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SubjectRe: [PATCH] locking/lockdep: Avoid potential access of invalid memory in lock_class
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On 1/3/22 12:47, Bart Van Assche wrote:
> On 1/2/22 18:35, Waiman Long wrote:
>> -    WARN_ON_ONCE(!found);
>> -    __lockdep_free_key_range(pf, key, 1);
>> -    call_rcu_zapped(pf);
>> -    graph_unlock();
>> -out_irq:
>> +    WARN_ON_ONCE(!found && debug_locks);
>
> lockdep_unregister_key() should only be called for a registered key so
> I'd
> like to keep the WARN_ON_ONCE(!found) here instead of changing it into
> WARN_ON_ONCE(!found && debug_locks). Otherwise this patch looks good
> to me.

The reason for this change is to handle the case that a
lockdep_register_key()/lockdep_unregister_key() pair may be called after
debug_locks is turned off. Without that change, we are going to get the
warning in lockdep_unregister_key(). That is the motivation of your
original commit 8b39adbee805 ("locking/lockdep: Make
lockdep_unregister_key() honor 'debug_locks' again").

Cheers,
Longman


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