linux-kernel - Re: [PATCH 06/16] sched: SCHED

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Date:	Thu, 12 Apr 2012 20:28:24 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Juri Lelli <juri.lelli@...il.com>, peterz@...radead.org,
	tglx@...utronix.de, mingo@...hat.com, cfriesen@...tel.com,
	oleg@...hat.com, fweisbec@...il.com, darren@...art.com,
	johan.eker@...csson.com, p.faure@...tech.ch,
	linux-kernel@...r.kernel.org, claudio@...dence.eu.com,
	michael@...rulasolutions.com, fcheccon@...per.es
Subject: Re: [PATCH 06/16] sched: SCHED_DEADLINE push and pull logic

On Wed, Apr 11, 2012 at 10:10 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Fri, 2012-04-06 at 21:39 +0800, Hillf Danton wrote:
>
>> > +static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
>> > +{
>> > +       dl_rq = &rq_of_dl_rq(dl_rq)->dl;
>> > +
>> > +       dl_rq->dl_nr_total++;
>> > +       if (dl_se->nr_cpus_allowed > 1)
>> > +               dl_rq->dl_nr_migratory++;
>> > +
>> > +       update_dl_migration(dl_rq);
>>
>>       if (dl_se->nr_cpus_allowed > 1) {
>>               dl_rq->dl_nr_migratory++;
>>               /* No change in migratory, no update of migration */
>
> This is not true. As dl_nr_total changed. If there was only one dl task
> queued that can migrate, and then another dl task is queued but this
> task can not migrate, the update_dl_migration still needs to be called.
> As dl_nr_migratory would be 1, but now dl_nr_total > 1. This means we
> are now overloaded.
>
	if (2 == dl_nr_migratory + dl_nr_total)
		rq was not overloaded;

	after enqueuing a deadline task that is not migratory,

	if (current task is not preempted)
		rq remains not overloaded;

	else if (current task is not pushed out) {
		if (rq is not overloaded)
			maintenance of overloaded is __corrupted__;
	}

btw, same behavior in RTS?
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