diff --git a/sys/sys/queue.h b/sys/sys/queue.h
--- a/sys/sys/queue.h
+++ b/sys/sys/queue.h
@@ -355,11 +355,6 @@
 		    "first field address", (head), (head)->stqh_last);	\
 } while (0)
 
-#define	STAILQ_ASSERT_EMPTY(head) do {					\
-	if (!STAILQ_EMPTY((head)))					\
-		panic("stailq %p is not empty", (head));		\
-} while (0)
-
 /*
  * QMD_STAILQ_CHECK_TAIL(STAILQ_HEAD *head)
  *
@@ -370,11 +365,23 @@
 		panic("Stailq %p last element's next pointer is %p, "	\
 		    "not NULL", (head), *(head)->stqh_last);		\
 } while (0)
+
+#define	STAILQ_ASSERT_EMPTY(head) do {					\
+	if (!STAILQ_EMPTY((head)))					\
+		panic("stailq %p is not empty", (head));		\
+} while (0);
+
+#define	STAILQ_ASSERT_NONEMPTY(head) do {				\
+	if (STAILQ_EMPTY((head)))					\
+		panic("stailq %p is empty", (head));			\
+} while (0);
+
 #else
 #define	QMD_STAILQ_CHECK_EMPTY(head)
-#define	STAILQ_ASSERT_EMPTY(head)
 #define	QMD_STAILQ_CHECK_TAIL(head)
-#endif /* (_KERNEL && INVARIANTS) */
+#define	STAILQ_ASSERT_EMPTY(head)
+#define	STAILQ_ASSERT_NONEMPTY(head)
+#endif /* _KERNEL && INVARIANTS */
 
 #define	STAILQ_CONCAT(head1, head2) do {				\
 	if (!STAILQ_EMPTY((head2))) {					\
@@ -472,6 +479,19 @@
 		(head)->stqh_last = &STAILQ_FIRST((head));		\
 } while (0)
 
+#define STAILQ_SPLIT_AFTER(head, elm, rest, field) do {			\
+	STAILQ_ASSERT_NONEMPTY((head));					\
+	if (&STAILQ_NEXT((elm), field) == (head)->stqh_last)		\
+		/* 'elm' is the last element in 'head'. */		\
+		STAILQ_INIT((rest));					\
+	else {								\
+		STAILQ_FIRST((rest)) = STAILQ_NEXT((elm), field);	\
+		(rest)->stqh_last = (head)->stqh_last;			\
+		STAILQ_NEXT((elm), field) = NULL;			\
+		(head)->stqh_last = &STAILQ_NEXT((elm), field);		\
+	}								\
+} while (0)
+
 #define STAILQ_SWAP(head1, head2, type) do {				\
 	QUEUE_TYPEOF(type) *swap_first = STAILQ_FIRST(head1);		\
 	QUEUE_TYPEOF(type) **swap_last = (head1)->stqh_last;		\