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Date: Fri, 23 Sep 2011 15:00:15 +0800
From: Li Zefan <lizf@cn.fujitsu.com>
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To: Mike Galbraith <mgalbraith@suse.de>
CC: LKML <linux-kernel@vger.kernel.org>, Paul Menage <paul@paulmenage.org>,
        David Rientjes <rientjes@google.com>
Subject: Re: [patch] cpusets: allow PF_THREAD_BOUND kworkers to escape from
 a cpuset
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cc David, who added this restriction

于 2011年09月23日 14:21, Mike Galbraith wrote:
> 
> kworkers can be born in a cpuset, leaving them adrift on an unsinkable ship.
> Allow them to be moved to the root cpuset so the cpuset can be destroyed.
> 
> Signed-off-by: Mike Galbraith <efault@gmx.de>
> 

I've noticed this long ago, so..

Acked-by: Li Zefan <lizf@cn.fujitsu.com>

> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> index 10131fd..b26f4c4 100644
> --- a/kernel/cpuset.c
> +++ b/kernel/cpuset.c
> @@ -1384,7 +1384,7 @@ static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
>  	 * set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may
>  	 * be changed.
>  	 */
> -	if (tsk->flags & PF_THREAD_BOUND)
> +	if (tsk->flags & PF_THREAD_BOUND && cont->parent)

To make the code more self-explanatory, I think this is a bit better:

	if (... && cont != cont->top_cgroup)

>  		return -EINVAL;
>  
>  	return 0;
>