Re: [PATCH 3/6] dataplane nohz: run softirqs synchronously on user entry

Paul E. McKenney
2015-05-12T13:08:32Z

On Tue, May 12, 2015 at 11:32:02AM +0200, Peter Zijlstra wrote:
> On Mon, May 11, 2015 at 04:13:16PM -0400, Chris Metcalf wrote:
> > The thing you want to avoid is having two processes both
> > runnable at once
>
> Right, because as soon as nr_running > 1 we kill the entire nohz_full
> thing. RT or not for ksoftirqd doesn't matter.
>
> Then again, like interrupts, you basically want to avoid softirqs in
> this mode.
>
> So I think the right solution is to figure out why the softirqs get
> raised and cure that.

Makes sense, but it also makes sense to have something that detects
when that cure fails and clean up. And, in a test/debug environment,
also issuing some sort of diagnostic in that case.

Thanx, Paul