linux-kernel - Re: [PATCH 1/6] cgroup: initialize cgrp->dentry before css

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Message-ID: <20130123163536.GA2373@mtj.dyndns.org>
Date:	Wed, 23 Jan 2013 08:35:36 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/6] cgroup: initialize cgrp->dentry before css_alloc()

Hello, Li.

On Wed, Jan 23, 2013 at 10:34:53AM +0800, Li Zefan wrote:
> Scheduler changes made in patch #2 are preparation for #3 and #4.
> 
> - for #3:
> 
> After ss->css_alloc(), there's a small window that tg->css.cgroup is NULL.
> With the change, tg won't be seen before ss->css_online(), so the scheduler
> won't see NULL tg->css.cgroup.
> 
> - for #4:
> 
> If tg is unregistered and removed from global list in css_free(), and if
> we kfree cgroup right after ss->css_free(), the scheduler can access
> invalid tg->css.cgroup, because tg is also protected by RCU.

Can you please incorporate the above into the patch descriptions?

Thanks!

-- 
tejun
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