linux-kernel - Re: [PATCH] sched/isolation: reconcile rcu_nocbs= and nohz

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Message-ID: <YJ4e2j+FewuJ4zdZ@gmail.com>
Date:   Fri, 14 May 2021 08:55:22 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Paul Gortmaker <paul.gortmaker@...driver.com>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH] sched/isolation: reconcile rcu_nocbs= and nohz_full=


* Paul E. McKenney <paulmck@...nel.org> wrote:

> On Thu, May 13, 2021 at 02:13:28PM +0200, Ingo Molnar wrote:
> > 
> > * Paul E. McKenney <paulmck@...nel.org> 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@...nel.org>
> > 
> > Thanks - added this fix to tip:sched/core.
> 
> Very good, I will drop it from -rcu later today, Pacific Time.

Thank you!

	Ingo