[PATCH 2/2] list: DEBUG_LIST for hlist

[Akinobu Mita <akinobu.mita@gmail.com>]

Add sanity checks in hlist manipulation when CONFIG_DEBUG_LIST is enabled.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
 include/linux/list.h |   18 ++++++++++++++++++
 lib/list_debug.c     |   38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)

Index: 2.6/include/linux/list.h
===================================================================
--- 2.6.orig/include/linux/list.h
+++ 2.6/include/linux/list.h
@@ -564,6 +564,12 @@ static inline int hlist_empty(const stru
 	return !h->first;
 }
 
+#ifdef CONFIG_DEBUG_LIST
+
+extern void __hlist_del(struct hlist_node *n);
+
+#else
+
 static inline void __hlist_del(struct hlist_node *n)
 {
 	struct hlist_node *next = n->next;
@@ -573,6 +579,8 @@ static inline void __hlist_del(struct hl
 		next->pprev = pprev;
 }
 
+#endif
+
 static inline void hlist_del(struct hlist_node *n)
 {
 	__hlist_del(n);
@@ -592,6 +600,14 @@ static inline void hlist_del_init(struct
  * This is only for internal hlist manipulation where we know
  * the pprev/next entries already!
  */
+
+#ifdef CONFIG_DEBUG_LIST
+
+extern void __hlist_add(struct hlist_node *new,
+			struct hlist_node **pprev, struct hlist_node *next);
+
+#else
+
 static inline void __hlist_add(struct hlist_node *new,
 			struct hlist_node **pprev, struct hlist_node *next)
 {
@@ -602,6 +618,8 @@ static inline void __hlist_add(struct hl
 	new->pprev = pprev;
 }
 
+#endif
+
 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
 {
 	__hlist_add(n, &h->first, h->first);
Index: 2.6/lib/list_debug.c
===================================================================
--- 2.6.orig/lib/list_debug.c
+++ 2.6/lib/list_debug.c
@@ -54,3 +54,41 @@ void list_del(struct list_head *entry)
 	entry->prev = LIST_POISON2;
 }
 EXPORT_SYMBOL(list_del);
+
+void __hlist_del(struct hlist_node *n)
+{
+	struct hlist_node *next = n->next;
+	struct hlist_node **pprev = n->pprev;
+
+	WARN(next && next->pprev != &n->next,
+		"hlist_del corruption. next->pprev should be %p, but was %p\n",
+		&n->next, next->pprev);
+	WARN(*pprev != n,
+		"hlist_del corruption. *pprev should be %p, but was %p\n",
+		n, *pprev);
+
+	*pprev = next;
+	if (next)
+		next->pprev = pprev;
+}
+EXPORT_SYMBOL(__hlist_del);
+
+void __hlist_add(struct hlist_node *new,
+			struct hlist_node **pprev, struct hlist_node *next)
+{
+	WARN(next && next->pprev != pprev,
+		"hlist_add corruption. next->pprev should be pprev (%p), "
+		"but was %p. (next=%p).\n",
+		pprev, next->pprev, next);
+	WARN(*pprev != next,
+		"hlist_add corruption. *pprev should be next (%p), "
+		"but was %p. (pprev=%p).\n",
+		next, *pprev, pprev);
+
+	new->next = next;
+	if (next)
+		next->pprev = &new->next;
+	*pprev = new;
+	new->pprev = pprev;
+}
+EXPORT_SYMBOL(__hlist_add);