linux-kernel - Re: [PATCH 5/6] rcu/nocb: Allow empty "rcu

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Message-ID: <20211125005526.GA490855@lothringen>
Date:   Thu, 25 Nov 2021 01:55:26 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org,
        yury.norov@...il.com
Subject: Re: [PATCH 5/6] rcu/nocb: Allow empty "rcu_nocbs" kernel parameter

On Wed, Nov 24, 2021 at 04:47:20PM -0800, Paul E. McKenney wrote:
> On Tue, Nov 23, 2021 at 01:37:07AM +0100, Frederic Weisbecker wrote:
> > If a user wants to boot without any CPU in offloaded mode initially but
> > with the possibility to offload them later using cpusets, provide a way
> > to simply pass an empty "rcu_nocbs" kernel parameter which will enforce
> > the creation of dormant nocb kthreads.
> 
> Huh.  This would have been a use for Yury Norov's "none" bitmask
> specifier.  ;-)

This must be the last missing piece before we can finally support NR_CPUS=0 ;)

> 
> I pulled this one in with the usual wordsmithing.

Thanks!