Message-ID: <4B544571.7020609@kernel.org>
Date: Mon, 18 Jan 2010 20:26:41 +0900
From: Tejun Heo <tj@kernel.org>
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To: Peter Zijlstra <peterz@infradead.org>
CC: torvalds@linux-foundation.org, mingo@elte.hu, awalls@radix.net,
       linux-kernel@vger.kernel.org, jeff@garzik.org,
       akpm@linux-foundation.org, jens.axboe@oracle.com, rusty@rustcorp.com.au,
       cl@linux-foundation.org, dhowells@redhat.com, arjan@linux.intel.com,
       avi@redhat.com, johannes@sipsolutions.net, andi@firstfloor.org
Subject: Re: [PATCH 01/40] sched: consult online mask instead of active in
 select_fallback_rq()
References: <1263776272-382-1-git-send-email-tj@kernel.org>	 <1263776272-382-2-git-send-email-tj@kernel.org> <1263809620.4283.173.camel@laptop>
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Hello,

On 01/18/2010 07:13 PM, Peter Zijlstra wrote:
> On Mon, 2010-01-18 at 09:57 +0900, Tejun Heo wrote:
>> If called after sched_class chooses a CPU which isn't in a task's
>> cpus_allowed mask,
> 
> I can only see this happening when you're changing cpus_allowed after
> starting to take down the cpu. IOW you're moving a thread to a dying
> cpu.
> 
> This is because you're spawning workqueue threads while we're going
> down?

It got triggered by the hotplug callback creating the trustee kthread
and kthread_bind()ing it to the target cpu during CPU_DOWN_PREPARE.

Thanks.

-- 
tejun
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