linux-kernel - Re: [PATCH 2/4] sched: adjust when cpu_active and cpuset configurations are updated during cpu on/offlining

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Message-ID: <4C053C39.9070405@kernel.org>
Date:	Tue, 01 Jun 2010 18:58:33 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	mingo@...e.hu, linux-kernel@...r.kernel.org, rusty@...tcorp.com.au,
	paulus@...ba.org, acme@...hat.com, Paul Menage <menage@...gle.com>
Subject: Re: [PATCH 2/4] sched: adjust when cpu_active and cpuset configurations
 are updated during cpu on/offlining

Hello,

On 06/01/2010 05:57 PM, Peter Zijlstra wrote:
> I know we all love notifier lists, but doesn't the below code get lots
> more readable if we don't play tricks with notifier priorities and
> simply hardcode the few (perf/sched/cpuset) callbacks into the hotplug
> paths?

Maybe, maybe not.  In this case, I kind of like that sleep failure
case doesn't have to be explicitly rolled back but if you like hard
coding that's fine too.

> Also, I'm afraid you've now inverted the relation between
> cpu_active_mask and parition_sched_domains().
>
> You need to first set/clear the active mask, then rebuild the domain.
> But with your patch parition_sched_domains() gets called in the regular
> DOWN_PREPARE path, while we only clear active at the very end, which
> means we build the wrong domains.

Ah, right forgot about that.  So, the things that need to be ordered
are cpu_active mask update, cpuset configuration and sched domains,
right?

Thanks.

-- 
tejun
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