linux-kernel - Re: [PATCH repost] sched: export sched

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Message-ID: <1277984603.1917.15.camel@laptop>
Date:	Thu, 01 Jul 2010 13:43:23 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Sridhar Samudrala <sri@...ibm.com>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	netdev <netdev@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitri Vorobiev <dmitri.vorobiev@...ial.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH repost] sched: export sched_set/getaffinity to modules

On Thu, 2010-07-01 at 13:19 +0200, Peter Zijlstra wrote:
> On Thu, 2010-07-01 at 14:07 +0300, Michael S. Tsirkin wrote:
> > Author: Sridhar Samudrala <sri@...ibm.com>
> > 
> > sched: export sched_set/getaffinity to modules
> > 
> > vhost-net driver wants to copy the affinity from the
> > owner thread to thread it creates. Export
> > sched_set/get affinity to modules to make this possible
> > when vhost is built as a module.

> Urgh,.. so why again is that a good idea?

In particular:
 - who sets the affinity of the task? 
 - why can't it set the kernel thread's affinity too?
 - what happens if someone changes the tasks' affinity?

So no, I don't think this is a sensible thing to do at all.
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