list debugging: warn when deleting a deleted entry

Use the magic LIST_POISON* values to detect an incorrect use of list_del on a deleted entry. This DEBUG_LIST specific warning is easier to understand than the generic Oops message caused by LIST_POISON dereference. Signed-off-by: Baruch Siach <[email protected]> Cc: Dave Jones <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
mna · Aug 10, 2010 · e3f76e3 · e3f76e3
1 parent 55817d3
commit e3f76e3
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/lib/list_debug.c b/lib/list_debug.c
@@ -43,6 +43,12 @@ EXPORT_SYMBOL(__list_add);
  */
 void list_del(struct list_head *entry)
 {
+	WARN(entry->next == LIST_POISON1,
+		"list_del corruption, next is LIST_POISON1 (%p)\n",
+		LIST_POISON1);
+	WARN(entry->next != LIST_POISON1 && entry->prev == LIST_POISON2,
+		"list_del corruption, prev is LIST_POISON2 (%p)\n",
+		LIST_POISON2);
 	WARN(entry->prev->next != entry,
 		"list_del corruption. prev->next should be %p, "
 		"but was %p\n", entry, entry->prev->next);