From: Manfred Spraul <manfred@colorfullife.com>

A list_del debugging check.  Has been in -mm for over three years.  davej
thinks it'd be useful for mainline.

Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 include/linux/list.h |    4 ++++
 1 file changed, 4 insertions(+)

diff -puN include/linux/list.h~list_del-debug include/linux/list.h
--- a/include/linux/list.h~list_del-debug
+++ a/include/linux/list.h
@@ -6,7 +6,9 @@
 #include <linux/stddef.h>
 #include <linux/poison.h>
 #include <linux/prefetch.h>
+#include <linux/kernel.h>
 #include <asm/system.h>
+#include <asm/bug.h>
 
 /*
  * Simple doubly linked list implementation.
@@ -167,6 +169,8 @@ static inline void __list_del(struct lis
 #ifndef CONFIG_DEBUG_LIST
 static inline void list_del(struct list_head *entry)
 {
+	BUG_ON(entry->prev->next != entry);
+	BUG_ON(entry->next->prev != entry);
 	__list_del(entry->prev, entry->next);
 	entry->next = LIST_POISON1;
 	entry->prev = LIST_POISON2;
_