locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache

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.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20190214230058.196511-5-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 1 insertions, 10 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index ec6f6aff4d8d..21d84510e28f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2195,16 +2195,8 @@ 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;
 
@@ -2212,7 +2204,6 @@ 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);