Re: [PATCH] sched/isolation: reconcile rcu_nocbs= and nohz_full=

From: Paul E. McKenney
Date: Thu May 13 2021 - 10:22:31 EST


On Thu, May 13, 2021 at 02:13:28PM +0200, Ingo Molnar wrote:
>
> * Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
>
> > On Mon, Apr 19, 2021 at 12:26:59AM -0400, Paul Gortmaker wrote:
> > > We have a mismatch between RCU and isolation -- in relation to what is
> > > considered the maximum valid CPU number.
> > >
> > > This matters because nohz_full= and rcu_nocbs= are joined at the hip; in
> > > fact the former will enforce the latter. So we don't want a CPU mask to
> > > be valid for one and denied for the other.
> > >
> > > The difference 1st appeared as of v4.15; further details are below.
> >
> > I pulled this into -rcu for testing and further review.
> >
> > If it should instead go through some other tree:
> >
> > Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>
> Thanks - added this fix to tip:sched/core.

Very good, I will drop it from -rcu later today, Pacific Time.

Thanx, Paul