Re: [PATCH V2] lockdep: fix deadlock issue between lockdep and rcu

[Bart Van Assche]

On 2/1/24 13:53, Boqun Feng wrote:
> Have you checked the change in the patch? Now call_rcu_zapped() has been
> splitted into two parts: preparing the callback and calling call_rcu(),
> the preparing part checks and sets the delayed_free.scheduled under
> graph_lock(), so only one CPU/thread will win and do the actual
> call_rcu(). And the RCU callback free_zapped_rcu() will unset
> delayed_free.scheduled, again under graph_lock().
>
> If you think it's still possible, could you provide a case where the
> race may happen?

Yes, I noticed that call_rcu_zapped() has been split but the first time
I took a look at this patch I wasn't sure that the new code is correct.
After having taken a second look, the new mechanism for deciding whether
or not to invoke call_rcu() seems fine to me.

Bart.