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1 /*-
2  * Copyright (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  */
30 
31 #ifndef _USER_QUEUE_H_
32 #define	_USER_QUEUE_H_
33 
34 #if !defined (__Userspace_os_Windows)
35 #include <sys/cdefs.h>
36 #endif
37 /*
38  * This file defines four types of data structures: singly-linked lists,
39  * singly-linked tail queues, lists and tail queues.
40  *
41  * A singly-linked list is headed by a single forward pointer. The elements
42  * are singly linked for minimum space and pointer manipulation overhead at
43  * the expense of O(n) removal for arbitrary elements. New elements can be
44  * added to the list after an existing element or at the head of the list.
45  * Elements being removed from the head of the list should use the explicit
46  * macro for this purpose for optimum efficiency. A singly-linked list may
47  * only be traversed in the forward direction.  Singly-linked lists are ideal
48  * for applications with large datasets and few or no removals or for
49  * implementing a LIFO queue.
50  *
51  * A singly-linked tail queue is headed by a pair of pointers, one to the
52  * head of the list and the other to the tail of the list. The elements are
53  * singly linked for minimum space and pointer manipulation overhead at the
54  * expense of O(n) removal for arbitrary elements. New elements can be added
55  * to the list after an existing element, at the head of the list, or at the
56  * end of the list. Elements being removed from the head of the tail queue
57  * should use the explicit macro for this purpose for optimum efficiency.
58  * A singly-linked tail queue may only be traversed in the forward direction.
59  * Singly-linked tail queues are ideal for applications with large datasets
60  * and few or no removals or for implementing a FIFO queue.
61  *
62  * A list is headed by a single forward pointer (or an array of forward
63  * pointers for a hash table header). The elements are doubly linked
64  * so that an arbitrary element can be removed without a need to
65  * traverse the list. New elements can be added to the list before
66  * or after an existing element or at the head of the list. A list
67  * may only be traversed in the forward direction.
68  *
69  * A tail queue is headed by a pair of pointers, one to the head of the
70  * list and the other to the tail of the list. The elements are doubly
71  * linked so that an arbitrary element can be removed without a need to
72  * traverse the list. New elements can be added to the list before or
73  * after an existing element, at the head of the list, or at the end of
74  * the list. A tail queue may be traversed in either direction.
75  *
76  * For details on the use of these macros, see the queue(3) manual page.
77  *
78  *
79  *				SLIST	LIST	STAILQ	TAILQ
80  * _HEAD			+	+	+	+
81  * _HEAD_INITIALIZER		+	+	+	+
82  * _ENTRY			+	+	+	+
83  * _INIT			+	+	+	+
84  * _EMPTY			+	+	+	+
85  * _FIRST			+	+	+	+
86  * _NEXT			+	+	+	+
87  * _PREV			-	-	-	+
88  * _LAST			-	-	+	+
89  * _FOREACH			+	+	+	+
90  * _FOREACH_SAFE		+	+	+	+
91  * _FOREACH_REVERSE		-	-	-	+
92  * _FOREACH_REVERSE_SAFE	-	-	-	+
93  * _INSERT_HEAD			+	+	+	+
94  * _INSERT_BEFORE		-	+	-	+
95  * _INSERT_AFTER		+	+	+	+
96  * _INSERT_TAIL			-	-	+	+
97  * _CONCAT			-	-	+	+
98  * _REMOVE_AFTER		+	-	+	-
99  * _REMOVE_HEAD			+	-	+	-
100  * _REMOVE			+	+	+	+
101  * _SWAP			+	+	+	+
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 #define	QMD_SAVELINK(name, link)	void **name = (void *)&(link)
116 
117 #define	QMD_TRACE_HEAD(head) do {					\
118 	(head)->trace.prevline = (head)->trace.lastline;		\
119 	(head)->trace.prevfile = (head)->trace.lastfile;		\
120 	(head)->trace.lastline = __LINE__;				\
121 	(head)->trace.lastfile = __FILE__;				\
122 } while (0)
123 
124 #define	QMD_TRACE_ELEM(elem) do {					\
125 	(elem)->trace.prevline = (elem)->trace.lastline;		\
126 	(elem)->trace.prevfile = (elem)->trace.lastfile;		\
127 	(elem)->trace.lastline = __LINE__;				\
128 	(elem)->trace.lastfile = __FILE__;				\
129 } while (0)
130 
131 #else
132 #define	QMD_TRACE_ELEM(elem)
133 #define	QMD_TRACE_HEAD(head)
134 #define	QMD_SAVELINK(name, link)
135 #define	TRACEBUF
136 #define	TRASHIT(x)
137 #endif	/* QUEUE_MACRO_DEBUG */
138 
139 /*
140  * Singly-linked List declarations.
141  */
142 #define	SLIST_HEAD(name, type)						\
143 struct name {								\
144 	struct type *slh_first;	/* first element */			\
145 }
146 
147 #define	SLIST_HEAD_INITIALIZER(head)					\
148 	{ NULL }
149 
150 #if defined (__Userspace_os_Windows)
151 #if defined (SLIST_ENTRY)
152 #undef SLIST_ENTRY
153 #endif
154 #endif
155 
156 #define	SLIST_ENTRY(type)						\
157 struct {								\
158 	struct type *sle_next;	/* next element */			\
159 }
160 
161 /*
162  * Singly-linked List functions.
163  */
164 #define	SLIST_EMPTY(head)	((head)->slh_first == NULL)
165 
166 #define	SLIST_FIRST(head)	((head)->slh_first)
167 
168 #define	SLIST_FOREACH(var, head, field)					\
169 	for ((var) = SLIST_FIRST((head));				\
170 	    (var);							\
171 	    (var) = SLIST_NEXT((var), field))
172 
173 #define	SLIST_FOREACH_SAFE(var, head, field, tvar)			\
174 	for ((var) = SLIST_FIRST((head));				\
175 	    (var) && ((tvar) = SLIST_NEXT((var), field), 1);		\
176 	    (var) = (tvar))
177 
178 #define	SLIST_FOREACH_PREVPTR(var, varp, head, field)			\
179 	for ((varp) = &SLIST_FIRST((head));				\
180 	    ((var) = *(varp)) != NULL;					\
181 	    (varp) = &SLIST_NEXT((var), field))
182 
183 #define	SLIST_INIT(head) do {						\
184 	SLIST_FIRST((head)) = NULL;					\
185 } while (0)
186 
187 #define	SLIST_INSERT_AFTER(slistelm, elm, field) do {			\
188 	SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);	\
189 	SLIST_NEXT((slistelm), field) = (elm);				\
190 } while (0)
191 
192 #define	SLIST_INSERT_HEAD(head, elm, field) do {			\
193 	SLIST_NEXT((elm), field) = SLIST_FIRST((head));			\
194 	SLIST_FIRST((head)) = (elm);					\
195 } while (0)
196 
197 #define	SLIST_NEXT(elm, field)	((elm)->field.sle_next)
198 
199 #define	SLIST_REMOVE(head, elm, type, field) do {			\
200 	QMD_SAVELINK(oldnext, (elm)->field.sle_next);			\
201 	if (SLIST_FIRST((head)) == (elm)) {				\
202 		SLIST_REMOVE_HEAD((head), field);			\
203 	}								\
204 	else {								\
205 		struct type *curelm = SLIST_FIRST((head));		\
206 		while (SLIST_NEXT(curelm, field) != (elm))		\
207 			curelm = SLIST_NEXT(curelm, field);		\
208 		SLIST_REMOVE_AFTER(curelm, field);			\
209 	}								\
210 	TRASHIT(*oldnext);						\
211 } while (0)
212 
213 #define SLIST_REMOVE_AFTER(elm, field) do {				\
214 	SLIST_NEXT(elm, field) =					\
215 	    SLIST_NEXT(SLIST_NEXT(elm, field), field);			\
216 } while (0)
217 
218 #define	SLIST_REMOVE_HEAD(head, field) do {				\
219 	SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);	\
220 } while (0)
221 
222 #define SLIST_SWAP(head1, head2, type) do {				\
223 	struct type *swap_first = SLIST_FIRST(head1);			\
224 	SLIST_FIRST(head1) = SLIST_FIRST(head2);			\
225 	SLIST_FIRST(head2) = swap_first;				\
226 } while (0)
227 
228 /*
229  * Singly-linked Tail queue declarations.
230  */
231 #define	STAILQ_HEAD(name, type)						\
232 struct name {								\
233 	struct type *stqh_first;/* first element */			\
234 	struct type **stqh_last;/* addr of last next element */		\
235 }
236 
237 #define	STAILQ_HEAD_INITIALIZER(head)					\
238 	{ NULL, &(head).stqh_first }
239 
240 #define	STAILQ_ENTRY(type)						\
241 struct {								\
242 	struct type *stqe_next;	/* next element */			\
243 }
244 
245 /*
246  * Singly-linked Tail queue functions.
247  */
248 #define	STAILQ_CONCAT(head1, head2) do {				\
249 	if (!STAILQ_EMPTY((head2))) {					\
250 		*(head1)->stqh_last = (head2)->stqh_first;		\
251 		(head1)->stqh_last = (head2)->stqh_last;		\
252 		STAILQ_INIT((head2));					\
253 	}								\
254 } while (0)
255 
256 #define	STAILQ_EMPTY(head)	((head)->stqh_first == NULL)
257 
258 #define	STAILQ_FIRST(head)	((head)->stqh_first)
259 
260 #define	STAILQ_FOREACH(var, head, field)				\
261 	for((var) = STAILQ_FIRST((head));				\
262 	   (var);							\
263 	   (var) = STAILQ_NEXT((var), field))
264 
265 
266 #define	STAILQ_FOREACH_SAFE(var, head, field, tvar)			\
267 	for ((var) = STAILQ_FIRST((head));				\
268 	    (var) && ((tvar) = STAILQ_NEXT((var), field), 1);		\
269 	    (var) = (tvar))
270 
271 #define	STAILQ_INIT(head) do {						\
272 	STAILQ_FIRST((head)) = NULL;					\
273 	(head)->stqh_last = &STAILQ_FIRST((head));			\
274 } while (0)
275 
276 #define	STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {		\
277 	if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
278 		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
279 	STAILQ_NEXT((tqelm), field) = (elm);				\
280 } while (0)
281 
282 #define	STAILQ_INSERT_HEAD(head, elm, field) do {			\
283 	if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL)	\
284 		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
285 	STAILQ_FIRST((head)) = (elm);					\
286 } while (0)
287 
288 #define	STAILQ_INSERT_TAIL(head, elm, field) do {			\
289 	STAILQ_NEXT((elm), field) = NULL;				\
290 	*(head)->stqh_last = (elm);					\
291 	(head)->stqh_last = &STAILQ_NEXT((elm), field);			\
292 } while (0)
293 
294 #define	STAILQ_LAST(head, type, field)					\
295 	(STAILQ_EMPTY((head)) ?						\
296 		NULL :							\
297 	        ((struct type *)(void *)				\
298 		((char *)((head)->stqh_last) - __offsetof(struct type, field))))
299 
300 #define	STAILQ_NEXT(elm, field)	((elm)->field.stqe_next)
301 
302 #define	STAILQ_REMOVE(head, elm, type, field) do {			\
303 	QMD_SAVELINK(oldnext, (elm)->field.stqe_next);			\
304 	if (STAILQ_FIRST((head)) == (elm)) {				\
305 		STAILQ_REMOVE_HEAD((head), field);			\
306 	}								\
307 	else {								\
308 		struct type *curelm = STAILQ_FIRST((head));		\
309 		while (STAILQ_NEXT(curelm, field) != (elm))		\
310 			curelm = STAILQ_NEXT(curelm, field);		\
311 		STAILQ_REMOVE_AFTER(head, curelm, field);		\
312 	}								\
313 	TRASHIT(*oldnext);						\
314 } while (0)
315 
316 #define STAILQ_REMOVE_AFTER(head, elm, field) do {			\
317 	if ((STAILQ_NEXT(elm, field) =					\
318 	     STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)	\
319 		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
320 } while (0)
321 
322 #define	STAILQ_REMOVE_HEAD(head, field) do {				\
323 	if ((STAILQ_FIRST((head)) =					\
324 	     STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)		\
325 		(head)->stqh_last = &STAILQ_FIRST((head));		\
326 } while (0)
327 
328 #define STAILQ_SWAP(head1, head2, type) do {				\
329 	struct type *swap_first = STAILQ_FIRST(head1);			\
330 	struct type **swap_last = (head1)->stqh_last;			\
331 	STAILQ_FIRST(head1) = STAILQ_FIRST(head2);			\
332 	(head1)->stqh_last = (head2)->stqh_last;			\
333 	STAILQ_FIRST(head2) = swap_first;				\
334 	(head2)->stqh_last = swap_last;					\
335 	if (STAILQ_EMPTY(head1))					\
336 		(head1)->stqh_last = &STAILQ_FIRST(head1);		\
337 	if (STAILQ_EMPTY(head2))					\
338 		(head2)->stqh_last = &STAILQ_FIRST(head2);		\
339 } while (0)
340 
341 
342 /*
343  * List declarations.
344  */
345 #define	LIST_HEAD(name, type)						\
346 struct name {								\
347 	struct type *lh_first;	/* first element */			\
348 }
349 
350 #define	LIST_HEAD_INITIALIZER(head)					\
351 	{ NULL }
352 
353 #define	LIST_ENTRY(type)						\
354 struct {								\
355 	struct type *le_next;	/* next element */			\
356 	struct type **le_prev;	/* address of previous next element */	\
357 }
358 
359 /*
360  * List functions.
361  */
362 
363 #if defined(INVARIANTS)
364 #define	QMD_LIST_CHECK_HEAD(head, field) do {					\
365 	if (LIST_FIRST((head)) != NULL &&					\
366 	    LIST_FIRST((head))->field.le_prev !=				\
367 	     &LIST_FIRST((head)))						\
368 		panic("Bad list head %p first->prev != head", (void *)(head));	\
369 } while (0)
370 
371 #define	QMD_LIST_CHECK_NEXT(elm, field) do {					\
372 	if (LIST_NEXT((elm), field) != NULL &&					\
373 	    LIST_NEXT((elm), field)->field.le_prev !=				\
374 	     &((elm)->field.le_next))						\
375 	     	panic("Bad link elm %p next->prev != elm", (void *)(elm));	\
376 } while (0)
377 
378 #define	QMD_LIST_CHECK_PREV(elm, field) do {					\
379 	if (*(elm)->field.le_prev != (elm))					\
380 		panic("Bad link elm %p prev->next != elm", (void *)(elm));	\
381 } while (0)
382 #else
383 #define	QMD_LIST_CHECK_HEAD(head, field)
384 #define	QMD_LIST_CHECK_NEXT(elm, field)
385 #define	QMD_LIST_CHECK_PREV(elm, field)
386 #endif /* (INVARIANTS) */
387 
388 #define	LIST_EMPTY(head)	((head)->lh_first == NULL)
389 
390 #define	LIST_FIRST(head)	((head)->lh_first)
391 
392 #define	LIST_FOREACH(var, head, field)					\
393 	for ((var) = LIST_FIRST((head));				\
394 	    (var);							\
395 	    (var) = LIST_NEXT((var), field))
396 
397 #define	LIST_FOREACH_SAFE(var, head, field, tvar)			\
398 	for ((var) = LIST_FIRST((head));				\
399 	    (var) && ((tvar) = LIST_NEXT((var), field), 1);		\
400 	    (var) = (tvar))
401 
402 #define	LIST_INIT(head) do {						\
403 	LIST_FIRST((head)) = NULL;					\
404 } while (0)
405 
406 #define	LIST_INSERT_AFTER(listelm, elm, field) do {			\
407 	QMD_LIST_CHECK_NEXT(listelm, field);				\
408 	if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
409 		LIST_NEXT((listelm), field)->field.le_prev =		\
410 		    &LIST_NEXT((elm), field);				\
411 	LIST_NEXT((listelm), field) = (elm);				\
412 	(elm)->field.le_prev = &LIST_NEXT((listelm), field);		\
413 } while (0)
414 
415 #define	LIST_INSERT_BEFORE(listelm, elm, field) do {			\
416 	QMD_LIST_CHECK_PREV(listelm, field);				\
417 	(elm)->field.le_prev = (listelm)->field.le_prev;		\
418 	LIST_NEXT((elm), field) = (listelm);				\
419 	*(listelm)->field.le_prev = (elm);				\
420 	(listelm)->field.le_prev = &LIST_NEXT((elm), field);		\
421 } while (0)
422 
423 #define	LIST_INSERT_HEAD(head, elm, field) do {				\
424 	QMD_LIST_CHECK_HEAD((head), field);				\
425 	if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)	\
426 		LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
427 	LIST_FIRST((head)) = (elm);					\
428 	(elm)->field.le_prev = &LIST_FIRST((head));			\
429 } while (0)
430 
431 #define	LIST_NEXT(elm, field)	((elm)->field.le_next)
432 
433 #define	LIST_REMOVE(elm, field) do {					\
434 	QMD_SAVELINK(oldnext, (elm)->field.le_next);			\
435 	QMD_SAVELINK(oldprev, (elm)->field.le_prev);			\
436 	QMD_LIST_CHECK_NEXT(elm, field);				\
437 	QMD_LIST_CHECK_PREV(elm, field);				\
438 	if (LIST_NEXT((elm), field) != NULL)				\
439 		LIST_NEXT((elm), field)->field.le_prev = 		\
440 		    (elm)->field.le_prev;				\
441 	*(elm)->field.le_prev = LIST_NEXT((elm), field);		\
442 	TRASHIT(*oldnext);						\
443 	TRASHIT(*oldprev);						\
444 } while (0)
445 
446 #define LIST_SWAP(head1, head2, type, field) do {			\
447 	struct type *swap_tmp = LIST_FIRST((head1));			\
448 	LIST_FIRST((head1)) = LIST_FIRST((head2));			\
449 	LIST_FIRST((head2)) = swap_tmp;					\
450 	if ((swap_tmp = LIST_FIRST((head1))) != NULL)			\
451 		swap_tmp->field.le_prev = &LIST_FIRST((head1));		\
452 	if ((swap_tmp = LIST_FIRST((head2))) != NULL)			\
453 		swap_tmp->field.le_prev = &LIST_FIRST((head2));		\
454 } while (0)
455 
456 /*
457  * Tail queue declarations.
458  */
459 #define	TAILQ_HEAD(name, type)						\
460 struct name {								\
461 	struct type *tqh_first;	/* first element */			\
462 	struct type **tqh_last;	/* addr of last next element */		\
463 	TRACEBUF							\
464 }
465 
466 #define	TAILQ_HEAD_INITIALIZER(head)					\
467 	{ NULL, &(head).tqh_first }
468 
469 #define	TAILQ_ENTRY(type)						\
470 struct {								\
471 	struct type *tqe_next;	/* next element */			\
472 	struct type **tqe_prev;	/* address of previous next element */	\
473 	TRACEBUF							\
474 }
475 
476 /*
477  * Tail queue functions.
478  */
479 #if defined(INVARIANTS)
480 #define	QMD_TAILQ_CHECK_HEAD(head, field) do {					\
481 	if (!TAILQ_EMPTY(head) &&						\
482 	    TAILQ_FIRST((head))->field.tqe_prev !=				\
483 	     &TAILQ_FIRST((head)))						\
484 		panic("Bad tailq head %p first->prev != head", (void *)(head));	\
485 } while (0)
486 
487 #define	QMD_TAILQ_CHECK_TAIL(head, field) do {					\
488 	if (*(head)->tqh_last != NULL)						\
489 	    	panic("Bad tailq NEXT(%p->tqh_last) != NULL", (void *)(head)); 	\
490 } while (0)
491 
492 #define	QMD_TAILQ_CHECK_NEXT(elm, field) do {					\
493 	if (TAILQ_NEXT((elm), field) != NULL &&					\
494 	    TAILQ_NEXT((elm), field)->field.tqe_prev !=				\
495 	     &((elm)->field.tqe_next))						\
496 		panic("Bad link elm %p next->prev != elm", (void *)(elm));	\
497 } while (0)
498 
499 #define	QMD_TAILQ_CHECK_PREV(elm, field) do {					\
500 	if (*(elm)->field.tqe_prev != (elm))					\
501 		panic("Bad link elm %p prev->next != elm", (void *)(elm));	\
502 } while (0)
503 #else
504 #define	QMD_TAILQ_CHECK_HEAD(head, field)
505 #define	QMD_TAILQ_CHECK_TAIL(head, headname)
506 #define	QMD_TAILQ_CHECK_NEXT(elm, field)
507 #define	QMD_TAILQ_CHECK_PREV(elm, field)
508 #endif /* (INVARIANTS) */
509 
510 #define	TAILQ_CONCAT(head1, head2, field) do {				\
511 	if (!TAILQ_EMPTY(head2)) {					\
512 		*(head1)->tqh_last = (head2)->tqh_first;		\
513 		(head2)->tqh_first->field.tqe_prev = (head1)->tqh_last;	\
514 		(head1)->tqh_last = (head2)->tqh_last;			\
515 		TAILQ_INIT((head2));					\
516 		QMD_TRACE_HEAD(head1);					\
517 		QMD_TRACE_HEAD(head2);					\
518 	}								\
519 } while (0)
520 
521 #define	TAILQ_EMPTY(head)	((head)->tqh_first == NULL)
522 
523 #define	TAILQ_FIRST(head)	((head)->tqh_first)
524 
525 #define	TAILQ_FOREACH(var, head, field)					\
526 	for ((var) = TAILQ_FIRST((head));				\
527 	    (var);							\
528 	    (var) = TAILQ_NEXT((var), field))
529 
530 #define	TAILQ_FOREACH_SAFE(var, head, field, tvar)			\
531 	for ((var) = TAILQ_FIRST((head));				\
532 	    (var) && ((tvar) = TAILQ_NEXT((var), field), 1);		\
533 	    (var) = (tvar))
534 
535 #define	TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
536 	for ((var) = TAILQ_LAST((head), headname);			\
537 	    (var);							\
538 	    (var) = TAILQ_PREV((var), headname, field))
539 
540 #define	TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)	\
541 	for ((var) = TAILQ_LAST((head), headname);			\
542 	    (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);	\
543 	    (var) = (tvar))
544 
545 #define	TAILQ_INIT(head) do {						\
546 	TAILQ_FIRST((head)) = NULL;					\
547 	(head)->tqh_last = &TAILQ_FIRST((head));			\
548 	QMD_TRACE_HEAD(head);						\
549 } while (0)
550 
551 #define	TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
552 	QMD_TAILQ_CHECK_NEXT(listelm, field);				\
553 	if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
554 		TAILQ_NEXT((elm), field)->field.tqe_prev = 		\
555 		    &TAILQ_NEXT((elm), field);				\
556 	else {								\
557 		(head)->tqh_last = &TAILQ_NEXT((elm), field);		\
558 		QMD_TRACE_HEAD(head);					\
559 	}								\
560 	TAILQ_NEXT((listelm), field) = (elm);				\
561 	(elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);		\
562 	QMD_TRACE_ELEM(&(elm)->field);					\
563 	QMD_TRACE_ELEM(&listelm->field);				\
564 } while (0)
565 
566 #define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
567 	QMD_TAILQ_CHECK_PREV(listelm, field);				\
568 	(elm)->field.tqe_prev = (listelm)->field.tqe_prev;		\
569 	TAILQ_NEXT((elm), field) = (listelm);				\
570 	*(listelm)->field.tqe_prev = (elm);				\
571 	(listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);		\
572 	QMD_TRACE_ELEM(&(elm)->field);					\
573 	QMD_TRACE_ELEM(&listelm->field);				\
574 } while (0)
575 
576 #define	TAILQ_INSERT_HEAD(head, elm, field) do {			\
577 	QMD_TAILQ_CHECK_HEAD(head, field);				\
578 	if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)	\
579 		TAILQ_FIRST((head))->field.tqe_prev =			\
580 		    &TAILQ_NEXT((elm), field);				\
581 	else								\
582 		(head)->tqh_last = &TAILQ_NEXT((elm), field);		\
583 	TAILQ_FIRST((head)) = (elm);					\
584 	(elm)->field.tqe_prev = &TAILQ_FIRST((head));			\
585 	QMD_TRACE_HEAD(head);						\
586 	QMD_TRACE_ELEM(&(elm)->field);					\
587 } while (0)
588 
589 #define	TAILQ_INSERT_TAIL(head, elm, field) do {			\
590 	QMD_TAILQ_CHECK_TAIL(head, field);				\
591 	TAILQ_NEXT((elm), field) = NULL;				\
592 	(elm)->field.tqe_prev = (head)->tqh_last;			\
593 	*(head)->tqh_last = (elm);					\
594 	(head)->tqh_last = &TAILQ_NEXT((elm), field);			\
595 	QMD_TRACE_HEAD(head);						\
596 	QMD_TRACE_ELEM(&(elm)->field);					\
597 } while (0)
598 
599 #define	TAILQ_LAST(head, headname)					\
600 	(*(((struct headname *)((head)->tqh_last))->tqh_last))
601 
602 #define	TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
603 
604 #define	TAILQ_PREV(elm, headname, field)				\
605 	(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
606 
607 #define	TAILQ_REMOVE(head, elm, field) do {				\
608 	QMD_SAVELINK(oldnext, (elm)->field.tqe_next);			\
609 	QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);			\
610 	QMD_TAILQ_CHECK_NEXT(elm, field);				\
611 	QMD_TAILQ_CHECK_PREV(elm, field);				\
612 	if ((TAILQ_NEXT((elm), field)) != NULL)				\
613 		TAILQ_NEXT((elm), field)->field.tqe_prev = 		\
614 		    (elm)->field.tqe_prev;				\
615 	else {								\
616 		(head)->tqh_last = (elm)->field.tqe_prev;		\
617 		QMD_TRACE_HEAD(head);					\
618 	}								\
619 	*(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);		\
620 	TRASHIT(*oldnext);						\
621 	TRASHIT(*oldprev);						\
622 	QMD_TRACE_ELEM(&(elm)->field);					\
623 } while (0)
624 
625 #define TAILQ_SWAP(head1, head2, type, field) do {			\
626 	struct type *swap_first = (head1)->tqh_first;			\
627 	struct type **swap_last = (head1)->tqh_last;			\
628 	(head1)->tqh_first = (head2)->tqh_first;			\
629 	(head1)->tqh_last = (head2)->tqh_last;				\
630 	(head2)->tqh_first = swap_first;				\
631 	(head2)->tqh_last = swap_last;					\
632 	if ((swap_first = (head1)->tqh_first) != NULL)			\
633 		swap_first->field.tqe_prev = &(head1)->tqh_first;	\
634 	else								\
635 		(head1)->tqh_last = &(head1)->tqh_first;		\
636 	if ((swap_first = (head2)->tqh_first) != NULL)			\
637 		swap_first->field.tqe_prev = &(head2)->tqh_first;	\
638 	else								\
639 		(head2)->tqh_last = &(head2)->tqh_first;		\
640 } while (0)
641 
642 #endif /* !_SYS_QUEUE_H_ */
643