fetch queue.h from latest freebsd cvs

include/sys/queue.h

@@ -1,4 +1,4 @@
-/*
+/*-
  * Copyright (c) 1991, 1993
  *	The Regents of the University of California.  All rights reserved.
  *
@@ -10,7 +10,7 @@
  * 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.
- * 3. Neither the name of the University nor the names of its contributors
+ * 4. 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.
  *
@@ -27,24 +27,38 @@
  * SUCH DAMAGE.
  *
  *	@(#)queue.h	8.5 (Berkeley) 8/20/94
+ * $FreeBSD: src/sys/sys/queue.h,v 1.68 2006/10/24 11:20:29 ru Exp $
  */
 
-#ifndef	_SYS_QUEUE_H_
+#ifndef _SYS_QUEUE_H_
 #define	_SYS_QUEUE_H_
 
+#include <sys/cdefs.h>
+
 /*
- * This file defines five types of data structures: singly-linked lists,
- * lists, simple queues, tail queues, and circular queues.
+ * This file defines four types of data structures: singly-linked lists,
+ * singly-linked tail queues, lists and tail 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 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 list is headed by a single forward pointer (or an array of forward
  * pointers for a hash table header). The elements are doubly linked
@@ -53,13 +67,6 @@
  * 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
@@ -67,85 +74,67 @@
  * 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			+	+	+	+
+ *
  */
+#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 */
 
 /*
- * 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 functions.
- */
-#define	LIST_INIT(head) do {						\
-	(head)->lh_first = NULL;					\
-} while (/*CONSTCOND*/0)
-
-#define	LIST_INSERT_AFTER(listelm, elm, field) do {			\
-	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 {			\
-	(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 {				\
-	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 {					\
-	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;			\
-} while (/*CONSTCOND*/0)
-
-#define	LIST_FOREACH(var, head, field)					\
-	for ((var) = ((head)->lh_first);				\
-		(var);							\
-		(var) = ((var)->field.le_next))
-
-/*
- * List access methods.
- */
-#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.
+ * Singly-linked List declarations.
  */
 #define	SLIST_HEAD(name, type)						\
 struct name {								\
@@ -163,55 +152,66 @@ struct {								\
 /*
  * 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 {						\
-	(head)->slh_first = NULL;					\
-} while (/*CONSTCOND*/0)
+	SLIST_FIRST((head)) = NULL;					\
+} while (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)
+	SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);	\
+	SLIST_NEXT((slistelm), field) = (elm);				\
+} while (0)
 
 #define	SLIST_INSERT_HEAD(head, elm, field) do {			\
-	(elm)->field.sle_next = (head)->slh_first;			\
-	(head)->slh_first = (elm);					\
-} while (/*CONSTCOND*/0)
+	SLIST_NEXT((elm), field) = SLIST_FIRST((head));			\
+	SLIST_FIRST((head)) = (elm);					\
+} while (0)
 
-#define	SLIST_REMOVE_HEAD(head, field) do {				\
-	(head)->slh_first = (head)->slh_first->field.sle_next;		\
-} while (/*CONSTCOND*/0)
+#define	SLIST_NEXT(elm, field)	((elm)->field.sle_next)
 
 #define	SLIST_REMOVE(head, elm, type, field) do {			\
-	if ((head)->slh_first == (elm)) {				\
+	if (SLIST_FIRST((head)) == (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;		\
+		struct type *curelm = SLIST_FIRST((head));		\
+		while (SLIST_NEXT(curelm, field) != (elm))		\
+			curelm = SLIST_NEXT(curelm, field);		\
+		SLIST_NEXT(curelm, field) =				\
+		    SLIST_NEXT(SLIST_NEXT(curelm, field), field);	\
 	}								\
-} while (/*CONSTCOND*/0)
-
-#define	SLIST_FOREACH(var, head, field)					\
-	for((var) = (head)->slh_first; (var); (var) = (var)->field.sle_next)
-
-/*
- * 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)
+	TRASHIT((elm)->field.sle_next);					\
+} 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)					\
+#define	STAILQ_HEAD(name, type)						\
 struct name {								\
-	struct type *stqh_first;	/* first element */			\
-	struct type **stqh_last;	/* addr of last next element */		\
+	struct type *stqh_first;/* first element */			\
+	struct type **stqh_last;/* addr of last next element */		\
 }
 
 #define	STAILQ_HEAD_INITIALIZER(head)					\
@@ -225,333 +225,394 @@ struct {								\
 /*
  * 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 {						\
-	(head)->stqh_first = NULL;					\
-	(head)->stqh_last = &(head)->stqh_first;				\
-} while (/*CONSTCOND*/0)
+	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 (((elm)->field.stqe_next = (head)->stqh_first) == NULL)	\
-		(head)->stqh_last = &(elm)->field.stqe_next;		\
-	(head)->stqh_first = (elm);					\
-} while (/*CONSTCOND*/0)
+	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 {			\
-	(elm)->field.stqe_next = NULL;					\
+	STAILQ_NEXT((elm), field) = NULL;				\
 	*(head)->stqh_last = (elm);					\
-	(head)->stqh_last = &(elm)->field.stqe_next;			\
-} while (/*CONSTCOND*/0)
+	(head)->stqh_last = &STAILQ_NEXT((elm), field);			\
+} while (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_LAST(head, type, field)					\
+	(STAILQ_EMPTY((head)) ?						\
+		NULL :							\
+	        ((struct type *)(void *)				\
+		((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 
-#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_NEXT(elm, field)	((elm)->field.stqe_next)
 
 #define	STAILQ_REMOVE(head, elm, type, field) do {			\
-	if ((head)->stqh_first == (elm)) {				\
+	if (STAILQ_FIRST((head)) == (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))
-
-/*
- * 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)
+	else {								\
+		struct type *curelm = STAILQ_FIRST((head));		\
+		while (STAILQ_NEXT(curelm, field) != (elm))		\
+			curelm = STAILQ_NEXT(curelm, field);		\
+		if ((STAILQ_NEXT(curelm, field) =			\
+		     STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL)\
+			(head)->stqh_last = &STAILQ_NEXT((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)
 
 /*
- * Simple queue definitions.
+ * List declarations.
  */
-#define	SIMPLEQ_HEAD(name, type)					\
+#define	LIST_HEAD(name, type)						\
 struct name {								\
-	struct type *sqh_first;	/* first element */			\
-	struct type **sqh_last;	/* addr of last next element */		\
+	struct type *lh_first;	/* first element */			\
 }
 
-#define	SIMPLEQ_HEAD_INITIALIZER(head)					\
-	{ NULL, &(head).sqh_first }
+#define	LIST_HEAD_INITIALIZER(head)					\
+	{ NULL }
 
-#define	SIMPLEQ_ENTRY(type)						\
+#define	LIST_ENTRY(type)						\
 struct {								\
-	struct type *sqe_next;	/* next element */			\
+	struct type *le_next;	/* next element */			\
+	struct type **le_prev;	/* address of previous next element */	\
 }
 
 /*
- * Simple queue functions.
+ * List 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))
+#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 (*(elm)->field.le_prev != (elm))				\
+		panic("Bad link elm %p prev->next != elm", (elm));	\
+} while (0)
+#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)
 
-/*
- * 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)
+#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	LIST_INIT(head) do {						\
+	LIST_FIRST((head)) = NULL;					\
+} while (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)
+
+#define	LIST_INSERT_BEFORE(listelm, elm, field) do {			\
+	QMD_LIST_CHECK_PREV(listelm, field);				\
+	(elm)->field.le_prev = (listelm)->field.le_prev;		\
+	LIST_NEXT((elm), field) = (listelm);				\
+	*(listelm)->field.le_prev = (elm);				\
+	(listelm)->field.le_prev = &LIST_NEXT((elm), field);		\
+} while (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)
+
+#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 = 		\
+		    (elm)->field.le_prev;				\
+	*(elm)->field.le_prev = LIST_NEXT((elm), field);		\
+	TRASHIT((elm)->field.le_next);					\
+	TRASHIT((elm)->field.le_prev);					\
+} while (0)
 
 /*
- * Tail queue definitions.
+ * Tail queue declarations.
  */
-#define	_TAILQ_HEAD(name, type, qual)					\
+#define	TAILQ_HEAD(name, type)						\
 struct name {								\
-	qual type *tqh_first;		/* first element */		\
-	qual type *qual *tqh_last;	/* addr of last next element */	\
+	struct type *tqh_first;	/* first element */			\
+	struct type **tqh_last;	/* addr of last next element */		\
+	TRACEBUF							\
 }
-#define TAILQ_HEAD(name, type)	_TAILQ_HEAD(name, struct type,)
 
 #define	TAILQ_HEAD_INITIALIZER(head)					\
 	{ NULL, &(head).tqh_first }
 
-#define	_TAILQ_ENTRY(type, qual)					\
+#define	TAILQ_ENTRY(type)						\
 struct {								\
-	qual type *tqe_next;		/* next element */		\
-	qual type *qual *tqe_prev;	/* address of previous next element */\
+	struct type *tqe_next;	/* next element */			\
+	struct type **tqe_prev;	/* address of previous next element */	\
+	TRACEBUF							\
 }
-#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 (*(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 {				\
+	if (*(elm)->field.tqe_prev != (elm))				\
+		panic("Bad link elm %p prev->next != elm", (elm));	\
+} while (0)
+#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	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));					\
+		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 {						\
-	(head)->tqh_first = NULL;					\
-	(head)->tqh_last = &(head)->tqh_first;				\
-} while (/*CONSTCOND*/0)
+	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 {			\
-	if (((elm)->field.tqe_next = (head)->tqh_first) != NULL)	\
-		(head)->tqh_first->field.tqe_prev =			\
-		    &(elm)->field.tqe_next;				\
+	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 = &(elm)->field.tqe_next;		\
-	(head)->tqh_first = (elm);					\
-	(elm)->field.tqe_prev = &(head)->tqh_first;			\
-} while (/*CONSTCOND*/0)
+		(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 {			\
-	(elm)->field.tqe_next = NULL;					\
+	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 = &(elm)->field.tqe_next;			\
-} while (/*CONSTCOND*/0)
+	(head)->tqh_last = &TAILQ_NEXT((elm), field);			\
+	QMD_TRACE_HEAD(head);						\
+	QMD_TRACE_ELEM(&(elm)->field);					\
+} while (0)
 
-#define	TAILQ_INSERT_AFTER(head, listelm, elm, field) do {		\
-	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_LAST(head, headname)					\
+	(*(((struct headname *)((head)->tqh_last))->tqh_last))
 
-#define	TAILQ_INSERT_BEFORE(listelm, elm, field) do {			\
-	(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_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 {				\
-	if (((elm)->field.tqe_next) != NULL)				\
-		(elm)->field.tqe_next->field.tqe_prev = 		\
+	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								\
+	else {								\
 		(head)->tqh_last = (elm)->field.tqe_prev;		\
-	*(elm)->field.tqe_prev = (elm)->field.tqe_next;			\
-} while (/*CONSTCOND*/0)
+		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)
 
-#define	TAILQ_FOREACH(var, head, field)					\
-	for ((var) = ((head)->tqh_first);				\
-		(var);							\
-		(var) = ((var)->field.tqe_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)))
+#ifdef _KERNEL
 
 /*
- * Tail queue access methods.
+ * XXX insque() and remque() are an old way of handling certain queues.
+ * They bogusly assumes that all queue heads look alike.
  */
-#define	TAILQ_EMPTY(head)		((head)->tqh_first == NULL)
-#define	TAILQ_FIRST(head)		((head)->tqh_first)
-#define	TAILQ_NEXT(elm, field)		((elm)->field.tqe_next)
 
-#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))
+struct quehead {
+	struct quehead *qh_link;
+	struct quehead *qh_rlink;
+};
 
+#ifdef __CC_SUPPORTS___INLINE
 
-/*
- * Circular queue definitions.
- */
-#define	CIRCLEQ_HEAD(name, type)					\
-struct name {								\
-	struct type *cqh_first;		/* first element */		\
-	struct type *cqh_last;		/* last element */		\
+static __inline void
+insque(void *a, void *b)
+{
+	struct quehead *element = (struct quehead *)a,
+		 *head = (struct quehead *)b;
+
+	element->qh_link = head->qh_link;
+	element->qh_rlink = head;
+	head->qh_link = element;
+	element->qh_link->qh_rlink = element;
 }
 
-#define	CIRCLEQ_HEAD_INITIALIZER(head)					\
-	{ (void *)&head, (void *)&head }
+static __inline void
+remque(void *a)
+{
+	struct quehead *element = (struct quehead *)a;
 
-#define	CIRCLEQ_ENTRY(type)						\
-struct {								\
-	struct type *cqe_next;		/* next element */		\
-	struct type *cqe_prev;		/* previous element */		\
+	element->qh_link->qh_rlink = element->qh_rlink;
+	element->qh_rlink->qh_link = element->qh_link;
+	element->qh_rlink = 0;
 }
 
-/*
- * Circular queue functions.
- */
-#define	CIRCLEQ_INIT(head) do {						\
-	(head)->cqh_first = (void *)(head);				\
-	(head)->cqh_last = (void *)(head);				\
-} while (/*CONSTCOND*/0)
-
-#define	CIRCLEQ_INSERT_AFTER(head, listelm, elm, field) do {		\
-	(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)
-
-#define	CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field) do {		\
-	(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)
-
-#define	CIRCLEQ_INSERT_HEAD(head, elm, field) do {			\
-	(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)
-
-#define	CIRCLEQ_INSERT_TAIL(head, elm, field) do {			\
-	(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)
+#else /* !__CC_SUPPORTS___INLINE */
 
-#define	CIRCLEQ_REMOVE(head, elm, field) do {				\
-	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;				\
-} while (/*CONSTCOND*/0)
+void	insque(void *a, void *b);
+void	remque(void *a);
 
-#define	CIRCLEQ_FOREACH(var, head, field)				\
-	for ((var) = ((head)->cqh_first);				\
-		(var) != (const void *)(head);				\
-		(var) = ((var)->field.cqe_next))
+#endif /* __CC_SUPPORTS___INLINE */
 
-#define	CIRCLEQ_FOREACH_REVERSE(var, head, field)			\
-	for ((var) = ((head)->cqh_last);				\
-		(var) != (const void *)(head);				\
-		(var) = ((var)->field.cqe_prev))
+#endif /* _KERNEL */
 
-/*
- * 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 */
+#endif /* !_SYS_QUEUE_H_ */