linux-kernel - Re: [RFD PATCH 3/5] sched/cpufreq_schedutil: make worker kthread be SCHED

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Date:   Thu, 30 Mar 2017 22:22:24 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Vikram Mulukutla <markivx@...eaurora.org>,
        Mark Brown <broonie@...nel.org>
Cc:     Juri Lelli <juri.lelli@....com>,
        Peter Zijlstra <peterz@...radead.org>, mingo@...hat.com,
        viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, tglx@...utronix.de,
        vincent.guittot@...aro.org, rostedt@...dmis.org,
        luca.abeni@...tannapisa.it, claudio@...dence.eu.com,
        tommaso.cucinotta@...tannapisa.it, bristot@...hat.com,
        mathieu.poirier@...aro.org, tkjos@...roid.com, joelaf@...gle.com,
        andresoportus@...gle.com, morten.rasmussen@....com,
        dietmar.eggemann@....com, patrick.bellasi@....com,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel-owner@...r.kernel.org
Subject: Re: [RFD PATCH 3/5] sched/cpufreq_schedutil: make worker kthread be SCHED_DEADLINE

On Thursday, March 30, 2017 08:50:11 AM Vikram Mulukutla wrote:
> 
> > OK
> > 
> > So there are two pieces here.
> > 
> > One is that if we want *all* drivers to work with schedutil, we need to 
> > keep
> > the kthread for the ones that will never be reworked (because nobody 
> > cares
> > etc).  But then perhaps the kthread implementation may be left alone 
> > (because
> > nobody cares etc).
> > 
> > The second one is that there are drivers operating in-context that work 
> > with
> > schedutil already, so I don't see major obstacles to making more 
> > drivers work
> > that way.  That would be only a matter of reworking the drivers in 
> > question.
> > 
> > Thanks,
> > Rafael
> 
> There are some MSM platforms that do need a kthread and would love to 
> use
> schedutil. This is all mainly due to the point that Vincent raised; 
> having
> to actually wait for voltage transitions before clock switches. I can't
> speak about the future, but that's the situation right now. Leaving the
> kthread alone for now would be appreciated!

I was not arguing for removing the kthread (quite opposite rather).

My point was that *if* it is viable to rework drivers to operate in-context,
that would be the way to go IMO instead of messing up with the kthread thing.

Thanks,
Rafael