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Subject: Re: [patch] Re: autogroup: sched_setscheduler() fails
From: Mike Galbraith <efault@gmx.de>
To: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, bharata@linux.vnet.ibm.com,
        Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
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Date: Wed, 12 Jan 2011 07:25:26 +0100
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On Wed, 2011-01-12 at 13:43 +0800, Yong Zhang wrote:
> On Tue, Jan 11, 2011 at 12:42 AM, Mike Galbraith <efault@gmx.de> wrote:
> > Index: linux-2.6/kernel/sched_autogroup.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/sched_autogroup.c
> > +++ linux-2.6/kernel/sched_autogroup.c
> > @@ -73,6 +73,15 @@ static inline struct autogroup *autogrou
> >        ag->id = atomic_inc_return(&autogroup_seq_nr);
> >        ag->tg = tg;
> >        tg->autogroup = ag;
> > +#ifdef CONFIG_RT_GROUP_SCHED
> > +       /*
> > +        * HACK: autogroup RT tasks run in the root task group.
> > +        * This fools __sched_setscheduler() into proceeding on
> > +        * so we can move the task to the appropriate runqueue
> > +        * upon scheduling policy change.
> > +        */
> > +       tg->rt_bandwidth.rt_runtime = RUNTIME_INF;
> > +#endif
> >
> >        return ag;
> >
> > @@ -143,6 +152,15 @@ autogroup_move_group(struct task_struct
> >        autogroup_kref_put(prev);
> >  }
> >
> > +static inline void
> > +autogroup_setscheduler(struct task_struct *p, int on_rq)
> > +{
> > +       if (p->sched_class->task_move_group)
> > +               p->sched_class->task_move_group(p, on_rq);
> 
> This will be called even if we don't change the sched_class in
> which case it is not necessary.

Yes.  It'll also piddle around with tasks it shouldn't.  I sent what I
hope is a better solution a few minutes ago.  This one works, but
probably upset Peter's tummy mightily :)

	-Mike