linux-kernel - Re: [PATCH]: exec: avoid propagating PF_NO

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Message-ID: <20131128121748.GN10022@twins.programming.kicks-ass.net>
Date:	Thu, 28 Nov 2013 13:17:48 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Tejun Heo <htejun@...il.com>, zhang.yi20@....com.cn,
	lkml <linux-kernel@...r.kernel.org>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH]: exec: avoid propagating PF_NO_SETAFFINITY into
 userspace child

On Thu, Nov 28, 2013 at 12:45:42PM +0100, Oleg Nesterov wrote:
> It has? khelper is a workqueue thread, this flag is set by create_worker().
> 
> And it does kernel_thread() (not kthread_create()) so the child gets this
> flag too.

Urgh, but that's still completely wrong. khelper is a singlethread
workqueue, those should be unbound and therefore should not have this
flag set at all.

In fact, I know people want to set affinity on khelper to ensure all the
usermode helper tasks get spawned on the specific system-cpus and leave
the rest of the system unperturbed.

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