Re: [RFC] Deadlock via recursive wakeup via RCU with threadirqs

From: Joel Fernandes
Date: Thu Jun 27 2019 - 11:42:34 EST

On Thu, Jun 27, 2019 at 11:40 AM Sebastian Andrzej Siewior
<bigeasy@xxxxxxxxxxxxx> wrote:
> On 2019-06-27 11:37:10 [-0400], Joel Fernandes wrote:
> > Sebastian it would be nice if possible to trace where the
> > t->rcu_read_unlock_special is set for this scenario of calling
> > rcu_read_unlock_special, to give a clear idea about whether it was
> > really because of an IPI. I guess we could also add additional RCU
> > debug fields to task_struct (just for debugging) to see where there
> > unlock_special is set.
> >
> > Is there a test to reproduce this, or do I just boot an intel x86_64
> > machine with "threadirqs" and run into it?
> Do you want to send me a patch or should I send you my kvm image which
> triggers the bug on boot?

I think the kvm image would be better so I reproduce it on my side.
After that I can share any debug patches with you if they are useful.