From: Jarek Poplawski <jarkao2@o2.pl>

In __lock_acquire check_chain_key can turn off debug_locks, so check is
needed to assure proper return code.

Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/lockdep.c |    4 ++++
 1 file changed, 4 insertions(+)

diff -puN kernel/lockdep.c~lockdep-debug_locks-check-after-check_chain_key kernel/lockdep.c
--- a/kernel/lockdep.c~lockdep-debug_locks-check-after-check_chain_key
+++ a/kernel/lockdep.c
@@ -2227,6 +2227,10 @@ out_calc_hash:
 
 	curr->lockdep_depth++;
 	check_chain_key(curr);
+#ifdef CONFIG_DEBUG_LOCKDEP
+	if (unlikely(!debug_locks))
+		return 0;
+#endif
 	if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
 		debug_locks_off();
 		printk("BUG: MAX_LOCK_DEPTH too low!\n");
_