list.h: add list_is_singular()
Add list_is_singular() to check a list has just one entry.
list_is_singular() is useful to check whether a list_head which have been
temporarily allocated for listing objects can be released or not.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/list.h b/include/linux/list.h
index dac16f9..b4a939b 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -319,6 +319,15 @@
return (next == head) && (next == head->prev);
}
+/**
+ * list_is_singular - tests whether a list has just one entry.
+ * @head: the list to test.
+ */
+static inline int list_is_singular(const struct list_head *head)
+{
+ return !list_empty(head) && (head->next == head->prev);
+}
+
static inline void __list_splice(struct list_head *list,
struct list_head *head)
{