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Subject[PATCH v6 02/16] locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache
Date
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 <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Bart Van Assche <bvanassche@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
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