[PATCH v6 02/16] locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache

[Bart Van Assche]

Make sure that add_chain_cache() returns 0 and does not modify the
chain hash if nr_chain_hlocks == MAX_LOCKDEP_CHAIN_HLOCKS before this
function is called.

Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Waiman Long <long...@redhat.com>
Cc: Johannes Berg <johan...@sipsolutions.net>
Signed-off-by: Bart Van Assche <bvanass...@acm.org>
---
 kernel/locking/lockdep.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index cb3fa7042886..7a7c2d7b01c2 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2206,16 +2206,8 @@ static inline int add_chain_cache(struct task_struct 
*curr,
                        chain_hlocks[chain->base + j] = lock_id;
                }
                chain_hlocks[chain->base + j] = class - lock_classes;
-       }
-
-       if (nr_chain_hlocks < MAX_LOCKDEP_CHAIN_HLOCKS)
                nr_chain_hlocks += chain->depth;
-
-#ifdef CONFIG_DEBUG_LOCKDEP
-       /*
-        * Important for check_no_collision().
-        */
-       if (unlikely(nr_chain_hlocks > MAX_LOCKDEP_CHAIN_HLOCKS)) {
+       } else {
                if (!debug_locks_off_graph_unlock())
                        return 0;
 
@@ -2223,7 +2215,6 @@ static inline int add_chain_cache(struct task_struct 
*curr,
                dump_stack();
                return 0;
        }
-#endif
 
        hlist_add_head_rcu(&chain->entry, hash_head);
        debug_atomic_inc(chain_lookup_misses);
-- 
2.20.1.97.g81188d93c3-goog