linux-kernel - Re: [PATCH v8 05/16] sched/core: Allow sched

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Date:   Thu, 9 May 2019 13:55:17 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v8 05/16] sched/core: Allow sched_setattr() to use the
 current policy

On Thu, May 09, 2019 at 10:18:07AM +0100, Patrick Bellasi wrote:
> On 08-May 21:21, Peter Zijlstra wrote:
> > On Tue, Apr 02, 2019 at 11:41:41AM +0100, Patrick Bellasi wrote:
> > > diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
> > > index 22627f80063e..075c610adf45 100644
> > > --- a/include/uapi/linux/sched.h
> > > +++ b/include/uapi/linux/sched.h
> > > @@ -40,6 +40,8 @@
> > >  /* SCHED_ISO: reserved but not implemented yet */
> > >  #define SCHED_IDLE		5
> > >  #define SCHED_DEADLINE		6
> > > +/* Must be the last entry: used to sanity check attr.policy values */
> > > +#define SCHED_POLICY_MAX	SCHED_DEADLINE
> > 
> > This is a wee bit sad to put in a uapi header; but yeah, where else :/
> > 
> > Another option would be something like:
> > 
> > enum {
> > 	SCHED_NORMAL = 0,
> > 	SCHED_FIFO = 1,
> > 	SCHED_RR = 2,
> > 	SCHED_BATCH = 3,
> > 	/* SCHED_ISO = 4, reserved */
> > 	SCHED_IDLE = 5,
> > 	SCHED_DEADLINE = 6,
> > 	SCHED_POLICY_NR
> > };
> 
> I just wanted to minimize the changes by keeping the same structure...
> If you prefer the above I can add a refactoring patch just to update
> existing definitions before adding this patch...

Right; I've no idea really. The thing that started all this was adding
that define to UAPI. Maybe we can do without it and instead put in a
comment to check sched_setattr() any time we add a new policy and just
hard code the thing.