locking/mutex: Fix debug_mutexes

debug_mutex_unlock() would bail when !debug_locks and forgets to
actually unlock.

Reported-by: "Michael L. Semon" <mlsemon35@gmail.com>
Reported-by: "Kirill A. Shutemov" <kirill@shutemov.name>
Reported-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Fixes: 6f008e72cd11 ("locking/mutex: Fix debug checks")
Tested-by: Dave Jones <davej@redhat.com>
Cc: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140410141559.GE13658@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
index e1191c9..5cf6731 100644 (file)
--- a/kernel/locking/mutex-debug.c
+++ b/kernel/locking/mutex-debug.c
@@ -71,18 +71,17 @@ void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
 
 void debug_mutex_unlock(struct mutex *lock)
 {
-       if (unlikely(!debug_locks))
-               return;
+       if (likely(debug_locks)) {
+               DEBUG_LOCKS_WARN_ON(lock->magic != lock);
 
-       DEBUG_LOCKS_WARN_ON(lock->magic != lock);
+               if (!lock->owner)
+                       DEBUG_LOCKS_WARN_ON(!lock->owner);
+               else
+                       DEBUG_LOCKS_WARN_ON(lock->owner != current);
 
-       if (!lock->owner)
-               DEBUG_LOCKS_WARN_ON(!lock->owner);
-       else
-               DEBUG_LOCKS_WARN_ON(lock->owner != current);
-
-       DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
-       mutex_clear_owner(lock);
+               DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
+               mutex_clear_owner(lock);
+       }
 
        /*
         * __mutex_slowpath_needs_to_unlock() is explicitly 0 for debug