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bsd_queue.h
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1 /*-
2  * (c) 1991, 1993
3  * The Regents of the University of California. All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  * notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  * notice, this list of conditions and the following disclaimer in the
12  * documentation and/or other materials provided with the distribution.
13  * 4. Neither the name of the University nor the names of its contributors
14  * may be used to endorse or promote products derived from this software
15  * without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * @(#)queue.h 8.5 (Berkeley) 8/20/94
30  * $FreeBSD: src/sys/sys/queue.h,v 1.68.2.1.2.1 2010/02/10 00:26:20 kensmith Exp $
31  */
32 
33 #ifndef _SYS_QUEUE_H_
34 #define _SYS_QUEUE_H_
35 
36 // #include <sys/cdefs.h>
37 
38 /*
39  * This file defines four types of data structures: singly-linked lists,
40  * singly-linked tail queues, lists and tail queues.
41  *
42  * A singly-linked list is headed by a single forward pointer. The elements
43  * are singly linked for minimum space and pointer manipulation overhead at
44  * the expense of O(n) removal for arbitrary elements. New elements can be
45  * added to the list after an existing element or at the head of the list.
46  * Elements being removed from the head of the list should use the explicit
47  * macro for this purpose for optimum efficiency. A singly-linked list may
48  * only be traversed in the forward direction. Singly-linked lists are ideal
49  * for applications with large datasets and few or no removals or for
50  * implementing a LIFO queue.
51  *
52  * A singly-linked tail queue is headed by a pair of pointers, one to the
53  * head of the list and the other to the tail of the list. The elements are
54  * singly linked for minimum space and pointer manipulation overhead at the
55  * expense of O(n) removal for arbitrary elements. New elements can be added
56  * to the list after an existing element, at the head of the list, or at the
57  * end of the list. Elements being removed from the head of the tail queue
58  * should use the explicit macro for this purpose for optimum efficiency.
59  * A singly-linked tail queue may only be traversed in the forward direction.
60  * Singly-linked tail queues are ideal for applications with large datasets
61  * and few or no removals or for implementing a FIFO queue.
62  *
63  * A list is headed by a single forward pointer (or an array of forward
64  * pointers for a hash table header). The elements are doubly linked
65  * so that an arbitrary element can be removed without a need to
66  * traverse the list. New elements can be added to the list before
67  * or after an existing element or at the head of the list. A list
68  * may only be traversed in the forward direction.
69  *
70  * A tail queue is headed by a pair of pointers, one to the head of the
71  * list and the other to the tail of the list. The elements are doubly
72  * linked so that an arbitrary element can be removed without a need to
73  * traverse the list. New elements can be added to the list before or
74  * after an existing element, at the head of the list, or at the end of
75  * the list. A tail queue may be traversed in either direction.
76  *
77  * For details on the use of these macros, see the queue(3) manual page.
78  *
79  *
80  * SLLIST LIST STAILQ TAILQ
81  * _HEAD + + + +
82  * _HEAD_INITIALIZER + + + +
83  * _ENTRY + + + +
84  * _INIT + + + +
85  * _EMPTY + + + +
86  * _FIRST + + + +
87  * _NEXT + + + +
88  * _PREV - - - +
89  * _LAST - - + +
90  * _FOREACH + + + +
91  * _FOREACH_SAFE + + + +
92  * _FOREACH_REVERSE - - - +
93  * _FOREACH_REVERSE_SAFE - - - +
94  * _INSERT_HEAD + + + +
95  * _INSERT_BEFORE - + - +
96  * _INSERT_AFTER + + + +
97  * _INSERT_TAIL - - + +
98  * _CONCAT - - + +
99  * _REMOVE_AFTER + - + -
100  * _REMOVE_HEAD + - + -
101  * _REMOVE + + + +
102  *
103  */
104 #ifdef QUEUE_MACRO_DEBUG
105 /* Store the last 2 places the queue element or head was altered */
106 struct qm_trace {
107  char * lastfile;
108  int lastline;
109  char * prevfile;
110  int prevline;
111 };
112 
113 #define TRACEBUF struct qm_trace trace;
114 #define TRASHIT(x) do {(x) = (void *)-1;} while (0)
115 
116 #define QMD_TRACE_HEAD(head) do { \
117  (head)->trace.prevline = (head)->trace.lastline; \
118  (head)->trace.prevfile = (head)->trace.lastfile; \
119  (head)->trace.lastline = __LINE__; \
120  (head)->trace.lastfile = __FILE__; \
121 } while (0)
122 
123 #define QMD_TRACE_ELEM(elem) do { \
124  (elem)->trace.prevline = (elem)->trace.lastline; \
125  (elem)->trace.prevfile = (elem)->trace.lastfile; \
126  (elem)->trace.lastline = __LINE__; \
127  (elem)->trace.lastfile = __FILE__; \
128 } while (0)
129 
130 #else
131 #define QMD_TRACE_ELEM(elem)
132 #define QMD_TRACE_HEAD(head)
133 #define TRACEBUF
134 #define TRASHIT(x)
135 #endif /* QUEUE_MACRO_DEBUG */
136 
137 /*
138  * Singly-linked List declarations.
139  */
140 #define SLLIST_HEAD(name, type) \
141 struct name { \
142  struct type *slh_first; /* first element */ \
143 }
144 
145 #define SLLIST_HEAD_INITIALIZER(head) \
146  { NULL }
147 
148 #define SLLIST_ENTRY(type) \
149 struct { \
150  struct type *sle_next; /* next element */ \
151 }
152 
153 /*
154  * Singly-linked List functions.
155  */
156 #define SLLIST_EMPTY(head) ((head)->slh_first == NULL)
157 
158 #define SLLIST_FIRST(head) ((head)->slh_first)
159 
160 #define SLLIST_FOREACH(var, head, field) \
161  for ((var) = SLLIST_FIRST((head)); \
162  (var); \
163  (var) = SLLIST_NEXT((var), field))
164 
165 #define SLLIST_FOREACH_SAFE(var, head, field, tvar) \
166  for ((var) = SLLIST_FIRST((head)); \
167  (var) && ((tvar) = SLLIST_NEXT((var), field), 1); \
168  (var) = (tvar))
169 
170 #define SLLIST_FOREACH_PREVPTR(var, varp, head, field) \
171  for ((varp) = &SLLIST_FIRST((head)); \
172  ((var) = *(varp)) != NULL; \
173  (varp) = &SLLIST_NEXT((var), field))
174 
175 #define SLLIST_INIT(head) do { \
176  SLLIST_FIRST((head)) = NULL; \
177 } while (0)
178 
179 #define SLLIST_INSERT_AFTER(slistelm, elm, field) do { \
180  SLLIST_NEXT((elm), field) = SLLIST_NEXT((slistelm), field); \
181  SLLIST_NEXT((slistelm), field) = (elm); \
182 } while (0)
183 
184 #define SLLIST_INSERT_HEAD(head, elm, field) do { \
185  SLLIST_NEXT((elm), field) = SLLIST_FIRST((head)); \
186  SLLIST_FIRST((head)) = (elm); \
187 } while (0)
188 
189 #define SLLIST_NEXT(elm, field) ((elm)->field.sle_next)
190 
191 #define SLLIST_REMOVE(head, elm, type, field) do { \
192  if (SLLIST_FIRST((head)) == (elm)) { \
193  SLLIST_REMOVE_HEAD((head), field); \
194  } \
195  else { \
196  struct type *curelm = SLLIST_FIRST((head)); \
197  while (SLLIST_NEXT(curelm, field) != (elm)) \
198  curelm = SLLIST_NEXT(curelm, field); \
199  SLLIST_REMOVE_AFTER(curelm, field); \
200  } \
201  TRASHIT((elm)->field.sle_next); \
202 } while (0)
203 
204 #define SLLIST_REMOVE_AFTER(elm, field) do { \
205  SLLIST_NEXT(elm, field) = \
206  SLLIST_NEXT(SLLIST_NEXT(elm, field), field); \
207 } while (0)
208 
209 #define SLLIST_REMOVE_HEAD(head, field) do { \
210  SLLIST_FIRST((head)) = SLLIST_NEXT(SLLIST_FIRST((head)), field); \
211 } while (0)
212 
213 /*
214  * Singly-linked Tail queue declarations.
215  */
216 #define STAILQ_HEAD(name, type) \
217 struct name { \
218  struct type *stqh_first;/* first element */ \
219  struct type **stqh_last;/* addr of last next element */ \
220 }
221 
222 #define STAILQ_HEAD_INITIALIZER(head) \
223  { NULL, &(head).stqh_first }
224 
225 #define STAILQ_ENTRY(type) \
226 struct { \
227  struct type *stqe_next; /* next element */ \
228 }
229 
230 /*
231  * Singly-linked Tail queue functions.
232  */
233 #define STAILQ_CONCAT(head1, head2) do { \
234  if (!STAILQ_EMPTY((head2))) { \
235  *(head1)->stqh_last = (head2)->stqh_first; \
236  (head1)->stqh_last = (head2)->stqh_last; \
237  STAILQ_INIT((head2)); \
238  } \
239 } while (0)
240 
241 #define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)
242 
243 #define STAILQ_FIRST(head) ((head)->stqh_first)
244 
245 #define STAILQ_FOREACH(var, head, field) \
246  for((var) = STAILQ_FIRST((head)); \
247  (var); \
248  (var) = STAILQ_NEXT((var), field))
249 
250 
251 #define STAILQ_FOREACH_SAFE(var, head, field, tvar) \
252  for ((var) = STAILQ_FIRST((head)); \
253  (var) && ((tvar) = STAILQ_NEXT((var), field), 1); \
254  (var) = (tvar))
255 
256 #define STAILQ_INIT(head) do { \
257  STAILQ_FIRST((head)) = NULL; \
258  (head)->stqh_last = &STAILQ_FIRST((head)); \
259 } while (0)
260 
261 #define STAILQ_INSERT_AFTER(head, tqelm, elm, field) do { \
262  if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
263  (head)->stqh_last = &STAILQ_NEXT((elm), field); \
264  STAILQ_NEXT((tqelm), field) = (elm); \
265 } while (0)
266 
267 #define STAILQ_INSERT_HEAD(head, elm, field) do { \
268  if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
269  (head)->stqh_last = &STAILQ_NEXT((elm), field); \
270  STAILQ_FIRST((head)) = (elm); \
271 } while (0)
272 
273 #define STAILQ_INSERT_TAIL(head, elm, field) do { \
274  STAILQ_NEXT((elm), field) = NULL; \
275  *(head)->stqh_last = (elm); \
276  (head)->stqh_last = &STAILQ_NEXT((elm), field); \
277 } while (0)
278 
279 #define STAILQ_LAST(head, type, field) \
280  (STAILQ_EMPTY((head)) ? \
281  NULL : \
282  ((struct type *)(void *) \
283  ((char *)((head)->stqh_last) - __offsetof(struct type, field))))
284 
285 #define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)
286 
287 #define STAILQ_REMOVE(head, elm, type, field) do { \
288  if (STAILQ_FIRST((head)) == (elm)) { \
289  STAILQ_REMOVE_HEAD((head), field); \
290  } \
291  else { \
292  struct type *curelm = STAILQ_FIRST((head)); \
293  while (STAILQ_NEXT(curelm, field) != (elm)) \
294  curelm = STAILQ_NEXT(curelm, field); \
295  STAILQ_REMOVE_AFTER(head, curelm, field); \
296  } \
297  TRASHIT((elm)->field.stqe_next); \
298 } while (0)
299 
300 #define STAILQ_REMOVE_HEAD(head, field) do { \
301  if ((STAILQ_FIRST((head)) = \
302  STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL) \
303  (head)->stqh_last = &STAILQ_FIRST((head)); \
304 } while (0)
305 
306 #define STAILQ_REMOVE_AFTER(head, elm, field) do { \
307  if ((STAILQ_NEXT(elm, field) = \
308  STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL) \
309  (head)->stqh_last = &STAILQ_NEXT((elm), field); \
310 } while (0)
311 
312 /*
313  * List declarations.
314  */
315 #define LIST_HEAD(name, type) \
316 struct name { \
317  struct type *lh_first; /* first element */ \
318 }
319 
320 #define LIST_HEAD_INITIALIZER(head) \
321  { NULL }
322 
323 #define LIST_ENTRY(type) \
324 struct { \
325  struct type *le_next; /* next element */ \
326  struct type **le_prev; /* address of previous next element */ \
327 }
328 
329 /*
330  * List functions.
331  */
332 
333 #if (defined(_KERNEL) && defined(INVARIANTS))
334 #define QMD_LIST_CHECK_HEAD(head, field) do { \
335  if (LIST_FIRST((head)) != NULL && \
336  LIST_FIRST((head))->field.le_prev != \
337  &LIST_FIRST((head))) \
338  panic("Bad list head %p first->prev != head", (head)); \
339 } while (0)
340 
341 #define QMD_LIST_CHECK_NEXT(elm, field) do { \
342  if (LIST_NEXT((elm), field) != NULL && \
343  LIST_NEXT((elm), field)->field.le_prev != \
344  &((elm)->field.le_next)) \
345  panic("Bad link elm %p next->prev != elm", (elm)); \
346 } while (0)
347 
348 #define QMD_LIST_CHECK_PREV(elm, field) do { \
349  if (*(elm)->field.le_prev != (elm)) \
350  panic("Bad link elm %p prev->next != elm", (elm)); \
351 } while (0)
352 #else
353 #define QMD_LIST_CHECK_HEAD(head, field)
354 #define QMD_LIST_CHECK_NEXT(elm, field)
355 #define QMD_LIST_CHECK_PREV(elm, field)
356 #endif /* (_KERNEL && INVARIANTS) */
357 
358 #define LIST_EMPTY(head) ((head)->lh_first == NULL)
359 
360 #define LIST_FIRST(head) ((head)->lh_first)
361 
362 #define LIST_FOREACH(var, head, field) \
363  for ((var) = LIST_FIRST((head)); \
364  (var); \
365  (var) = LIST_NEXT((var), field))
366 
367 #define LIST_FOREACH_SAFE(var, head, field, tvar) \
368  for ((var) = LIST_FIRST((head)); \
369  (var) && ((tvar) = LIST_NEXT((var), field), 1); \
370  (var) = (tvar))
371 
372 #define LIST_INIT(head) do { \
373  LIST_FIRST((head)) = NULL; \
374 } while (0)
375 
376 #define LIST_INSERT_AFTER(listelm, elm, field) do { \
377  QMD_LIST_CHECK_NEXT(listelm, field); \
378  if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
379  LIST_NEXT((listelm), field)->field.le_prev = \
380  &LIST_NEXT((elm), field); \
381  LIST_NEXT((listelm), field) = (elm); \
382  (elm)->field.le_prev = &LIST_NEXT((listelm), field); \
383 } while (0)
384 
385 #define LIST_INSERT_BEFORE(listelm, elm, field) do { \
386  QMD_LIST_CHECK_PREV(listelm, field); \
387  (elm)->field.le_prev = (listelm)->field.le_prev; \
388  LIST_NEXT((elm), field) = (listelm); \
389  *(listelm)->field.le_prev = (elm); \
390  (listelm)->field.le_prev = &LIST_NEXT((elm), field); \
391 } while (0)
392 
393 #define LIST_INSERT_HEAD(head, elm, field) do { \
394  QMD_LIST_CHECK_HEAD((head), field); \
395  if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL) \
396  LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
397  LIST_FIRST((head)) = (elm); \
398  (elm)->field.le_prev = &LIST_FIRST((head)); \
399 } while (0)
400 
401 #define LIST_NEXT(elm, field) ((elm)->field.le_next)
402 
403 #define LIST_REMOVE(elm, field) do { \
404  QMD_LIST_CHECK_NEXT(elm, field); \
405  QMD_LIST_CHECK_PREV(elm, field); \
406  if (LIST_NEXT((elm), field) != NULL) \
407  LIST_NEXT((elm), field)->field.le_prev = \
408  (elm)->field.le_prev; \
409  *(elm)->field.le_prev = LIST_NEXT((elm), field); \
410  TRASHIT((elm)->field.le_next); \
411  TRASHIT((elm)->field.le_prev); \
412 } while (0)
413 
414 /*
415  * Tail queue declarations.
416  */
417 #define TAILQ_HEAD(name, type) \
418 struct name { \
419  struct type *tqh_first; /* first element */ \
420  struct type **tqh_last; /* addr of last next element */ \
421  TRACEBUF \
422 }
423 
424 #define TAILQ_HEAD_INITIALIZER(head) \
425  { NULL, &(head).tqh_first }
426 
427 #define TAILQ_ENTRY(type) \
428 struct { \
429  struct type *tqe_next; /* next element */ \
430  struct type **tqe_prev; /* address of previous next element */ \
431  TRACEBUF \
432 }
433 
434 /*
435  * Tail queue functions.
436  */
437 #if (defined(_KERNEL) && defined(INVARIANTS))
438 #define QMD_TAILQ_CHECK_HEAD(head, field) do { \
439  if (!TAILQ_EMPTY(head) && \
440  TAILQ_FIRST((head))->field.tqe_prev != \
441  &TAILQ_FIRST((head))) \
442  panic("Bad tailq head %p first->prev != head", (head)); \
443 } while (0)
444 
445 #define QMD_TAILQ_CHECK_TAIL(head, field) do { \
446  if (*(head)->tqh_last != NULL) \
447  panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head)); \
448 } while (0)
449 
450 #define QMD_TAILQ_CHECK_NEXT(elm, field) do { \
451  if (TAILQ_NEXT((elm), field) != NULL && \
452  TAILQ_NEXT((elm), field)->field.tqe_prev != \
453  &((elm)->field.tqe_next)) \
454  panic("Bad link elm %p next->prev != elm", (elm)); \
455 } while (0)
456 
457 #define QMD_TAILQ_CHECK_PREV(elm, field) do { \
458  if (*(elm)->field.tqe_prev != (elm)) \
459  panic("Bad link elm %p prev->next != elm", (elm)); \
460 } while (0)
461 #else
462 #define QMD_TAILQ_CHECK_HEAD(head, field)
463 #define QMD_TAILQ_CHECK_TAIL(head, headname)
464 #define QMD_TAILQ_CHECK_NEXT(elm, field)
465 #define QMD_TAILQ_CHECK_PREV(elm, field)
466 #endif /* (_KERNEL && INVARIANTS) */
467 
468 #define TAILQ_CONCAT(head1, head2, field) do { \
469  if (!TAILQ_EMPTY(head2)) { \
470  *(head1)->tqh_last = (head2)->tqh_first; \
471  (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
472  (head1)->tqh_last = (head2)->tqh_last; \
473  TAILQ_INIT((head2)); \
474  QMD_TRACE_HEAD(head1); \
475  QMD_TRACE_HEAD(head2); \
476  } \
477 } while (0)
478 
479 #define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)
480 
481 #define TAILQ_FIRST(head) ((head)->tqh_first)
482 
483 #define TAILQ_FOREACH(var, head, field) \
484  for ((var) = TAILQ_FIRST((head)); \
485  (var); \
486  (var) = TAILQ_NEXT((var), field))
487 
488 #define TAILQ_FOREACH_SAFE(var, head, field, tvar) \
489  for ((var) = TAILQ_FIRST((head)); \
490  (var) && ((tvar) = TAILQ_NEXT((var), field), 1); \
491  (var) = (tvar))
492 
493 #define TAILQ_FOREACH_REVERSE(var, head, headname, field) \
494  for ((var) = TAILQ_LAST((head), headname); \
495  (var); \
496  (var) = TAILQ_PREV((var), headname, field))
497 
498 #define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar) \
499  for ((var) = TAILQ_LAST((head), headname); \
500  (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1); \
501  (var) = (tvar))
502 
503 #define TAILQ_INIT(head) do { \
504  TAILQ_FIRST((head)) = NULL; \
505  (head)->tqh_last = &TAILQ_FIRST((head)); \
506  QMD_TRACE_HEAD(head); \
507 } while (0)
508 
509 #define TAILQ_INSERT_AFTER(head, listelm, elm, field) do { \
510  QMD_TAILQ_CHECK_NEXT(listelm, field); \
511  if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
512  TAILQ_NEXT((elm), field)->field.tqe_prev = \
513  &TAILQ_NEXT((elm), field); \
514  else { \
515  (head)->tqh_last = &TAILQ_NEXT((elm), field); \
516  QMD_TRACE_HEAD(head); \
517  } \
518  TAILQ_NEXT((listelm), field) = (elm); \
519  (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field); \
520  QMD_TRACE_ELEM(&(elm)->field); \
521  QMD_TRACE_ELEM(&listelm->field); \
522 } while (0)
523 
524 #define TAILQ_INSERT_BEFORE(listelm, elm, field) do { \
525  QMD_TAILQ_CHECK_PREV(listelm, field); \
526  (elm)->field.tqe_prev = (listelm)->field.tqe_prev; \
527  TAILQ_NEXT((elm), field) = (listelm); \
528  *(listelm)->field.tqe_prev = (elm); \
529  (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \
530  QMD_TRACE_ELEM(&(elm)->field); \
531  QMD_TRACE_ELEM(&listelm->field); \
532 } while (0)
533 
534 #define TAILQ_INSERT_HEAD(head, elm, field) do { \
535  QMD_TAILQ_CHECK_HEAD(head, field); \
536  if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL) \
537  TAILQ_FIRST((head))->field.tqe_prev = \
538  &TAILQ_NEXT((elm), field); \
539  else \
540  (head)->tqh_last = &TAILQ_NEXT((elm), field); \
541  TAILQ_FIRST((head)) = (elm); \
542  (elm)->field.tqe_prev = &TAILQ_FIRST((head)); \
543  QMD_TRACE_HEAD(head); \
544  QMD_TRACE_ELEM(&(elm)->field); \
545 } while (0)
546 
547 #define TAILQ_INSERT_TAIL(head, elm, field) do { \
548  QMD_TAILQ_CHECK_TAIL(head, field); \
549  TAILQ_NEXT((elm), field) = NULL; \
550  (elm)->field.tqe_prev = (head)->tqh_last; \
551  *(head)->tqh_last = (elm); \
552  (head)->tqh_last = &TAILQ_NEXT((elm), field); \
553  QMD_TRACE_HEAD(head); \
554  QMD_TRACE_ELEM(&(elm)->field); \
555 } while (0)
556 
557 #define TAILQ_LAST(head, headname) \
558  (*(((struct headname *)((head)->tqh_last))->tqh_last))
559 
560 #define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
561 
562 #define TAILQ_PREV(elm, headname, field) \
563  (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
564 
565 #define TAILQ_REMOVE(head, elm, field) do { \
566  QMD_TAILQ_CHECK_NEXT(elm, field); \
567  QMD_TAILQ_CHECK_PREV(elm, field); \
568  if ((TAILQ_NEXT((elm), field)) != NULL) \
569  TAILQ_NEXT((elm), field)->field.tqe_prev = \
570  (elm)->field.tqe_prev; \
571  else { \
572  (head)->tqh_last = (elm)->field.tqe_prev; \
573  QMD_TRACE_HEAD(head); \
574  } \
575  *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field); \
576  TRASHIT((elm)->field.tqe_next); \
577  TRASHIT((elm)->field.tqe_prev); \
578  QMD_TRACE_ELEM(&(elm)->field); \
579 } while (0)
580 
581 
582 #ifdef _KERNEL
583 
584 /*
585  * XXX insque() and remque() are an old way of handling certain queues.
586  * They bogusly assumes that all queue heads look alike.
587  */
588 
589 struct quehead {
590  struct quehead *qh_link;
591  struct quehead *qh_rlink;
592 };
593 
594 #ifdef __CC_SUPPORTS___INLINE
595 
596 static __inline void
597 insque(void *a, void *b)
598 {
599  struct quehead *element = (struct quehead *)a,
600  *head = (struct quehead *)b;
601 
602  element->qh_link = head->qh_link;
603  element->qh_rlink = head;
604  head->qh_link = element;
605  element->qh_link->qh_rlink = element;
606 }
607 
608 static __inline void
609 remque(void *a)
610 {
611  struct quehead *element = (struct quehead *)a;
612 
613  element->qh_link->qh_rlink = element->qh_rlink;
614  element->qh_rlink->qh_link = element->qh_link;
615  element->qh_rlink = 0;
616 }
617 
618 #else /* !__CC_SUPPORTS___INLINE */
619 
620 void insque(void *a, void *b);
621 void remque(void *a);
622 
623 #endif /* __CC_SUPPORTS___INLINE */
624 
625 #endif /* _KERNEL */
626 
627 #endif /* !_SYS_QUEUE_H_ */