diff --git a/include/sys/Makefile b/include/sys/Makefile
index 6cc8f8bb2..37623982e 100644
--- a/include/sys/Makefile
+++ b/include/sys/Makefile
@@ -9,6 +9,6 @@ INCS=	asynchio.h dir.h file.h ioc_cmos.h ioc_disk.h \
 	select.h sem.h shm.h sigcontext.h signal.h socket.h \
 	soundcard.h statfs.h statvfs.h stat.h svrctl.h timeb.h \
 	time.h times.h types.h ucontext.h uio.h un.h utsname.h video.h vm.h \
-	wait.h cdefs.h 
+	wait.h cdefs.h null.h
 
 .include <bsd.kinc.mk>
diff --git a/include/sys/null.h b/include/sys/null.h
new file mode 100644
index 000000000..18836fcb8
--- /dev/null
+++ b/include/sys/null.h
@@ -0,0 +1,16 @@
+/*	$NetBSD: null.h,v 1.8 2009/10/13 17:19:00 dsl Exp $	*/
+
+#ifndef _SYS_NULL_H_
+#define _SYS_NULL_H_
+#ifndef	NULL
+#if !defined(__GNUG__) || __GNUG__ < 2 || (__GNUG__ == 2 && __GNUC_MINOR__ < 90)
+#if !defined(__cplusplus)
+#define	NULL	((void *)0)
+#else
+#define	NULL	0
+#endif /* !__cplusplus */
+#else
+#define	NULL	__null
+#endif
+#endif
+#endif /* _SYS_NULL_H_ */
diff --git a/include/sys/queue.h b/include/sys/queue.h
index 3a0a354c3..4c72a39dd 100644
--- a/include/sys/queue.h
+++ b/include/sys/queue.h
@@ -1,4 +1,6 @@
-/*-
+/*	$NetBSD: queue.h,v 1.52 2009/04/20 09:56:08 mschuett Exp $	*/
+
+/*
  * Copyright (c) 1991, 1993
  *	The Regents of the University of California.  All rights reserved.
  *
@@ -10,7 +12,7 @@
  * 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.
- * 4. Neither the name of the University nor the names of its contributors
+ * 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.
  *
@@ -27,38 +29,26 @@
  * SUCH DAMAGE.
  *
  *	@(#)queue.h	8.5 (Berkeley) 8/20/94
- * $FreeBSD$
  */
 
-#ifndef _SYS_QUEUE_H_
+#ifndef	_SYS_QUEUE_H_
 #define	_SYS_QUEUE_H_
 
-#include <sys/cdefs.h>
+#include <sys/null.h>
 
 /*
- * This file defines four types of data structures: singly-linked lists,
- * singly-linked tail queues, lists and tail queues.
+ * 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 singly-linked 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
- * 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, at the head of the list, or at the
- * end of the list. Elements being removed from the head of the tail queue
- * should use the explicit macro for this purpose for optimum efficiency.
- * A singly-linked tail queue may only be traversed in the forward direction.
- * Singly-linked tail queues are ideal for applications with large datasets
- * and few or no removals or for implementing a FIFO queue.
+ * 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
@@ -67,6 +57,13 @@
  * 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
@@ -74,243 +71,19 @@
  * 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.
- *
- *
- *				SLIST	LIST	STAILQ	TAILQ
- * _HEAD			+	+	+	+
- * _HEAD_INITIALIZER		+	+	+	+
- * _ENTRY			+	+	+	+
- * _INIT			+	+	+	+
- * _EMPTY			+	+	+	+
- * _FIRST			+	+	+	+
- * _NEXT			+	+	+	+
- * _PREV			-	-	-	+
- * _LAST			-	-	+	+
- * _FOREACH			+	+	+	+
- * _FOREACH_SAFE		+	+	+	+
- * _FOREACH_REVERSE		-	-	-	+
- * _FOREACH_REVERSE_SAFE	-	-	-	+
- * _INSERT_HEAD			+	+	+	+
- * _INSERT_BEFORE		-	+	-	+
- * _INSERT_AFTER		+	+	+	+
- * _INSERT_TAIL			-	-	+	+
- * _CONCAT			-	-	+	+
- * _REMOVE_HEAD			+	-	+	-
- * _REMOVE_NEXT			+	-	+	-
- * _REMOVE			+	+	+	+
- *
  */
-#ifdef QUEUE_MACRO_DEBUG
-/* Store the last 2 places the queue element or head was altered */
-struct qm_trace {
-	char * lastfile;
-	int lastline;
-	char * prevfile;
-	int prevline;
-};
-
-#define	TRACEBUF	struct qm_trace trace;
-#define	TRASHIT(x)	do {(x) = (void *)-1;} while (0)
-
-#define	QMD_TRACE_HEAD(head) do {					\
-	(head)->trace.prevline = (head)->trace.lastline;		\
-	(head)->trace.prevfile = (head)->trace.lastfile;		\
-	(head)->trace.lastline = __LINE__;				\
-	(head)->trace.lastfile = __FILE__;				\
-} while (0)
-
-#define	QMD_TRACE_ELEM(elem) do {					\
-	(elem)->trace.prevline = (elem)->trace.lastline;		\
-	(elem)->trace.prevfile = (elem)->trace.lastfile;		\
-	(elem)->trace.lastline = __LINE__;				\
-	(elem)->trace.lastfile = __FILE__;				\
-} while (0)
-
-#else
-#define	QMD_TRACE_ELEM(elem)
-#define	QMD_TRACE_HEAD(head)
-#define	TRACEBUF
-#define	TRASHIT(x)
-#endif	/* QUEUE_MACRO_DEBUG */
 
 /*
- * Singly-linked List declarations.
- */
-#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 functions.
- */
-#define	SLIST_EMPTY(head)	((head)->slh_first == NULL)
-
-#define	SLIST_FIRST(head)	((head)->slh_first)
-
-#define	SLIST_FOREACH(var, head, field)					\
-	for ((var) = SLIST_FIRST((head));				\
-	    (var);							\
-	    (var) = SLIST_NEXT((var), field))
-
-#define	SLIST_FOREACH_SAFE(var, head, field, tvar)			\
-	for ((var) = SLIST_FIRST((head));				\
-	    (var) && ((tvar) = SLIST_NEXT((var), field), 1);		\
-	    (var) = (tvar))
-
-#define	SLIST_FOREACH_PREVPTR(var, varp, head, field)			\
-	for ((varp) = &SLIST_FIRST((head));				\
-	    ((var) = *(varp)) != NULL;					\
-	    (varp) = &SLIST_NEXT((var), field))
-
-#define	SLIST_INIT(head) do {						\
-	SLIST_FIRST((head)) = NULL;					\
-} while (0)
-
-#define	SLIST_INSERT_AFTER(slistelm, elm, field) do {			\
-	SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);	\
-	SLIST_NEXT((slistelm), field) = (elm);				\
-} while (0)
-
-#define	SLIST_INSERT_HEAD(head, elm, field) do {			\
-	SLIST_NEXT((elm), field) = SLIST_FIRST((head));			\
-	SLIST_FIRST((head)) = (elm);					\
-} while (0)
-
-#define	SLIST_NEXT(elm, field)	((elm)->field.sle_next)
-
-#define	SLIST_REMOVE(head, elm, type, field) do {			\
-	if (SLIST_FIRST((head)) == (elm)) {				\
-		SLIST_REMOVE_HEAD((head), field);			\
-	}								\
-	else {								\
-		struct type *curelm = SLIST_FIRST((head));		\
-		while (SLIST_NEXT(curelm, field) != (elm))		\
-			curelm = SLIST_NEXT(curelm, field);		\
-		SLIST_REMOVE_NEXT(head, curelm, field);			\
-	}								\
-	TRASHIT((elm)->field.sle_next);					\
-} while (0)
-
-#define SLIST_REMOVE_NEXT(head, elm, field) do {				\
-	SLIST_NEXT(elm, field) =					\
-	    SLIST_NEXT(SLIST_NEXT(elm, field), field);			\
-} while (0)
-
-#define	SLIST_REMOVE_HEAD(head, field) do {				\
-	SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);	\
-} while (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 functions.
- */
-#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 (0)
-
-#define	STAILQ_EMPTY(head)	((head)->stqh_first == NULL)
-
-#define	STAILQ_FIRST(head)	((head)->stqh_first)
-
-#define	STAILQ_FOREACH(var, head, field)				\
-	for((var) = STAILQ_FIRST((head));				\
-	   (var);							\
-	   (var) = STAILQ_NEXT((var), field))
-
-
-#define	STAILQ_FOREACH_SAFE(var, head, field, tvar)			\
-	for ((var) = STAILQ_FIRST((head));				\
-	    (var) && ((tvar) = STAILQ_NEXT((var), field), 1);		\
-	    (var) = (tvar))
-
-#define	STAILQ_INIT(head) do {						\
-	STAILQ_FIRST((head)) = NULL;					\
-	(head)->stqh_last = &STAILQ_FIRST((head));			\
-} while (0)
-
-#define	STAILQ_INSERT_AFTER(head, tqelm, elm, field) do {		\
-	if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL)\
-		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
-	STAILQ_NEXT((tqelm), field) = (elm);				\
-} while (0)
-
-#define	STAILQ_INSERT_HEAD(head, elm, field) do {			\
-	if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL)	\
-		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
-	STAILQ_FIRST((head)) = (elm);					\
-} while (0)
-
-#define	STAILQ_INSERT_TAIL(head, elm, field) do {			\
-	STAILQ_NEXT((elm), field) = NULL;				\
-	*(head)->stqh_last = (elm);					\
-	(head)->stqh_last = &STAILQ_NEXT((elm), field);			\
-} while (0)
-
-#define	STAILQ_LAST(head, type, field)					\
-	(STAILQ_EMPTY((head)) ?						\
-		NULL :							\
-	        ((struct type *)(void *)				\
-		((char *)((head)->stqh_last) - __offsetof(struct type, field))))
-
-#define	STAILQ_NEXT(elm, field)	((elm)->field.stqe_next)
-
-#define	STAILQ_REMOVE(head, elm, type, field) do {			\
-	if (STAILQ_FIRST((head)) == (elm)) {				\
-		STAILQ_REMOVE_HEAD((head), field);			\
-	}								\
-	else {								\
-		struct type *curelm = STAILQ_FIRST((head));		\
-		while (STAILQ_NEXT(curelm, field) != (elm))		\
-			curelm = STAILQ_NEXT(curelm, field);		\
-		STAILQ_REMOVE_NEXT(head, curelm, field);		\
-	}								\
-	TRASHIT((elm)->field.stqe_next);				\
-} while (0)
-
-#define	STAILQ_REMOVE_HEAD(head, field) do {				\
-	if ((STAILQ_FIRST((head)) =					\
-	     STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)		\
-		(head)->stqh_last = &STAILQ_FIRST((head));		\
-} while (0)
-
-#define STAILQ_REMOVE_NEXT(head, elm, field) do {			\
-	if ((STAILQ_NEXT(elm, field) =					\
-	     STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)	\
-		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
-} while (0)
-
-/*
- * List declarations.
+ * List definitions.
  */
 #define	LIST_HEAD(name, type)						\
 struct name {								\
@@ -329,141 +102,463 @@ struct {								\
 /*
  * List functions.
  */
-
-#if (defined(_KERNEL) && defined(INVARIANTS))
-#define	QMD_LIST_CHECK_HEAD(head, field) do {				\
-	if (LIST_FIRST((head)) != NULL &&				\
-	    LIST_FIRST((head))->field.le_prev !=			\
-	     &LIST_FIRST((head)))					\
-		panic("Bad list head %p first->prev != head", (head));	\
-} while (0)
-
-#define	QMD_LIST_CHECK_NEXT(elm, field) do {				\
-	if (LIST_NEXT((elm), field) != NULL &&				\
-	    LIST_NEXT((elm), field)->field.le_prev !=			\
-	     &((elm)->field.le_next))					\
-	     	panic("Bad link elm %p next->prev != elm", (elm));	\
-} while (0)
-
-#define	QMD_LIST_CHECK_PREV(elm, field) do {				\
+#if defined(_KERNEL) && defined(QUEUEDEBUG)
+#define	QUEUEDEBUG_LIST_INSERT_HEAD(head, elm, field)			\
+	if ((head)->lh_first &&						\
+	    (head)->lh_first->field.le_prev != &(head)->lh_first)	\
+		panic("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)					\
+		panic("LIST_* forw %p %s:%d", (elm), __FILE__, __LINE__);\
 	if (*(elm)->field.le_prev != (elm))				\
-		panic("Bad link elm %p prev->next != elm", (elm));	\
-} while (0)
+		panic("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	QMD_LIST_CHECK_HEAD(head, field)
-#define	QMD_LIST_CHECK_NEXT(elm, field)
-#define	QMD_LIST_CHECK_PREV(elm, field)
-#endif /* (_KERNEL && INVARIANTS) */
-
-#define	LIST_EMPTY(head)	((head)->lh_first == NULL)
-
-#define	LIST_FIRST(head)	((head)->lh_first)
-
-#define	LIST_FOREACH(var, head, field)					\
-	for ((var) = LIST_FIRST((head));				\
-	    (var);							\
-	    (var) = LIST_NEXT((var), field))
-
-#define	LIST_FOREACH_SAFE(var, head, field, tvar)			\
-	for ((var) = LIST_FIRST((head));				\
-	    (var) && ((tvar) = LIST_NEXT((var), field), 1);		\
-	    (var) = (tvar))
+#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 {						\
-	LIST_FIRST((head)) = NULL;					\
-} while (0)
+	(head)->lh_first = NULL;					\
+} while (/*CONSTCOND*/0)
 
 #define	LIST_INSERT_AFTER(listelm, elm, field) do {			\
-	QMD_LIST_CHECK_NEXT(listelm, field);				\
-	if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)\
-		LIST_NEXT((listelm), field)->field.le_prev =		\
-		    &LIST_NEXT((elm), field);				\
-	LIST_NEXT((listelm), field) = (elm);				\
-	(elm)->field.le_prev = &LIST_NEXT((listelm), field);		\
-} while (0)
+	QUEUEDEBUG_LIST_OP((listelm), field)				\
+	if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)	\
+		(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 {			\
-	QMD_LIST_CHECK_PREV(listelm, field);				\
+	QUEUEDEBUG_LIST_OP((listelm), field)				\
 	(elm)->field.le_prev = (listelm)->field.le_prev;		\
-	LIST_NEXT((elm), field) = (listelm);				\
+	(elm)->field.le_next = (listelm);				\
 	*(listelm)->field.le_prev = (elm);				\
-	(listelm)->field.le_prev = &LIST_NEXT((elm), field);		\
-} while (0)
+	(listelm)->field.le_prev = &(elm)->field.le_next;		\
+} while (/*CONSTCOND*/0)
 
 #define	LIST_INSERT_HEAD(head, elm, field) do {				\
-	QMD_LIST_CHECK_HEAD((head), field);				\
-	if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)	\
-		LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);\
-	LIST_FIRST((head)) = (elm);					\
-	(elm)->field.le_prev = &LIST_FIRST((head));			\
-} while (0)
-
-#define	LIST_NEXT(elm, field)	((elm)->field.le_next)
+	QUEUEDEBUG_LIST_INSERT_HEAD((head), (elm), field)		\
+	if (((elm)->field.le_next = (head)->lh_first) != NULL)		\
+		(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 {					\
-	QMD_LIST_CHECK_NEXT(elm, field);				\
-	QMD_LIST_CHECK_PREV(elm, field);				\
-	if (LIST_NEXT((elm), field) != NULL)				\
-		LIST_NEXT((elm), field)->field.le_prev = 		\
+	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 = LIST_NEXT((elm), field);		\
-	TRASHIT((elm)->field.le_next);					\
-	TRASHIT((elm)->field.le_prev);					\
-} while (0)
+	*(elm)->field.le_prev = (elm)->field.le_next;			\
+	QUEUEDEBUG_LIST_POSTREMOVE((elm), field)			\
+} while (/*CONSTCOND*/0)
+
+#define	LIST_FOREACH(var, head, field)					\
+	for ((var) = ((head)->lh_first);				\
+		(var);							\
+		(var) = ((var)->field.le_next))
 
 /*
- * Tail queue declarations.
+ * List access methods.
  */
-#define	TAILQ_HEAD(name, type)						\
+#define	LIST_EMPTY(head)		((head)->lh_first == NULL)
+#define	LIST_FIRST(head)		((head)->lh_first)
+#define	LIST_NEXT(elm, field)		((elm)->field.le_next)
+
+
+/*
+ * Singly-linked List definitions.
+ */
+#define	SLIST_HEAD(name, type)						\
 struct name {								\
-	struct type *tqh_first;	/* first element */			\
-	struct type **tqh_last;	/* addr of last next element */		\
-	TRACEBUF							\
+	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 functions.
+ */
+#define	SLIST_INIT(head) do {						\
+	(head)->slh_first = NULL;					\
+} 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_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)
+
+#define	SLIST_REMOVE_AFTER(slistelm, field) do {			\
+	(slistelm)->field.sle_next =					\
+	    SLIST_NEXT(SLIST_NEXT((slistelm), field), field);		\
+} while (/*CONSTCOND*/0)
+
+#define	SLIST_FOREACH(var, head, field)					\
+	for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
+
+#define	SLIST_FOREACH_SAFE(var, head, field, tvar)			\
+	for ((var) = SLIST_FIRST((head));				\
+	    (var) && ((tvar) = SLIST_NEXT((var), field), 1);		\
+	    (var) = (tvar))
+
+/*
+ * Singly-linked List access methods.
+ */
+#define	SLIST_EMPTY(head)	((head)->slh_first == NULL)
+#define	SLIST_FIRST(head)	((head)->slh_first)
+#define	SLIST_NEXT(elm, field)	((elm)->field.sle_next)
+
+
+/*
+ * 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 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))))
+
+/*
+ * Singly-linked Tail queue access methods.
+ */
+#define	STAILQ_EMPTY(head)	((head)->stqh_first == NULL)
+#define	STAILQ_FIRST(head)	((head)->stqh_first)
+#define	STAILQ_NEXT(elm, field)	((elm)->field.stqe_next)
+
+
+/*
+ * 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 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(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_FOREACH(var, head, field)				\
+	for ((var) = ((head)->sqh_first);				\
+		(var);							\
+		(var) = ((var)->field.sqe_next))
+
+#define	SIMPLEQ_FOREACH_SAFE(var, head, field, next)			\
+	for ((var) = ((head)->sqh_first);				\
+		(var) && ((next = ((var)->field.sqe_next)), 1);		\
+		(var) = (next))
+
+#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))))
+
+/*
+ * Simple queue access methods.
+ */
+#define	SIMPLEQ_EMPTY(head)		((head)->sqh_first == NULL)
+#define	SIMPLEQ_FIRST(head)		((head)->sqh_first)
+#define	SIMPLEQ_NEXT(elm, field)	((elm)->field.sqe_next)
+
+
+/*
+ * 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)					\
 	{ NULL, &(head).tqh_first }
 
-#define	TAILQ_ENTRY(type)						\
+#define	_TAILQ_ENTRY(type, qual)					\
 struct {								\
-	struct type *tqe_next;	/* next element */			\
-	struct type **tqe_prev;	/* address of previous next element */	\
-	TRACEBUF							\
+	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 functions.
  */
-#if (defined(_KERNEL) && defined(INVARIANTS))
-#define	QMD_TAILQ_CHECK_HEAD(head, field) do {				\
-	if (!TAILQ_EMPTY(head) &&					\
-	    TAILQ_FIRST((head))->field.tqe_prev !=			\
-	     &TAILQ_FIRST((head)))					\
-		panic("Bad tailq head %p first->prev != head", (head));	\
-} while (0)
-
-#define	QMD_TAILQ_CHECK_TAIL(head, field) do {				\
+#if defined(_KERNEL) && defined(QUEUEDEBUG)
+#define	QUEUEDEBUG_TAILQ_INSERT_HEAD(head, elm, field)			\
+	if ((head)->tqh_first &&					\
+	    (head)->tqh_first->field.tqe_prev != &(head)->tqh_first)	\
+		panic("TAILQ_INSERT_HEAD %p %s:%d", (head), __FILE__, __LINE__);
+#define	QUEUEDEBUG_TAILQ_INSERT_TAIL(head, elm, field)			\
 	if (*(head)->tqh_last != NULL)					\
-	    	panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head)); 	\
-} while (0)
-
-#define	QMD_TAILQ_CHECK_NEXT(elm, field) do {				\
-	if (TAILQ_NEXT((elm), field) != NULL &&				\
-	    TAILQ_NEXT((elm), field)->field.tqe_prev !=			\
-	     &((elm)->field.tqe_next))					\
-		panic("Bad link elm %p next->prev != elm", (elm));	\
-} while (0)
-
-#define	QMD_TAILQ_CHECK_PREV(elm, field) do {				\
+		panic("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)					\
+		panic("TAILQ_* forw %p %s:%d", (elm), __FILE__, __LINE__);\
 	if (*(elm)->field.tqe_prev != (elm))				\
-		panic("Bad link elm %p prev->next != elm", (elm));	\
-} while (0)
+		panic("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)			\
+		panic("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	QMD_TAILQ_CHECK_HEAD(head, field)
-#define	QMD_TAILQ_CHECK_TAIL(head, headname)
-#define	QMD_TAILQ_CHECK_NEXT(elm, field)
-#define	QMD_TAILQ_CHECK_PREV(elm, field)
-#endif /* (_KERNEL && INVARIANTS) */
+#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 = NULL;					\
+	(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) != NULL)	\
+		(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 = NULL;					\
+	(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) != NULL)\
+		(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) != NULL)				\
+		(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_FOREACH(var, head, field)					\
+	for ((var) = ((head)->tqh_first);				\
+		(var);							\
+		(var) = ((var)->field.tqe_next))
+
+#define	TAILQ_FOREACH_SAFE(var, head, field, next)			\
+	for ((var) = ((head)->tqh_first);				\
+	        (var) != NULL && ((next) = TAILQ_NEXT(var, field), 1);	\
+		(var) = (next))
+
+#define	TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
+	for ((var) = (*(((struct headname *)((head)->tqh_last))->tqh_last));	\
+		(var);							\
+		(var) = (*(((struct headname *)((var)->field.tqe_prev))->tqh_last)))
+
+#define	TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, prev)	\
+	for ((var) = TAILQ_LAST((head), headname);			\
+		(var) && ((prev) = TAILQ_PREV((var), headname, field), 1);\
+		(var) = (prev))
 
 #define	TAILQ_CONCAT(head1, head2, field) do {				\
 	if (!TAILQ_EMPTY(head2)) {					\
@@ -471,157 +566,174 @@ struct {								\
 		(head2)->tqh_first->field.tqe_prev = (head1)->tqh_last;	\
 		(head1)->tqh_last = (head2)->tqh_last;			\
 		TAILQ_INIT((head2));					\
-		QMD_TRACE_HEAD(head1);					\
-		QMD_TRACE_HEAD(head2);					\
 	}								\
-} while (0)
-
-#define	TAILQ_EMPTY(head)	((head)->tqh_first == NULL)
-
-#define	TAILQ_FIRST(head)	((head)->tqh_first)
-
-#define	TAILQ_FOREACH(var, head, field)					\
-	for ((var) = TAILQ_FIRST((head));				\
-	    (var);							\
-	    (var) = TAILQ_NEXT((var), field))
-
-#define	TAILQ_FOREACH_SAFE(var, head, field, tvar)			\
-	for ((var) = TAILQ_FIRST((head));				\
-	    (var) && ((tvar) = TAILQ_NEXT((var), field), 1);		\
-	    (var) = (tvar))
-
-#define	TAILQ_FOREACH_REVERSE(var, head, headname, field)		\
-	for ((var) = TAILQ_LAST((head), headname);			\
-	    (var);							\
-	    (var) = TAILQ_PREV((var), headname, field))
-
-#define	TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)	\
-	for ((var) = TAILQ_LAST((head), headname);			\
-	    (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);	\
-	    (var) = (tvar))
-
-#define	TAILQ_INIT(head) do {						\
-	TAILQ_FIRST((head)) = NULL;					\
-	(head)->tqh_last = &TAILQ_FIRST((head));			\
-	QMD_TRACE_HEAD(head);						\
-} while (0)
-
-#define	TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
-	QMD_TAILQ_CHECK_NEXT(listelm, field);				\
-	if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)\
-		TAILQ_NEXT((elm), field)->field.tqe_prev = 		\
-		    &TAILQ_NEXT((elm), field);				\
-	else {								\
-		(head)->tqh_last = &TAILQ_NEXT((elm), field);		\
-		QMD_TRACE_HEAD(head);					\
-	}								\
-	TAILQ_NEXT((listelm), field) = (elm);				\
-	(elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);		\
-	QMD_TRACE_ELEM(&(elm)->field);					\
-	QMD_TRACE_ELEM(&listelm->field);				\
-} while (0)
-
-#define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
-	QMD_TAILQ_CHECK_PREV(listelm, field);				\
-	(elm)->field.tqe_prev = (listelm)->field.tqe_prev;		\
-	TAILQ_NEXT((elm), field) = (listelm);				\
-	*(listelm)->field.tqe_prev = (elm);				\
-	(listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);		\
-	QMD_TRACE_ELEM(&(elm)->field);					\
-	QMD_TRACE_ELEM(&listelm->field);				\
-} while (0)
-
-#define	TAILQ_INSERT_HEAD(head, elm, field) do {			\
-	QMD_TAILQ_CHECK_HEAD(head, field);				\
-	if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)	\
-		TAILQ_FIRST((head))->field.tqe_prev =			\
-		    &TAILQ_NEXT((elm), field);				\
-	else								\
-		(head)->tqh_last = &TAILQ_NEXT((elm), field);		\
-	TAILQ_FIRST((head)) = (elm);					\
-	(elm)->field.tqe_prev = &TAILQ_FIRST((head));			\
-	QMD_TRACE_HEAD(head);						\
-	QMD_TRACE_ELEM(&(elm)->field);					\
-} while (0)
-
-#define	TAILQ_INSERT_TAIL(head, elm, field) do {			\
-	QMD_TAILQ_CHECK_TAIL(head, field);				\
-	TAILQ_NEXT((elm), field) = NULL;				\
-	(elm)->field.tqe_prev = (head)->tqh_last;			\
-	*(head)->tqh_last = (elm);					\
-	(head)->tqh_last = &TAILQ_NEXT((elm), field);			\
-	QMD_TRACE_HEAD(head);						\
-	QMD_TRACE_ELEM(&(elm)->field);					\
-} while (0)
-
-#define	TAILQ_LAST(head, headname)					\
-	(*(((struct headname *)((head)->tqh_last))->tqh_last))
-
-#define	TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)
-
-#define	TAILQ_PREV(elm, headname, field)				\
-	(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
-
-#define	TAILQ_REMOVE(head, elm, field) do {				\
-	QMD_TAILQ_CHECK_NEXT(elm, field);				\
-	QMD_TAILQ_CHECK_PREV(elm, field);				\
-	if ((TAILQ_NEXT((elm), field)) != NULL)				\
-		TAILQ_NEXT((elm), field)->field.tqe_prev = 		\
-		    (elm)->field.tqe_prev;				\
-	else {								\
-		(head)->tqh_last = (elm)->field.tqe_prev;		\
-		QMD_TRACE_HEAD(head);					\
-	}								\
-	*(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);		\
-	TRASHIT((elm)->field.tqe_next);					\
-	TRASHIT((elm)->field.tqe_prev);					\
-	QMD_TRACE_ELEM(&(elm)->field);					\
-} while (0)
-
-
-#ifdef _KERNEL
+} while (/*CONSTCOND*/0)
 
 /*
- * XXX insque() and remque() are an old way of handling certain queues.
- * They bogusly assumes that all queue heads look alike.
+ * Tail queue access methods.
  */
+#define	TAILQ_EMPTY(head)		((head)->tqh_first == NULL)
+#define	TAILQ_FIRST(head)		((head)->tqh_first)
+#define	TAILQ_NEXT(elm, field)		((elm)->field.tqe_next)
 
-struct quehead {
-	struct quehead *qh_link;
-	struct quehead *qh_rlink;
-};
+#define	TAILQ_LAST(head, headname) \
+	(*(((struct headname *)((head)->tqh_last))->tqh_last))
+#define	TAILQ_PREV(elm, headname, field) \
+	(*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
 
-#ifdef __CC_SUPPORTS___INLINE
 
-static __inline void
-insque(void *a, void *b)
-{
-	struct quehead *element = (struct quehead *)a,
-		 *head = (struct quehead *)b;
+/*
+ * Circular queue definitions.
+ */
+#if defined(_KERNEL) && defined(QUEUEDEBUG)
+#define QUEUEDEBUG_CIRCLEQ_HEAD(head, field)				\
+	if ((head)->cqh_first != (void *)(head) &&			\
+	    (head)->cqh_first->field.cqe_prev != (void *)(head))	\
+		panic("CIRCLEQ head forw %p %s:%d", (head),		\
+		      __FILE__, __LINE__);				\
+	if ((head)->cqh_last != (void *)(head) &&			\
+	    (head)->cqh_last->field.cqe_next != (void *)(head))		\
+		panic("CIRCLEQ head back %p %s:%d", (head),		\
+		      __FILE__, __LINE__);
+#define QUEUEDEBUG_CIRCLEQ_ELM(head, elm, field)			\
+	if ((elm)->field.cqe_next == (void *)(head)) {			\
+		if ((head)->cqh_last != (elm))				\
+			panic("CIRCLEQ elm last %p %s:%d", (elm),	\
+			      __FILE__, __LINE__);			\
+	} else {							\
+		if ((elm)->field.cqe_next->field.cqe_prev != (elm))	\
+			panic("CIRCLEQ elm forw %p %s:%d", (elm),	\
+			      __FILE__, __LINE__);			\
+	}								\
+	if ((elm)->field.cqe_prev == (void *)(head)) {			\
+		if ((head)->cqh_first != (elm))				\
+			panic("CIRCLEQ elm first %p %s:%d", (elm),	\
+			      __FILE__, __LINE__);			\
+	} else {							\
+		if ((elm)->field.cqe_prev->field.cqe_next != (elm))	\
+			panic("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
 
-	element->qh_link = head->qh_link;
-	element->qh_rlink = head;
-	head->qh_link = element;
-	element->qh_link->qh_rlink = element;
+#define	CIRCLEQ_HEAD(name, type)					\
+struct name {								\
+	struct type *cqh_first;		/* first element */		\
+	struct type *cqh_last;		/* last element */		\
 }
 
-static __inline void
-remque(void *a)
-{
-	struct quehead *element = (struct quehead *)a;
+#define	CIRCLEQ_HEAD_INITIALIZER(head)					\
+	{ (void *)&head, (void *)&head }
 
-	element->qh_link->qh_rlink = element->qh_rlink;
-	element->qh_rlink->qh_link = element->qh_link;
-	element->qh_rlink = 0;
+#define	CIRCLEQ_ENTRY(type)						\
+struct {								\
+	struct type *cqe_next;		/* next element */		\
+	struct type *cqe_prev;		/* previous element */		\
 }
 
-#else /* !__CC_SUPPORTS___INLINE */
+/*
+ * Circular queue functions.
+ */
+#define	CIRCLEQ_INIT(head) do {						\
+	(head)->cqh_first = (void *)(head);				\
+	(head)->cqh_last = (void *)(head);				\
+} while (/*CONSTCOND*/0)
 
-void	insque(void *a, void *b);
-void	remque(void *a);
+#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 == (void *)(head))		\
+		(head)->cqh_last = (elm);				\
+	else								\
+		(listelm)->field.cqe_next->field.cqe_prev = (elm);	\
+	(listelm)->field.cqe_next = (elm);				\
+} while (/*CONSTCOND*/0)
 
-#endif /* __CC_SUPPORTS___INLINE */
+#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 == (void *)(head))		\
+		(head)->cqh_first = (elm);				\
+	else								\
+		(listelm)->field.cqe_prev->field.cqe_next = (elm);	\
+	(listelm)->field.cqe_prev = (elm);				\
+} while (/*CONSTCOND*/0)
 
-#endif /* _KERNEL */
+#define	CIRCLEQ_INSERT_HEAD(head, elm, field) do {			\
+	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\
+	(elm)->field.cqe_next = (head)->cqh_first;			\
+	(elm)->field.cqe_prev = (void *)(head);				\
+	if ((head)->cqh_last == (void *)(head))				\
+		(head)->cqh_last = (elm);				\
+	else								\
+		(head)->cqh_first->field.cqe_prev = (elm);		\
+	(head)->cqh_first = (elm);					\
+} while (/*CONSTCOND*/0)
 
-#endif /* !_SYS_QUEUE_H_ */
+#define	CIRCLEQ_INSERT_TAIL(head, elm, field) do {			\
+	QUEUEDEBUG_CIRCLEQ_HEAD((head), field)				\
+	(elm)->field.cqe_next = (void *)(head);				\
+	(elm)->field.cqe_prev = (head)->cqh_last;			\
+	if ((head)->cqh_first == (void *)(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 == (void *)(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 == (void *)(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) != (const void *)(head);				\
+		(var) = ((var)->field.cqe_next))
+
+#define	CIRCLEQ_FOREACH_REVERSE(var, head, field)			\
+	for ((var) = ((head)->cqh_last);				\
+		(var) != (const void *)(head);				\
+		(var) = ((var)->field.cqe_prev))
+
+/*
+ * Circular queue access methods.
+ */
+#define	CIRCLEQ_EMPTY(head)		((head)->cqh_first == (void *)(head))
+#define	CIRCLEQ_FIRST(head)		((head)->cqh_first)
+#define	CIRCLEQ_LAST(head)		((head)->cqh_last)
+#define	CIRCLEQ_NEXT(elm, field)	((elm)->field.cqe_next)
+#define	CIRCLEQ_PREV(elm, field)	((elm)->field.cqe_prev)
+
+#define CIRCLEQ_LOOP_NEXT(head, elm, field)				\
+	(((elm)->field.cqe_next == (void *)(head))			\
+	    ? ((head)->cqh_first)					\
+	    : (elm->field.cqe_next))
+#define CIRCLEQ_LOOP_PREV(head, elm, field)				\
+	(((elm)->field.cqe_prev == (void *)(head))			\
+	    ? ((head)->cqh_last)					\
+	    : (elm->field.cqe_prev))
+
+#endif	/* !_SYS_QUEUE_H_ */