linux-kernel - Re: kmod: avoid propagating PF_NO_SETAFFINITY into userspace child

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Message-ID: <20131114052326.GA29031@mtj.dyndns.org>
Date:	Thu, 14 Nov 2013 14:23:26 +0900
From:	Tejun Heo <tj@...nel.org>
To:	zhang.yi20@....com.cn
Cc:	linux-kernel@...r.kernel.org,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: kmod: avoid propagating PF_NO_SETAFFINITY into userspace child

Hello,

On Thu, Nov 14, 2013 at 09:51:47AM +0800, zhang.yi20@....com.cn wrote:
> The kernel worker thread has the PF_NO_SETAFFINITY flag, and it is propagated
> into the userspace child. Clearing this flag in usersapce child to enable its
> migrating capability.
> 
> 
> Signed-off-by: Zhang Yi <zhang.yi20@....com.cn>
> 
> --- linux3-12/kernel/kmod.c	2013-11-14 09:06:58.991781656 +0000
> +++ linux3-12/kernel/kmod.c	2013-11-14 09:08:47.511781621 +0000
> @@ -217,6 +217,7 @@ static int ____call_usermodehelper(void
>  	 * Avoid propagating that into the userspace child.
>  	 */
>  	set_user_nice(current, 0);
> +	current->flags &= ~PF_NO_SETAFFINITY;

I'm a bit confused.  kernel_thread() doesn't use workqueue or
kthread_bind(), so the thread shouldn't have PF_NO_SETAFFINITY set.
Have you actually observed this happening?

Thanks.

-- 
tejun
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