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Subject: Re: [RFC 0/12][PATCH] SCHED_DEADLINE: fork and terminate task logic
From: Dario Faggioli <faggioli@gandalf.sssup.it>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
       michael trimarchi <michael@evidence.eu.com>,
       Fabio Checconi <fabio@gandalf.sssup.it>, Ingo Molnar <mingo@elte.hu>,
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On Wed, 2010-01-13 at 17:15 +0100, Peter Zijlstra wrote:
> On Wed, 2010-01-13 at 12:11 +0100, Raistlin wrote:
>=20
> > > > +       } else if (rt_prio(p->prio))
> > > > +               p->sched_class =3D &rt_sched_class;
> > > > +       else
> > > >                 p->sched_class =3D &fair_sched_class;
> > > > =20
> > > >  #ifdef CONFIG_SMP
> > > > @@ -2744,6 +2756,10 @@ static void finish_task_switch(struct rq *rq=
, struct task_struct *prev)
> > > >         if (mm)
> > > >                 mmdrop(mm);
> > > >         if (unlikely(prev_state =3D=3D TASK_DEAD)) {
> > > > +               /* a deadline task is dying: stop the bandwidth tim=
er */
> > > > +               if (deadline_task(prev))
> > > > +                       hrtimer_cancel(&prev->dl.dl_timer);
> > > > +
> > > >                 /*
> > > >                  * Remove function-return probe instances associate=
d with this
> > > >                  * task and put them back on the free list.=20
> > >=20
> > > Shouldn't this be done in the ->dequeue_task() callback?
> > >
> > Not sure of this snippet... Actually, it is one of the most disturbing
> > piece of code of this whole scheduler. :-(
> >=20
> > The reason why it is here is that I think it is needed to call
> > hrtimer_cancel() _without_ holding the rq->lock, is that correct?
>=20
> I think we can nest the hrtimer base lock inside the rq->lock these
> days, so it should be safe to call while holding it, anyway, lockdep
> will quickly tell you if you try ;-)
>=20
Nice, I'll try this soon, thanks.

> > It is=20
>=20
> Is that a stmt or an unfinished sentence?
>=20
No, this is nothing, sorry! :-P

Regards,
Dario


--=20
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

http://blog.linux.it/raistlin / raistlin@ekiga.net /
dario.faggioli@jabber.org

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