locking: Add WARN_ON_ONCE lock assertion

commit 9a37110d upstream.

An interface may need to assert a lock invariant and not flood the
system logs; add a lockdep helper macro equivalent to
lockdep_assert_held() which only WARNs once.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

include/linux/lockdep.h

@@ -342,6 +342,9 @@ extern void lockdep_trace_alloc(gfp_t mask);
 #define lockdep_depth(tsk)	(debug_locks ? (tsk)->lockdep_depth : 0)
 
 #define lockdep_assert_held(l)	WARN_ON(debug_locks && !lockdep_is_held(l))
+#define lockdep_assert_held_once(l)	do {				\
+		WARN_ON_ONCE(debug_locks && !lockdep_is_held(l));	\
+	} while (0)
 
 #else /* !LOCKDEP */
 
@@ -362,6 +365,7 @@ static inline void lockdep_on(void)
 # define lockdep_trace_alloc(g)			do { } while (0)
 # define lockdep_init()				do { } while (0)
 # define lockdep_info()				do { } while (0)
+
 # define lockdep_init_map(lock, name, key, sub) \
 		do { (void)(name); (void)(key); } while (0)
 # define lockdep_set_class(lock, key)		do { (void)(key); } while (0)
@@ -391,6 +395,7 @@ struct lock_class_key { };
 #define lockdep_depth(tsk)	(0)
 
 #define lockdep_assert_held(l)			do { } while (0)
+#define lockdep_assert_held_once(l)		do { (void)(l); } while (0)
 
 #endif /* !LOCKDEP */