Date:   Thu, 25 Nov 2021 14:28:53 +0100
From:   Frederic Weisbecker <frederic@kernel.org>
To:     Yury Norov <yury.norov@gmail.com>
Cc:     "Paul E. McKenney" <paulmck@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Uladzislau Rezki <urezki@gmail.com>,
        Neeraj Upadhyay <quic_neeraju@quicinc.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Joel Fernandes <joel@joelfernandes.org>, rcu@vger.kernel.org,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH 5/6] rcu/nocb: Allow empty "rcu_nocbs" kernel parameter
Message-ID: <20211125132853.GA509134@lothringen>
References: <20211123003708.468409-1-frederic@kernel.org>
 <20211123003708.468409-6-frederic@kernel.org>
 <20211125004720.GV641268@paulmck-ThinkPad-P17-Gen-1>
 <20211125044132.GA105778@lapt>
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On Wed, Nov 24, 2021 at 08:41:32PM -0800, Yury Norov wrote:
> 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.  ;-)
> > 
> > I pulled this one in with the usual wordsmithing.
> > 
> > 							Thanx, Paul
> 
> I think 'rcu_nocbs=,' should work as 'none'. But I admit that it looks
> awkward. The following patch adds clear 'none' semantics to the parser.
> If you like it, I think you may drop non-documentation part of this
> patch.

I don't have real objection, but I fear that "rcu_nocbs=none" might be
interpretated as rcu_nocbs is entirely deactivated, whereas "rcu_nocbs"
alone makes it clear that we are turning something on.

We can support both though.

Thanks.