Re: WARNING: suspicious RCU usage - while installing a VM on a CPU listed under nohz_full

[Wanpeng Li]

On Tue, 28 Jul 2020 at 22:40, Nitesh Narayan Lal <nitesh@xxxxxxxxxx> wrote:
>
> Hi,
>
> I have recently come across an RCU trace with the 5.8-rc7 kernel that has the
> debug configs enabled while installing a VM on a CPU that is listed under
> nohz_full.
>
> Based on some of the initial debugging, my impression is that the issue is
> triggered because of the fastpath that is meant to optimize the writes to x2APIC
> ICR that eventually leads to a virtual IPI in fixed delivery mode, is getting
> invoked from the quiescent state.

I still can reproduce this after removing the ipi/timer fastpath
codes, anyway, I will have a look.