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

[Zhiguo Niu]

Dear All,
Thanks for your discussion and suggestions , I update and send patch
version3 according to your comments.
thanks!

On Fri, Feb 2, 2024 at 10:13 AM Bart Van Assche <bvanassche@xxxxxxx> wrote:
>
> 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.