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>

1 files changed, 9 insertions, 10 deletions

diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
index e1191c996c59..5cf6731b98e9 100644
--- 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