linux-kernel - Re: [patch] Re: autogroup: sched

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Date:	Wed, 12 Jan 2011 13:40:32 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	bharata@...ux.vnet.ibm.com
Cc:	Mike Galbraith <efault@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [patch] Re: autogroup: sched_setscheduler() fails

On Wed, Jan 12, 2011 at 11:37 AM, Bharata B Rao
<bharata@...ux.vnet.ibm.com> wrote:
>> Unless I fscked up, set_task_rq() is the group change.  As soon as the
>> task's class changes, it'll be moved to the root_task_group.
>
> Ok, this is what I understand, may be Peter Z can confirm...
>
> set_task_rq() just changes the task's cfs_rq and rt_rq as per its
> task_group(). The normal way to change a task's group is to first
> change its cgroup pointer (task->cgroups, see cgroup_attach_task())
> After this you change the runqueues by calling set_task_rq() which
> now refers to new group's runqueues.
>
> In your code, I don't see where you really change task's group. AFAICS,
> it continues to remain in the same autogroup.

IMHO, task->cgroups will not change when autogroup take effect.
IOW, autogroup will only take effect when task belongs to root_task_group.

Thanks,
Yong

>
> Regards,
> Bharata.
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