summaryrefslogblamecommitdiff
path: root/system/bsd-compat-headers/sys-queue.h
blob: a38499a2673d7156c104f40370b2f5fd9c9667d5 (plain) (tree)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846












































































































































































































































































































































































































































































































































































































































































































































































































































































                                                                                 
/*	$NetBSD: queue.h,v 1.70 2015/11/02 15:21:23 christos Exp $	*/

/*
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)queue.h	8.5 (Berkeley) 8/20/94
 */

#ifndef	_SYS_QUEUE_H_
#define	_SYS_QUEUE_H_

/*
 * This file defines five types of data structures: singly-linked lists,
 * lists, simple queues, tail queues, and circular queues.
 *
 * A singly-linked list is headed by a single forward pointer. The
 * elements are singly linked for minimum space and pointer manipulation
 * overhead at the expense of O(n) removal for arbitrary elements. New
 * elements can be added to the list after an existing element or at the
 * head of the list.  Elements being removed from the head of the list
 * should use the explicit macro for this purpose for optimum
 * efficiency. A singly-linked list may only be traversed in the forward
 * direction.  Singly-linked lists are ideal for applications with large
 * datasets and few or no removals or for implementing a LIFO queue.
 *
 * A list is headed by a single forward pointer (or an array of forward
 * pointers for a hash table header). The elements are doubly linked
 * so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before
 * or after an existing element or at the head of the list. A list
 * may only be traversed in the forward direction.
 *
 * A simple queue is headed by a pair of pointers, one the head of the
 * list and the other to the tail of the list. The elements are singly
 * linked to save space, so elements can only be removed from the
 * head of the list. New elements can be added to the list after
 * an existing element, at the head of the list, or at the end of the
 * list. A simple queue may only be traversed in the forward direction.
 *
 * A tail queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or
 * after an existing element, at the head of the list, or at the end of
 * the list. A tail queue may be traversed in either direction.
 *
 * A circle queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or after
 * an existing element, at the head of the list, or at the end of the list.
 * A circle queue may be traversed in either direction, but has a more
 * complex end of list detection.
 *
 * For details on the use of these macros, see the queue(3) manual page.
 */

/*
 * Include the definition of NULL only on NetBSD because sys/null.h
 * is not available elsewhere.  This conditional makes the header
 * portable and it can simply be dropped verbatim into any system.
 * The caveat is that on other systems some other header
 * must provide NULL before the macros can be used.
 */
#ifdef __NetBSD__
#include <sys/null.h>
#endif

#if defined(QUEUEDEBUG)
# if defined(_KERNEL)
#  define QUEUEDEBUG_ABORT(...) panic(__VA_ARGS__)
# else
#  include <err.h>
#  define QUEUEDEBUG_ABORT(...) err(1, __VA_ARGS__)
# endif
#endif

/*
 * Singly-linked List definitions.
 */
#define	SLIST_HEAD(name, type)						\
struct name {								\
	struct type *slh_first;	/* first element */			\
}

#define	SLIST_HEAD_INITIALIZER(head)					\
	{ NULL }

#define	SLIST_ENTRY(type)						\
struct {								\
	struct type *sle_next;	/* next element */			\
}

/*
 * Singly-linked List access methods.
 */
#define	SLIST_FIRST(head)	((head)->slh_first)
#define	SLIST_END(head)		NULL
#define	SLIST_EMPTY(head)	((head)->slh_first == NULL)
#define	SLIST_NEXT(elm, field)	((elm)->field.sle_next)

#define	SLIST_FOREACH(var, head, field)					\
	for((var) = (head)->slh_first;					\
	    (var) != SLIST_END(head);					\
	    (var) = (var)->field.sle_next)

#define	SLIST_FOREACH_SAFE(var, head, field, tvar)			\
	for ((var) = SLIST_FIRST((head));				\
	    (var) != SLIST_END(head) &&					\
	    ((tvar) = SLIST_NEXT((var), field), 1);			\
	    (var) = (tvar))

/*
 * Singly-linked List functions.
 */
#define	SLIST_INIT(head) do {						\
	(head)->slh_first = SLIST_END(head);				\
} while (/*CONSTCOND*/0)

#define	SLIST_INSERT_AFTER(slistelm, elm, field) do {			\
	(elm)->field.sle_next = (slistelm)->field.sle_next;		\
	(slistelm)->field.sle_next = (elm);				\
} while (/*CONSTCOND*/0)

#define	SLIST_INSERT_HEAD(head, elm, field) do {			\
	(elm)->field.sle_next = (head)->slh_first;			\
	(head)->slh_first = (elm);					\
} while (/*CONSTCOND*/0)

#define	SLIST_REMOVE_AFTER(slistelm, field) do {			\
	(slistelm)->field.sle_next =					\
	    SLIST_NEXT(SLIST_NEXT((slistelm), field), field);		\
} while (/*CONSTCOND*/0)

#define	SLIST_REMOVE_HEAD(head, field) do {				\
	(head)->slh_first = (head)->slh_first->field.sle_next;		\
} while (/*CONSTCOND*/0)

#define	SLIST_REMOVE(head, elm, type, field) do {			\
	if ((head)->slh_first == (elm)) {				\
		SLIST_REMOVE_HEAD((head), field);			\
	}								\
	else {								\
		struct type *curelm = (head)->slh_first;		\
		while(curelm->field.sle_next != (elm))			\
			curelm = curelm->field.sle_next;		\
		curelm->field.sle_next =				\
		    curelm->field.sle_next->field.sle_next;		\
	}								\
} while (/*CONSTCOND*/0)


/*
 * List definitions.
 */
#define	LIST_HEAD(name, type)						\
struct name {								\
	struct type *lh_first;	/* first element */			\
}

#define	LIST_HEAD_INITIALIZER(head)					\
	{ NULL }

#define	LIST_ENTRY(type)						\
struct {								\
	struct type *le_next;	/* next element */			\
	struct type **le_prev;	/* address of previous next element */	\
}

/*
 * List access methods.
 */
#define	LIST_FIRST(head)		((head)->lh_first)
#define	LIST_END(head)			NULL
#define	LIST_EMPTY(head)		((head)->lh_first == LIST_END(head))
#define	LIST_NEXT(elm, field)		((elm)->field.le_next)

#define	LIST_FOREACH(var, head, field)					\
	for ((var) = ((head)->lh_first);				\
	    (var) != LIST_END(head);					\
	    (var) = ((var)->field.le_next))

#define	LIST_FOREACH_SAFE(var, head, field, tvar)			\
	for ((var) = LIST_FIRST((head));				\
	    (var) != LIST_END(head) &&					\
	    ((tvar) = LIST_NEXT((var), field), 1);			\
	    (var) = (tvar))

#define	LIST_MOVE(head1, head2) do {					\
	LIST_INIT((head2));						\
	if (!LIST_EMPTY((head1))) {					\
		(head2)->lh_first = (head1)->lh_first;			\
		LIST_INIT((head1));					\
	}								\
} while (/*CONSTCOND*/0)

/*
 * List functions.
 */
#if defined(QUEUEDEBUG)
#define	QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)			\
	if ((head)->lh_first &&						\
	    (head)->lh_first->field.le_prev != &(head)->lh_first)	\
		QUEUEDEBUG_ABORT("LIST_INSERT_HEAD %p %s:%d", (head),	\
		    __FILE__, __LINE__);
#define	QUEUEDEBUG_LIST_OP(elm, field)					\
	if ((elm)->field.le_next &&					\
	    (elm)->field.le_next->field.le_prev !=			\
	    &(elm)->field.le_next)					\
		QUEUEDEBUG_ABORT("LIST_* forw %p %s:%d", (elm),		\
		    __FILE__, __LINE__);				\
	if (*(elm)->field.le_prev != (elm))				\
		QUEUEDEBUG_ABORT("LIST_* back %p %s:%d", (elm),		\
		    __FILE__, __LINE__);
#define	QUEUEDEBUG_LIST_POSTREMOVE(elm, field)				\
	(elm)->field.le_next = (void *)1L;				\
	(elm)->field.le_prev = (void *)1L;
#else
#define	QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)
#define	QUEUEDEBUG_LIST_OP(elm, field)
#define	QUEUEDEBUG_LIST_POSTREMOVE(elm, field)
#endif

#define	LIST_INIT(head) do {						\
	(head)->lh_first = LIST_END(head);				\
} while (/*CONSTCOND*/0)

#define	LIST_INSERT_AFTER(listelm, elm, field) do {			\
	QUEUEDEBUG_LIST_OP((listelm), field)				\
	if (((elm)->field.le_next = (listelm)->field.le_next) != 	\
	    LIST_END(head))						\
		(listelm)->field.le_next->field.le_prev =		\
		    &(elm)->field.le_next;				\
	(listelm)->field.le_next = (elm);				\
	(elm)->field.le_prev = &(listelm)->field.le_next;		\
} while (/*CONSTCOND*/0)

#define	LIST_INSERT_BEFORE(listelm, elm, field) do {			\
	QUEUEDEBUG_LIST_OP((listelm), field)				\
	(elm)->field.le_prev = (listelm)->field.le_prev;		\
	(elm)->field.le_next = (listelm);				\
	*(listelm)->field.le_prev = (elm);				\
	(listelm)->field.le_prev = &(elm)->field.le_next;		\
} while (/*CONSTCOND*/0)

#define	LIST_INSERT_HEAD(head, elm, field) do {				\
	QUEUEDEBUG_LIST_INSERT_HEAD((head), (elm), field)		\
	if (((elm)->field.le_next = (head)->lh_first) != LIST_END(head))\
		(head)->lh_first->field.le_prev = &(elm)->field.le_next;\
	(head)->lh_first = (elm);					\
	(elm)->field.le_prev = &(head)->lh_first;			\
} while (/*CONSTCOND*/0)

#define	LIST_REMOVE(elm, field) do {					\
	QUEUEDEBUG_LIST_OP((elm), field)				\
	if ((elm)->field.le_next != NULL)				\
		(elm)->field.le_next->field.le_prev = 			\
		    (elm)->field.le_prev;				\
	*(elm)->field.le_prev = (elm)->field.le_next;			\
	QUEUEDEBUG_LIST_POSTREMOVE((elm), field)			\
} while (/*CONSTCOND*/0)

#define LIST_REPLACE(elm, elm2, field) do {				\
	if (((elm2)->field.le_next = (elm)->field.le_next) != NULL)	\
		(elm2)->field.le_next->field.le_prev =			\
		    &(elm2)->field.le_next;				\
	(elm2)->field.le_prev = (elm)->field.le_prev;			\
	*(elm2)->field.le_prev = (elm2);				\
	QUEUEDEBUG_LIST_POSTREMOVE((elm), field)			\
} while (/*CONSTCOND*/0)

/*
 * Simple queue definitions.
 */
#define	SIMPLEQ_HEAD(name, type)					\
struct name {								\
	struct type *sqh_first;	/* first element */			\
	struct type **sqh_last;	/* addr of last next element */		\
}

#define	SIMPLEQ_HEAD_INITIALIZER(head)					\
	{ NULL, &(head).sqh_first }

#define	SIMPLEQ_ENTRY(type)						\
struct {								\
	struct type *sqe_next;	/* next element */			\
}

/*
 * Simple queue access methods.
 */
#define	SIMPLEQ_FIRST(head)		((head)->sqh_first)
#define	SIMPLEQ_END(head)		NULL
#define	SIMPLEQ_EMPTY(head)		((head)->sqh_first == SIMPLEQ_END(head))
#define	SIMPLEQ_NEXT(elm, field)	((elm)->field.sqe_next)

#define	SIMPLEQ_FOREACH(var, head, field)				\
	for ((var) = ((head)->sqh_first);				\
	    (var) != SIMPLEQ_END(head);					\
	    (var) = ((var)->field.sqe_next))

#define	SIMPLEQ_FOREACH_SAFE(var, head, field, next)			\
	for ((var) = ((head)->sqh_first);				\
	    (var) != SIMPLEQ_END(head) &&				\
	    ((next = ((var)->field.sqe_next)), 1);			\
	    (var) = (next))

/*
 * Simple queue functions.
 */
#define	SIMPLEQ_INIT(head) do {						\
	(head)->sqh_first = NULL;					\
	(head)->sqh_last = &(head)->sqh_first;				\
} while (/*CONSTCOND*/0)

#define	SIMPLEQ_INSERT_HEAD(head, elm, field) do {			\
	if (((elm)->field.sqe_next = (head)->sqh_first) == NULL)	\
		(head)->sqh_last = &(elm)->field.sqe_next;		\
	(head)->sqh_first = (elm);					\
} while (/*CONSTCOND*/0)

#define	SIMPLEQ_INSERT_TAIL(head, elm, field) do {			\
	(elm)->field.sqe_next = NULL;					\
	*(head)->sqh_last = (elm);					\
	(head)->sqh_last = &(elm)->field.sqe_next;			\
} while (/*CONSTCOND*/0)

#define	SIMPLEQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	if (((elm)->field.sqe_next = (listelm)->field.sqe_next) == NULL)\
		(head)->sqh_last = &(elm)->field.sqe_next;		\
	(listelm)->field.sqe_next = (elm);				\
} while (/*CONSTCOND*/0)

#define	SIMPLEQ_REMOVE_HEAD(head, field) do {				\
	if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL) \
		(head)->sqh_last = &(head)->sqh_first;			\
} while (/*CONSTCOND*/0)

#define SIMPLEQ_REMOVE_AFTER(head, elm, field) do {			\
	if (((elm)->field.sqe_next = (elm)->field.sqe_next->field.sqe_next) \
	    == NULL)							\
		(head)->sqh_last = &(elm)->field.sqe_next;		\
} while (/*CONSTCOND*/0)

#define	SIMPLEQ_REMOVE(head, elm, type, field) do {			\
	if ((head)->sqh_first == (elm)) {				\
		SIMPLEQ_REMOVE_HEAD((head), field);			\
	} else {							\
		struct type *curelm = (head)->sqh_first;		\
		while (curelm->field.sqe_next != (elm))			\
			curelm = curelm->field.sqe_next;		\
		if ((curelm->field.sqe_next =				\
			curelm->field.sqe_next->field.sqe_next) == NULL) \
			    (head)->sqh_last = &(curelm)->field.sqe_next; \
	}								\
} while (/*CONSTCOND*/0)

#define	SIMPLEQ_CONCAT(head1, head2) do {				\
	if (!SIMPLEQ_EMPTY((head2))) {					\
		*(head1)->sqh_last = (head2)->sqh_first;		\
		(head1)->sqh_last = (head2)->sqh_last;		\
		SIMPLEQ_INIT((head2));					\
	}								\
} while (/*CONSTCOND*/0)

#define	SIMPLEQ_LAST(head, type, field)					\
	(SIMPLEQ_EMPTY((head)) ?						\
		NULL :							\
	        ((struct type *)(void *)				\
		((char *)((head)->sqh_last) - offsetof(struct type, field))))

/*
 * Tail queue definitions.
 */
#define	_TAILQ_HEAD(name, type, qual)					\
struct name {								\
	qual type *tqh_first;		/* first element */		\
	qual type *qual *tqh_last;	/* addr of last next element */	\
}
#define TAILQ_HEAD(name, type)	_TAILQ_HEAD(name, struct type,)

#define	TAILQ_HEAD_INITIALIZER(head)					\
	{ TAILQ_END(head), &(head).tqh_first }

#define	_TAILQ_ENTRY(type, qual)					\
struct {								\
	qual type *tqe_next;		/* next element */		\
	qual type *qual *tqe_prev;	/* address of previous next element */\
}
#define TAILQ_ENTRY(type)	_TAILQ_ENTRY(struct type,)

/*
 * Tail queue access methods.
 */
#define	TAILQ_FIRST(head)		((head)->tqh_first)
#define	TAILQ_END(head)			(NULL)
#define	TAILQ_NEXT(elm, field)		((elm)->field.tqe_next)
#define	TAILQ_LAST(head, headname) \
	(*(((struct headname *)(void *)((head)->tqh_last))->tqh_last))
#define	TAILQ_PREV(elm, headname, field) \
	(*(((struct headname *)(void *)((elm)->field.tqe_prev))->tqh_last))
#define	TAILQ_EMPTY(head)		(TAILQ_FIRST(head) == TAILQ_END(head))


#define	TAILQ_FOREACH(var, head, field)					\
	for ((var) = ((head)->tqh_first);				\
	    (var) != TAILQ_END(head);					\
	    (var) = ((var)->field.tqe_next))

#define	TAILQ_FOREACH_SAFE(var, head, field, next)			\
	for ((var) = ((head)->tqh_first);				\
	    (var) != TAILQ_END(head) &&					\
	    ((next) = TAILQ_NEXT(var, field), 1); (var) = (next))

#define	TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
	for ((var) = TAILQ_LAST((head), headname);			\
	    (var) != TAILQ_END(head);					\
	    (var) = TAILQ_PREV((var), headname, field))

#define	TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, prev)	\
	for ((var) = TAILQ_LAST((head), headname);			\
	    (var) != TAILQ_END(head) && 				\
	    ((prev) = TAILQ_PREV((var), headname, field), 1); (var) = (prev))

/*
 * Tail queue functions.
 */
#if defined(QUEUEDEBUG)
#define	QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)			\
	if ((head)->tqh_first &&					\
	    (head)->tqh_first->field.tqe_prev != &(head)->tqh_first)	\
		QUEUEDEBUG_ABORT("TAILQ_INSERT_HEAD %p %s:%d", (head),	\
		    __FILE__, __LINE__);
#define	QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)			\
	if (*(head)->tqh_last != NULL)					\
		QUEUEDEBUG_ABORT("TAILQ_INSERT_TAIL %p %s:%d", (head),	\
		    __FILE__, __LINE__);
#define	QUEUEDEBUG_TAILQ_OP(elm, field)					\
	if ((elm)->field.tqe_next &&					\
	    (elm)->field.tqe_next->field.tqe_prev !=			\
	    &(elm)->field.tqe_next)					\
		QUEUEDEBUG_ABORT("TAILQ_* forw %p %s:%d", (elm),	\
		    __FILE__, __LINE__);				\
	if (*(elm)->field.tqe_prev != (elm))				\
		QUEUEDEBUG_ABORT("TAILQ_* back %p %s:%d", (elm),	\
		    __FILE__, __LINE__);
#define	QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)			\
	if ((elm)->field.tqe_next == NULL &&				\
	    (head)->tqh_last != &(elm)->field.tqe_next)			\
		QUEUEDEBUG_ABORT("TAILQ_PREREMOVE head %p elm %p %s:%d",\
		    (head), (elm), __FILE__, __LINE__);
#define	QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)				\
	(elm)->field.tqe_next = (void *)1L;				\
	(elm)->field.tqe_prev = (void *)1L;
#else
#define	QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)
#define	QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)
#define	QUEUEDEBUG_TAILQ_OP(elm, field)
#define	QUEUEDEBUG_TAILQ_PREREMOVE(head, elm, field)
#define	QUEUEDEBUG_TAILQ_POSTREMOVE(elm, field)
#endif

#define	TAILQ_INIT(head) do {						\
	(head)->tqh_first = TAILQ_END(head);				\
	(head)->tqh_last = &(head)->tqh_first;				\
} while (/*CONSTCOND*/0)

#define	TAILQ_INSERT_HEAD(head, elm, field) do {			\
	QUEUEDEBUG_TAILQ_INSERT_HEAD((head), (elm), field)		\
	if (((elm)->field.tqe_next = (head)->tqh_first) != TAILQ_END(head))\
		(head)->tqh_first->field.tqe_prev =			\
		    &(elm)->field.tqe_next;				\
	else								\
		(head)->tqh_last = &(elm)->field.tqe_next;		\
	(head)->tqh_first = (elm);					\
	(elm)->field.tqe_prev = &(head)->tqh_first;			\
} while (/*CONSTCOND*/0)

#define	TAILQ_INSERT_TAIL(head, elm, field) do {			\
	QUEUEDEBUG_TAILQ_INSERT_TAIL((head), (elm), field)		\
	(elm)->field.tqe_next = TAILQ_END(head);			\
	(elm)->field.tqe_prev = (head)->tqh_last;			\
	*(head)->tqh_last = (elm);					\
	(head)->tqh_last = &(elm)->field.tqe_next;			\
} while (/*CONSTCOND*/0)

#define	TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	QUEUEDEBUG_TAILQ_OP((listelm), field)				\
	if (((elm)->field.tqe_next = (listelm)->field.tqe_next) != 	\
	    TAILQ_END(head))						\
		(elm)->field.tqe_next->field.tqe_prev = 		\
		    &(elm)->field.tqe_next;				\
	else								\
		(head)->tqh_last = &(elm)->field.tqe_next;		\
	(listelm)->field.tqe_next = (elm);				\
	(elm)->field.tqe_prev = &(listelm)->field.tqe_next;		\
} while (/*CONSTCOND*/0)

#define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
	QUEUEDEBUG_TAILQ_OP((listelm), field)				\
	(elm)->field.tqe_prev = (listelm)->field.tqe_prev;		\
	(elm)->field.tqe_next = (listelm);				\
	*(listelm)->field.tqe_prev = (elm);				\
	(listelm)->field.tqe_prev = &(elm)->field.tqe_next;		\
} while (/*CONSTCOND*/0)

#define	TAILQ_REMOVE(head, elm, field) do {				\
	QUEUEDEBUG_TAILQ_PREREMOVE((head), (elm), field)		\
	QUEUEDEBUG_TAILQ_OP((elm), field)				\
	if (((elm)->field.tqe_next) != TAILQ_END(head))			\
		(elm)->field.tqe_next->field.tqe_prev = 		\
		    (elm)->field.tqe_prev;				\
	else								\
		(head)->tqh_last = (elm)->field.tqe_prev;		\
	*(elm)->field.tqe_prev = (elm)->field.tqe_next;			\
	QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);			\
} while (/*CONSTCOND*/0)

#define TAILQ_REPLACE(head, elm, elm2, field) do {			\
        if (((elm2)->field.tqe_next = (elm)->field.tqe_next) != 	\
	    TAILQ_END(head))   						\
                (elm2)->field.tqe_next->field.tqe_prev =		\
                    &(elm2)->field.tqe_next;				\
        else								\
                (head)->tqh_last = &(elm2)->field.tqe_next;		\
        (elm2)->field.tqe_prev = (elm)->field.tqe_prev;			\
        *(elm2)->field.tqe_prev = (elm2);				\
	QUEUEDEBUG_TAILQ_POSTREMOVE((elm), field);			\
} while (/*CONSTCOND*/0)

#define	TAILQ_CONCAT(head1, head2, field) do {				\
	if (!TAILQ_EMPTY(head2)) {					\
		*(head1)->tqh_last = (head2)->tqh_first;		\
		(head2)->tqh_first->field.tqe_prev = (head1)->tqh_last;	\
		(head1)->tqh_last = (head2)->tqh_last;			\
		TAILQ_INIT((head2));					\
	}								\
} while (/*CONSTCOND*/0)

/*
 * Singly-linked Tail queue declarations.
 */
#define	STAILQ_HEAD(name, type)						\
struct name {								\
	struct type *stqh_first;	/* first element */		\
	struct type **stqh_last;	/* addr of last next element */	\
}

#define	STAILQ_HEAD_INITIALIZER(head)					\
	{ NULL, &(head).stqh_first }

#define	STAILQ_ENTRY(type)						\
struct {								\
	struct type *stqe_next;	/* next element */			\
}

/*
 * Singly-linked Tail queue access methods.
 */
#define	STAILQ_FIRST(head)	((head)->stqh_first)
#define	STAILQ_END(head)	NULL
#define	STAILQ_NEXT(elm, field)	((elm)->field.stqe_next)
#define	STAILQ_EMPTY(head)	(STAILQ_FIRST(head) == STAILQ_END(head))

/*
 * Singly-linked Tail queue functions.
 */
#define	STAILQ_INIT(head) do {						\
	(head)->stqh_first = NULL;					\
	(head)->stqh_last = &(head)->stqh_first;				\
} while (/*CONSTCOND*/0)

#define	STAILQ_INSERT_HEAD(head, elm, field) do {			\
	if (((elm)->field.stqe_next = (head)->stqh_first) == NULL)	\
		(head)->stqh_last = &(elm)->field.stqe_next;		\
	(head)->stqh_first = (elm);					\
} while (/*CONSTCOND*/0)

#define	STAILQ_INSERT_TAIL(head, elm, field) do {			\
	(elm)->field.stqe_next = NULL;					\
	*(head)->stqh_last = (elm);					\
	(head)->stqh_last = &(elm)->field.stqe_next;			\
} while (/*CONSTCOND*/0)

#define	STAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	if (((elm)->field.stqe_next = (listelm)->field.stqe_next) == NULL)\
		(head)->stqh_last = &(elm)->field.stqe_next;		\
	(listelm)->field.stqe_next = (elm);				\
} while (/*CONSTCOND*/0)

#define	STAILQ_REMOVE_HEAD(head, field) do {				\
	if (((head)->stqh_first = (head)->stqh_first->field.stqe_next) == NULL) \
		(head)->stqh_last = &(head)->stqh_first;			\
} while (/*CONSTCOND*/0)

#define	STAILQ_REMOVE(head, elm, type, field) do {			\
	if ((head)->stqh_first == (elm)) {				\
		STAILQ_REMOVE_HEAD((head), field);			\
	} else {							\
		struct type *curelm = (head)->stqh_first;		\
		while (curelm->field.stqe_next != (elm))			\
			curelm = curelm->field.stqe_next;		\
		if ((curelm->field.stqe_next =				\
			curelm->field.stqe_next->field.stqe_next) == NULL) \
			    (head)->stqh_last = &(curelm)->field.stqe_next; \
	}								\
} while (/*CONSTCOND*/0)

#define	STAILQ_FOREACH(var, head, field)				\
	for ((var) = ((head)->stqh_first);				\
		(var);							\
		(var) = ((var)->field.stqe_next))

#define	STAILQ_FOREACH_SAFE(var, head, field, tvar)			\
	for ((var) = STAILQ_FIRST((head));				\
	    (var) && ((tvar) = STAILQ_NEXT((var), field), 1);		\
	    (var) = (tvar))

#define	STAILQ_CONCAT(head1, head2) do {				\
	if (!STAILQ_EMPTY((head2))) {					\
		*(head1)->stqh_last = (head2)->stqh_first;		\
		(head1)->stqh_last = (head2)->stqh_last;		\
		STAILQ_INIT((head2));					\
	}								\
} while (/*CONSTCOND*/0)

#define	STAILQ_LAST(head, type, field)					\
	(STAILQ_EMPTY((head)) ?						\
		NULL :							\
	        ((struct type *)(void *)				\
		((char *)((head)->stqh_last) - offsetof(struct type, field))))


#ifndef _KERNEL
/*
 * Circular queue definitions. Do not use. We still keep the macros
 * for compatibility but because of pointer aliasing issues their use
 * is discouraged!
 */

/*
 * __launder_type():  We use this ugly hack to work around the the compiler
 * noticing that two types may not alias each other and elide tests in code.
 * We hit this in the CIRCLEQ macros when comparing 'struct name *' and
 * 'struct type *' (see CIRCLEQ_HEAD()).  Modern compilers (such as GCC
 * 4.8) declare these comparisons as always false, causing the code to
 * not run as designed.
 *
 * This hack is only to be used for comparisons and thus can be fully const.
 * Do not use for assignment.
 *
 * If we ever choose to change the ABI of the CIRCLEQ macros, we could fix
 * this by changing the head/tail sentinal values, but see the note above
 * this one.
 */
static __inline const void * __launder_type(const void *);
static __inline const void *
__launder_type(const void *__x)
{
	__asm __volatile("" : "+r" (__x));
	return __x;
}

#if defined(QUEUEDEBUG)
#define QUEUEDEBUG_CIRCLEQ_HEAD(head, field)				\
	if ((head)->cqh_first != CIRCLEQ_ENDC(head) &&			\
	    (head)->cqh_first->field.cqe_prev != CIRCLEQ_ENDC(head))	\
		QUEUEDEBUG_ABORT("CIRCLEQ head forw %p %s:%d", (head),	\
		      __FILE__, __LINE__);				\
	if ((head)->cqh_last != CIRCLEQ_ENDC(head) &&			\
	    (head)->cqh_last->field.cqe_next != CIRCLEQ_ENDC(head))	\
		QUEUEDEBUG_ABORT("CIRCLEQ head back %p %s:%d", (head),	\
		      __FILE__, __LINE__);
#define QUEUEDEBUG_CIRCLEQ_ELM(head, elm, field)			\
	if ((elm)->field.cqe_next == CIRCLEQ_ENDC(head)) {		\
		if ((head)->cqh_last != (elm))				\
			QUEUEDEBUG_ABORT("CIRCLEQ elm last %p %s:%d",	\
			    (elm), __FILE__, __LINE__);			\
	} else {							\
		if ((elm)->field.cqe_next->field.cqe_prev != (elm))	\
			QUEUEDEBUG_ABORT("CIRCLEQ elm forw %p %s:%d",	\
			    (elm), __FILE__, __LINE__);			\
	}								\
	if ((elm)->field.cqe_prev == CIRCLEQ_ENDC(head)) {		\
		if ((head)->cqh_first != (elm))				\
			QUEUEDEBUG_ABORT("CIRCLEQ elm first %p %s:%d",	\
			    (elm), __FILE__, __LINE__);			\
	} else {							\
		if ((elm)->field.cqe_prev->field.cqe_next != (elm))	\
			QUEUEDEBUG_ABORT("CIRCLEQ elm prev %p %s:%d",	\
			    (elm), __FILE__, __LINE__);			\
	}
#define QUEUEDEBUG_CIRCLEQ_POSTREMOVE(elm, field)			\
	(elm)->field.cqe_next = (void *)1L;				\
	(elm)->field.cqe_prev = (void *)1L;
#else
#define QUEUEDEBUG_CIRCLEQ_HEAD(head, field)
#define QUEUEDEBUG_CIRCLEQ_ELM(head, elm, field)
#define QUEUEDEBUG_CIRCLEQ_POSTREMOVE(elm, field)
#endif

#define	CIRCLEQ_HEAD(name, type)					\
struct name {								\
	struct type *cqh_first;		/* first element */		\
	struct type *cqh_last;		/* last element */		\
}

#define	CIRCLEQ_HEAD_INITIALIZER(head)					\
	{ CIRCLEQ_END(&head), CIRCLEQ_END(&head) }

#define	CIRCLEQ_ENTRY(type)						\
struct {								\
	struct type *cqe_next;		/* next element */		\
	struct type *cqe_prev;		/* previous element */		\
}

/*
 * Circular queue functions.
 */
#define	CIRCLEQ_INIT(head) do {						\
	(head)->cqh_first = CIRCLEQ_END(head);				\
	(head)->cqh_last = CIRCLEQ_END(head);				\
} while (/*CONSTCOND*/0)

#define	CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {		\
	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\
	QUEUEDEBUG_CIRCLEQ_ELM((head), (listelm), field)		\
	(elm)->field.cqe_next = (listelm)->field.cqe_next;		\
	(elm)->field.cqe_prev = (listelm);				\
	if ((listelm)->field.cqe_next == CIRCLEQ_ENDC(head))		\
		(head)->cqh_last = (elm);				\
	else								\
		(listelm)->field.cqe_next->field.cqe_prev = (elm);	\
	(listelm)->field.cqe_next = (elm);				\
} while (/*CONSTCOND*/0)

#define	CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {		\
	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\
	QUEUEDEBUG_CIRCLEQ_ELM((head), (listelm), field)		\
	(elm)->field.cqe_next = (listelm);				\
	(elm)->field.cqe_prev = (listelm)->field.cqe_prev;		\
	if ((listelm)->field.cqe_prev == CIRCLEQ_ENDC(head))		\
		(head)->cqh_first = (elm);				\
	else								\
		(listelm)->field.cqe_prev->field.cqe_next = (elm);	\
	(listelm)->field.cqe_prev = (elm);				\
} while (/*CONSTCOND*/0)

#define	CIRCLEQ_INSERT_HEAD(head, elm, field) do {			\
	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\
	(elm)->field.cqe_next = (head)->cqh_first;			\
	(elm)->field.cqe_prev = CIRCLEQ_END(head);			\
	if ((head)->cqh_last == CIRCLEQ_ENDC(head))			\
		(head)->cqh_last = (elm);				\
	else								\
		(head)->cqh_first->field.cqe_prev = (elm);		\
	(head)->cqh_first = (elm);					\
} while (/*CONSTCOND*/0)

#define	CIRCLEQ_INSERT_TAIL(head, elm, field) do {			\
	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\
	(elm)->field.cqe_next = CIRCLEQ_END(head);			\
	(elm)->field.cqe_prev = (head)->cqh_last;			\
	if ((head)->cqh_first == CIRCLEQ_ENDC(head))			\
		(head)->cqh_first = (elm);				\
	else								\
		(head)->cqh_last->field.cqe_next = (elm);		\
	(head)->cqh_last = (elm);					\
} while (/*CONSTCOND*/0)

#define	CIRCLEQ_REMOVE(head, elm, field) do {				\
	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\
	QUEUEDEBUG_CIRCLEQ_ELM((head), (elm), field)			\
	if ((elm)->field.cqe_next == CIRCLEQ_ENDC(head))		\
		(head)->cqh_last = (elm)->field.cqe_prev;		\
	else								\
		(elm)->field.cqe_next->field.cqe_prev =			\
		    (elm)->field.cqe_prev;				\
	if ((elm)->field.cqe_prev == CIRCLEQ_ENDC(head))		\
		(head)->cqh_first = (elm)->field.cqe_next;		\
	else								\
		(elm)->field.cqe_prev->field.cqe_next =			\
		    (elm)->field.cqe_next;				\
	QUEUEDEBUG_CIRCLEQ_POSTREMOVE((elm), field)			\
} while (/*CONSTCOND*/0)

#define	CIRCLEQ_FOREACH(var, head, field)				\
	for ((var) = ((head)->cqh_first);				\
		(var) != CIRCLEQ_ENDC(head);				\
		(var) = ((var)->field.cqe_next))

#define	CIRCLEQ_FOREACH_REVERSE(var, head, field)			\
	for ((var) = ((head)->cqh_last);				\
		(var) != CIRCLEQ_ENDC(head);				\
		(var) = ((var)->field.cqe_prev))

/*
 * Circular queue access methods.
 */
#define	CIRCLEQ_FIRST(head)		((head)->cqh_first)
#define	CIRCLEQ_LAST(head)		((head)->cqh_last)
/* For comparisons */
#define	CIRCLEQ_ENDC(head)		(__launder_type(head))
/* For assignments */
#define	CIRCLEQ_END(head)		((void *)(head))
#define	CIRCLEQ_NEXT(elm, field)	((elm)->field.cqe_next)
#define	CIRCLEQ_PREV(elm, field)	((elm)->field.cqe_prev)
#define	CIRCLEQ_EMPTY(head)						\
    (CIRCLEQ_FIRST(head) == CIRCLEQ_ENDC(head))

#define CIRCLEQ_LOOP_NEXT(head, elm, field)				\
	(((elm)->field.cqe_next == CIRCLEQ_ENDC(head))			\
	    ? ((head)->cqh_first)					\
	    : (elm->field.cqe_next))
#define CIRCLEQ_LOOP_PREV(head, elm, field)				\
	(((elm)->field.cqe_prev == CIRCLEQ_ENDC(head))			\
	    ? ((head)->cqh_last)					\
	    : (elm->field.cqe_prev))
#endif /* !_KERNEL */

#endif	/* !_SYS_QUEUE_H_ */