Commit 81fc685a authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds

[PATCH] lockdep: improve verbose messages

Make verbose lockdep messages (off by default) more informative by printing
out the hash chain key.  (this patch was what helped me catch the earlier
lockdep hash-collision bug)
Signed-off-by: default avatarIngo Molnar <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent a6640897
......@@ -1264,7 +1264,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
* add it and return 0 - in this case the new dependency chain is
* validated. If the key is already hashed, return 1.
static inline int lookup_chain_cache(u64 chain_key)
static inline int lookup_chain_cache(u64 chain_key, struct lock_class *class)
struct list_head *hash_head = chainhashentry(chain_key);
struct lock_chain *chain;
......@@ -1286,9 +1286,13 @@ static inline int lookup_chain_cache(u64 chain_key)
return 1;
if (very_verbose(class))
printk("\nhash chain already cached, key: %016Lx tail class: [%p] %s\n", chain_key, class->key, class->name);
return 0;
if (very_verbose(class))
printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n", chain_key, class->key, class->name);
* Allocate a new chain entry from the static array, and add
* it to the hash:
......@@ -2139,7 +2143,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
* (If lookup_chain_cache() returns with 1 it acquires
* hash_lock for us)
if (!trylock && (check == 2) && lookup_chain_cache(chain_key)) {
if (!trylock && (check == 2) && lookup_chain_cache(chain_key, class)) {
* Check whether last held lock:
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