lockdep: fix mismatched lockdep_depth/curr_chain_hash

patch 3aa416b07f0adf01c090baab26fb70c35ec17623 in mainline.

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.

[ peterz: this might explain some of the lockdep is so _slow_ complaints. ]
[ mingo: this does not impact the correctness of validation, but may slow
  down future operations significantly, if the chain gets very long. ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 1a5ff2211d8898076c601d4f9c639bfe34f5927c..072cf2533251b9520707f19e957ae1ad05edebd5 100644 (file)
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2166,7 +2166,6 @@ out_calc_hash:
        }
 #endif
        chain_key = iterate_chain_key(chain_key, id);
-       curr->curr_chain_key = chain_key;
 
        /*
         * Trylock needs to maintain the stack of held locks, but it
@@ -2215,6 +2214,7 @@ out_calc_hash:
                if (unlikely(!debug_locks))
                        return 0;
 
+       curr->curr_chain_key = chain_key;
        curr->lockdep_depth++;
        check_chain_key(curr);
 #ifdef CONFIG_DEBUG_LOCKDEP