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Date: Thu, 11 Nov 2010 16:27:51 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Raistlin <raistlin@...ux.it>, Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
Steven Rostedt <rostedt@...dmis.org>,
Chris Friesen <cfriesen@...tel.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Darren Hart <darren@...art.com>,
Johan Eker <johan.eker@...csson.com>,
"p.faure" <p.faure@...tech.ch>,
linux-kernel <linux-kernel@...r.kernel.org>,
Claudio Scordino <claudio@...dence.eu.com>,
michael trimarchi <trimarchi@...is.sssup.it>,
Fabio Checconi <fabio@...dalf.sssup.it>,
Tommaso Cucinotta <cucinotta@...up.it>,
Juri Lelli <juri.lelli@...il.com>,
Nicola Manica <nicola.manica@...i.unitn.it>,
Luca Abeni <luca.abeni@...tn.it>,
Dhaval Giani <dhaval@...is.sssup.it>,
Harald Gustafsson <hgu1972@...il.com>,
paulmck <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 06/22] sched: SCHED_DEADLINE handles spacial
kthreads
On 11/11, Peter Zijlstra wrote:
>
> On Fri, 2010-10-29 at 08:31 +0200, Raistlin wrote:
> > @@ -6071,7 +6104,7 @@ void sched_idle_next(void)
> > */
> > raw_spin_lock_irqsave(&rq->lock, flags);
> >
> > - __setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);
> > + __setscheduler_dl_special(rq, p);
> >
> > activate_task(rq, p, 0);
> >
>
> Ingo, happen to know if this is really needed these days? hotplug should
> have migrated all other tasks away, leaving only the idle task to run.
This is called before CPU_DEAD stage which migrates all tasks away.
Sorry, can't resist, off-topic quiestion. Do we really need
migration_call()->migrate_live_tasks() ?
With the recent changes, try_to_wake_up() can never choose
the dead (!cpu_online) cpu if the task was deactivated.
Looks like we should only worry about the running tasks, and
migrate_dead_tasks()->pick_next_task() loop seems to all work
we need.
(Of course, we can't just remove migrate_live_tasks(), at leat
migrate_dead() needs simple changes).
What do you think?
Oleg.
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