
  597         QMD_SAVELINK(oldnext, (elm)->field.le_next);                    \
  598         QMD_SAVELINK(oldprev, (elm)->field.le_prev);                    \
  599         QMD_LIST_CHECK_NEXT(elm, field);                                \
  600         QMD_LIST_CHECK_PREV(elm, field);                                \
  601         if (LIST_NEXT((elm), field) != NULL)                            \
  602                 LIST_NEXT((elm), field)->field.le_prev =                \
  603                     (elm)->field.le_prev;                               \
  604         *(elm)->field.le_prev = LIST_NEXT((elm), field);                \
  605         TRASHIT(*oldnext);                                              \
  606         TRASHIT(*oldprev);                                              \
  607 } while (0)
  608 
  609 #define LIST_SWAP(head1, head2, type, field) do {                       \
  610         QUEUE_TYPEOF(type) *swap_tmp = LIST_FIRST(head1);               \
  611         LIST_FIRST((head1)) = LIST_FIRST((head2));                      \
  612         LIST_FIRST((head2)) = swap_tmp;                                 \
  613         if ((swap_tmp = LIST_FIRST((head1))) != NULL)                   \
  614                 swap_tmp->field.le_prev = &LIST_FIRST((head1));         \
  615         if ((swap_tmp = LIST_FIRST((head2))) != NULL)                   \
  616                 swap_tmp->field.le_prev = &LIST_FIRST((head2));         \
  617 } while (0)
  618 
  619 /*
  620  * Tail queue declarations.
  621  */
  622 #define TAILQ_HEAD(name, type)                                          \
  623 struct name {                                                           \
  624         struct type *tqh_first; /* first element */                     \
  625         struct type **tqh_last; /* addr of last next element */         \
  626         TRACEBUF                                                        \
  627 }
  628 
  629 #define TAILQ_CLASS_HEAD(name, type)                                    \
  630 struct name {                                                           \
  631         class type *tqh_first;  /* first element */                     \
  632         class type **tqh_last;  /* addr of last next element */         \
  633         TRACEBUF                                                        \
  634 }
  635 
  636 #define TAILQ_HEAD_INITIALIZER(head)                                    \
  637         { NULL, &(head).tqh_first, TRACEBUF_INITIALIZER }
  638 
  639 #define TAILQ_ENTRY(type)                                               \
  640 struct {                                                                \
  641         struct type *tqe_next;  /* next element */                      \
  642         struct type **tqe_prev; /* address of previous next element */  \
  643         TRACEBUF                                                        \
  644 }
  645 
  646 #define TAILQ_CLASS_ENTRY(type)                                         \
  647 struct {                                                                \
  648         class type *tqe_next;   /* next element */                      \
  649         class type **tqe_prev;  /* address of previous next element */  \
  650         TRACEBUF                                                        \
  651 }
  652 
  653 /*
  654  * Tail queue functions.
  655  */
  656 #if (defined(_KERNEL) && defined(INVARIANTS))
  657 /*
  658  * QMD_TAILQ_CHECK_HEAD(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
  659  *
  660  * If the tailq is non-empty, validates that the first element of the tailq
  661  * points back at 'head.'
  662  */
  663 #define QMD_TAILQ_CHECK_HEAD(head, field) do {                          \
  664         if (!TAILQ_EMPTY(head) &&                                       \
  665             TAILQ_FIRST((head))->field.tqe_prev !=                      \
  666              &TAILQ_FIRST((head)))                                      \
  667                 panic("Bad tailq head %p first->prev != head", (head)); \
  668 } while (0)
  669 
  670 /*
  671  * QMD_TAILQ_CHECK_TAIL(TAILQ_HEAD *head, TAILQ_ENTRY NAME)
  672  *
  673  * Validates that the tail of the tailq is a pointer to pointer to NULL.
  674  */
  675 #define QMD_TAILQ_CHECK_TAIL(head, field) do {                          \
  676         if (*(head)->tqh_last != NULL)                                  \
  677                 panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));  \
  678 } while (0)
  679 
  680 /*
  681  * QMD_TAILQ_CHECK_NEXT(TYPE *elm, TAILQ_ENTRY NAME)
  682  *
  683  * If an element follows 'elm' in the tailq, validates that the next element
  684  * points back at 'elm.'
  685  */
  686 #define QMD_TAILQ_CHECK_NEXT(elm, field) do {                           \
  687         if (TAILQ_NEXT((elm), field) != NULL &&                         \
  688             TAILQ_NEXT((elm), field)->field.tqe_prev !=                 \
  689              &((elm)->field.tqe_next))                                  \
  690                 panic("Bad link elm %p next->prev != elm", (elm));      \
  691 } while (0)
  692 
  693 /*
  694  * QMD_TAILQ_CHECK_PREV(TYPE *elm, TAILQ_ENTRY NAME)
  695  *
  696  * Validates that the previous element (or head of the tailq) points to 'elm.'
  697  */
  698 #define QMD_TAILQ_CHECK_PREV(elm, field) do {                           \
  699         if (*(elm)->field.tqe_prev != (elm))                            \
  700                 panic("Bad link elm %p prev->next != elm", (elm));      \
  701 } while (0)
  702 #else
  703 #define QMD_TAILQ_CHECK_HEAD(head, field)
  704 #define QMD_TAILQ_CHECK_TAIL(head, headname)
  705 #define QMD_TAILQ_CHECK_NEXT(elm, field)
  706 #define QMD_TAILQ_CHECK_PREV(elm, field)
  707 #endif /* (_KERNEL && INVARIANTS) */
  708 
  709 #define TAILQ_CONCAT(head1, head2, field) do {                          \
  710         if (!TAILQ_EMPTY(head2)) {                                      \
  711                 *(head1)->tqh_last = (head2)->tqh_first;                \
  712                 (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
  713                 (head1)->tqh_last = (head2)->tqh_last;                  \
  714                 TAILQ_INIT((head2));                                    \
  715                 QMD_TRACE_HEAD(head1);                                  \
  716                 QMD_TRACE_HEAD(head2);                                  \
  717         }                                                               \
  718 } while (0)
  719 
  720 #define TAILQ_EMPTY(head)       ((head)->tqh_first == NULL)
  721 
  722 #define TAILQ_FIRST(head)       ((head)->tqh_first)
  723 
  724 #define TAILQ_FOREACH(var, head, field)                                 \
  725         for ((var) = TAILQ_FIRST((head));                               \
  726             (var);                                                      \
  727             (var) = TAILQ_NEXT((var), field))
  728 
  729 #define TAILQ_FOREACH_FROM(var, head, field)                            \
  730         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
  731             (var);                                                      \
  732             (var) = TAILQ_NEXT((var), field))
  733 
  734 #define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
  735         for ((var) = TAILQ_FIRST((head));                               \
  736             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
  737             (var) = (tvar))
  738 
  739 #define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                 \
  740         for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));             \
  741             (var) && ((tvar) = TAILQ_NEXT((var), field), 1);            \
  742             (var) = (tvar))
  743 
  744 #define TAILQ_FOREACH_REVERSE(var, head, headname, field)               \
  745         for ((var) = TAILQ_LAST((head), headname);                      \
  746             (var);                                                      \
  747             (var) = TAILQ_PREV((var), headname, field))
  748 
  749 #define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)          \
  750         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
  751             (var);                                                      \
  752             (var) = TAILQ_PREV((var), headname, field))
  753 
  754 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)    \
  755         for ((var) = TAILQ_LAST((head), headname);                      \
  756             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
  757             (var) = (tvar))
  758 
  759 #define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar) \
  760         for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));    \
  761             (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);  \
  762             (var) = (tvar))
  763 
  764 #define TAILQ_INIT(head) do {                                           \
  765         TAILQ_FIRST((head)) = NULL;                                     \
  766         (head)->tqh_last = &TAILQ_FIRST((head));                        \
  767         QMD_TRACE_HEAD(head);                                           \
  768 } while (0)
  769 
  770 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do {              \
  771         QMD_TAILQ_CHECK_NEXT(listelm, field);                           \
  772         if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
  773                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
  774                     &TAILQ_NEXT((elm), field);                          \
  775         else {                                                          \
  776                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
  777                 QMD_TRACE_HEAD(head);                                   \
  778         }                                                               \
  779         TAILQ_NEXT((listelm), field) = (elm);                           \
  780         (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);          \
  781         QMD_TRACE_ELEM(&(elm)->field);                                  \
  782         QMD_TRACE_ELEM(&(listelm)->field);                              \
  783 } while (0)
  784 
  785 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do {                   \
  786         QMD_TAILQ_CHECK_PREV(listelm, field);                           \
  787         (elm)->field.tqe_prev = (listelm)->field.tqe_prev;              \
  788         TAILQ_NEXT((elm), field) = (listelm);                           \
  789         *(listelm)->field.tqe_prev = (elm);                             \
  790         (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);          \
  791         QMD_TRACE_ELEM(&(elm)->field);                                  \
  792         QMD_TRACE_ELEM(&(listelm)->field);                              \
  793 } while (0)
  794 
  795 #define TAILQ_INSERT_HEAD(head, elm, field) do {                        \
  796         QMD_TAILQ_CHECK_HEAD(head, field);                              \
  797         if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)   \
  798                 TAILQ_FIRST((head))->field.tqe_prev =                   \
  799                     &TAILQ_NEXT((elm), field);                          \
  800         else                                                            \
  801                 (head)->tqh_last = &TAILQ_NEXT((elm), field);           \
  802         TAILQ_FIRST((head)) = (elm);                                    \
  803         (elm)->field.tqe_prev = &TAILQ_FIRST((head));                   \
  804         QMD_TRACE_HEAD(head);                                           \
  805         QMD_TRACE_ELEM(&(elm)->field);                                  \
  806 } while (0)
  807 
  808 #define TAILQ_INSERT_TAIL(head, elm, field) do {                        \
  809         QMD_TAILQ_CHECK_TAIL(head, field);                              \
  810         TAILQ_NEXT((elm), field) = NULL;                                \
  811         (elm)->field.tqe_prev = (head)->tqh_last;                       \
  812         *(head)->tqh_last = (elm);                                      \
  813         (head)->tqh_last = &TAILQ_NEXT((elm), field);                   \
  814         QMD_TRACE_HEAD(head);                                           \
  815         QMD_TRACE_ELEM(&(elm)->field);                                  \
  816 } while (0)
  817 
  818 #define TAILQ_LAST(head, headname)                                      \
  819         (*(((struct headname *)((head)->tqh_last))->tqh_last))
  820 
  821 /*
  822  * The FAST function is fast in that it causes no data access other
  823  * then the access to the head. The standard LAST function above
  824  * will cause a data access of both the element you want and 
  825  * the previous element. FAST is very useful for instances when
  826  * you may want to prefetch the last data element.
  827  */
  828 #define TAILQ_LAST_FAST(head, type, field)                      \
  829     (TAILQ_EMPTY(head) ? NULL : __containerof((head)->tqh_last, QUEUE_TYPEOF(type), field.tqe_next))
  830 
  831 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
  832 
  833 #define TAILQ_PREV(elm, headname, field)                                \
  834         (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
  835 
  836 #define TAILQ_REMOVE(head, elm, field) do {                             \
  837         QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                   \
  838         QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                   \
  839         QMD_TAILQ_CHECK_NEXT(elm, field);                               \
  840         QMD_TAILQ_CHECK_PREV(elm, field);                               \
  841         if ((TAILQ_NEXT((elm), field)) != NULL)                         \
  842                 TAILQ_NEXT((elm), field)->field.tqe_prev =              \
  843                     (elm)->field.tqe_prev;                              \
  844         else {                                                          \
  845                 (head)->tqh_last = (elm)->field.tqe_prev;               \
  846                 QMD_TRACE_HEAD(head);                                   \
  847         }                                                               \
  848         *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);              \
  849         TRASHIT(*oldnext);                                              \
  850         TRASHIT(*oldprev);                                              \
  851         QMD_TRACE_ELEM(&(elm)->field);                                  \
  852 } while (0)
  853 
  854 #define TAILQ_SWAP(head1, head2, type, field) do {                      \
  855         QUEUE_TYPEOF(type) *swap_first = (head1)->tqh_first;            \
  856         QUEUE_TYPEOF(type) **swap_last = (head1)->tqh_last;             \
  857         (head1)->tqh_first = (head2)->tqh_first;                        \
  858         (head1)->tqh_last = (head2)->tqh_last;                          \
  859         (head2)->tqh_first = swap_first;                                \
  860         (head2)->tqh_last = swap_last;                                  \
  861         if ((swap_first = (head1)->tqh_first) != NULL)                  \
  862                 swap_first->field.tqe_prev = &(head1)->tqh_first;       \
  863         else                                                            \
  864                 (head1)->tqh_last = &(head1)->tqh_first;                \
  865         if ((swap_first = (head2)->tqh_first) != NULL)                  \
  866                 swap_first->field.tqe_prev = &(head2)->tqh_first;       \
  867         else                                                            \
  868                 (head2)->tqh_last = &(head2)->tqh_first;                \
  869 } while (0)
  870 
  871 #endif /* !_SYS_QUEUE_H_ */

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