lockdep: fix mismatched lockdep_depth/curr_chain_hash

It is possible for the current->curr_chain_key to become inconsistent with the
current index if the chain fails to validate.  The end result is that future
lock_acquire() operations may inadvertently fail to find a hit in the cache
resulting in a new node being added to the graph for every acquire.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 5 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 734da579ad13..42ae4a5ab4dc 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1521,7 +1521,7 @@ cache_hit:
 }
 
 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
-                struct held_lock *hlock, int chain_head)
+                struct held_lock *hlock, int chain_head, u64 chain_key)
 {
         /*
          * Trylock needs to maintain the stack of held locks, but it
@@ -1534,7 +1534,7 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
          * graph_lock for us)
          */
         if (!hlock->trylock && (hlock->check == 2) &&
-                        lookup_chain_cache(curr->curr_chain_key, hlock->class)) {
+                        lookup_chain_cache(chain_key, hlock->class)) {
                 /*
                  * Check whether last held lock:
                  *
@@ -1576,7 +1576,7 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
 #else
 static inline int validate_chain(struct task_struct *curr,
                 struct lockdep_map *lock, struct held_lock *hlock,
-                int chain_head)
+                int chain_head, u64 chain_key)
 {
         return 1;
 }
@@ -2450,11 +2450,11 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                 chain_head = 1;
         }
         chain_key = iterate_chain_key(chain_key, id);
-        curr->curr_chain_key = chain_key;
 
-        if (!validate_chain(curr, lock, hlock, chain_head))
+        if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
                 return 0;
 
+        curr->curr_chain_key = chain_key;
         curr->lockdep_depth++;
         check_chain_key(curr);
 #ifdef CONFIG_DEBUG_LOCKDEP