1 files changed, 29 insertions, 12 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2168e94715b9..6c97f67ec321 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3808,7 +3808,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                                 hlock->references = 2;
                         }
 
-                        return 1;
+                        return 2;
                 }
         }
 
@@ -4011,22 +4011,33 @@ out:
 }
 
 static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
-                              int idx)
+                                int idx, unsigned int *merged)
 {
         struct held_lock *hlock;
+        int first_idx = idx;
 
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return 0;
 
         for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
-                if (!__lock_acquire(hlock->instance,
+                switch (__lock_acquire(hlock->instance,
                                     hlock_class(hlock)->subclass,
                                     hlock->trylock,
                                     hlock->read, hlock->check,
                                     hlock->hardirqs_off,
                                     hlock->nest_lock, hlock->acquire_ip,
-                                    hlock->references, hlock->pin_count))
+                                    hlock->references, hlock->pin_count)) {
+                case 0:
                         return 1;
+                case 1:
+                        break;
+                case 2:
+                        *merged += (idx == first_idx);
+                        break;
+                default:
+                        WARN_ON(1);
+                        return 0;
+                }
         }
         return 0;
 }
@@ -4037,9 +4048,9 @@ __lock_set_class(struct lockdep_map *lock, const char *name,
                  unsigned long ip)
 {
         struct task_struct *curr = current;
+        unsigned int depth, merged = 0;
         struct held_lock *hlock;
         struct lock_class *class;
-        unsigned int depth;
         int i;
 
         if (unlikely(!debug_locks))
@@ -4066,14 +4077,14 @@ __lock_set_class(struct lockdep_map *lock, const char *name,
         curr->lockdep_depth = i;
         curr->curr_chain_key = hlock->prev_chain_key;
 
-        if (reacquire_held_locks(curr, depth, i))
+        if (reacquire_held_locks(curr, depth, i, &merged))
                 return 0;
 
         /*
          * I took it apart and put it back together again, except now I have
          * these 'spare' parts.. where shall I put them.
          */
-        if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
+        if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
                 return 0;
         return 1;
 }
@@ -4081,8 +4092,8 @@ __lock_set_class(struct lockdep_map *lock, const char *name,
 static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
 {
         struct task_struct *curr = current;
+        unsigned int depth, merged = 0;
         struct held_lock *hlock;
-        unsigned int depth;
         int i;
 
         if (unlikely(!debug_locks))
@@ -4109,7 +4120,11 @@ static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
         hlock->read = 1;
         hlock->acquire_ip = ip;
 
-        if (reacquire_held_locks(curr, depth, i))
+        if (reacquire_held_locks(curr, depth, i, &merged))
+                return 0;
+
+        /* Merging can't happen with unchanged classes.. */
+        if (DEBUG_LOCKS_WARN_ON(merged))
                 return 0;
 
         /*
@@ -4118,6 +4133,7 @@ static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
          */
         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
                 return 0;
+
         return 1;
 }
 
@@ -4132,8 +4148,8 @@ static int
 __lock_release(struct lockdep_map *lock, unsigned long ip)
 {
         struct task_struct *curr = current;
+        unsigned int depth, merged = 1;
         struct held_lock *hlock;
-        unsigned int depth;
         int i;
 
         if (unlikely(!debug_locks))
@@ -4192,14 +4208,15 @@ __lock_release(struct lockdep_map *lock, unsigned long ip)
         if (i == depth-1)
                 return 1;
 
-        if (reacquire_held_locks(curr, depth, i + 1))
+        if (reacquire_held_locks(curr, depth, i + 1, &merged))
                 return 0;
 
         /*
          * We had N bottles of beer on the wall, we drank one, but now
          * there's not N-1 bottles of beer left on the wall...
+         * Pouring two of the bottles together is acceptable.
          */
-        DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth-1);
+        DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
 
         /*
          * Since reacquire_held_locks() would have called check_chain_key()