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>

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 734da579ad134779685cbf0291fbc6e14e9cc133..42ae4a5ab4dce0b1c38bc4edc2530ca7ca3448d6 100644 (file)
--- 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