linux-kernel - Re: [PATCH?] race between cgroup_subsys->fork() and cgroup

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Message-ID: <20151125204057.GF14240@htj.duckdns.org>
Date:	Wed, 25 Nov 2015 15:40:57 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Aleksa Sarai <cyphar@...har.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Li Zefan <lizefan@...wei.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH?] race between cgroup_subsys->fork() and cgroup_migrate()

On Wed, Nov 25, 2015 at 02:54:10PM -0500, Tejun Heo wrote:
> On Wed, Nov 25, 2015 at 02:51:38PM -0500, Tejun Heo wrote:
> > Sounds perfect.  As this needs to go through -stable, can you please
> > resend the patch with proper description and SOB?  Please also update
> > the now incorrect comment in can_attach.
> 
> Ooh, the patch triggers RCU warning from task_css().  It's spurious
> and I think the right thing to do at least for now is using
> task_css_check() and explain what's going on.

And I spotted a bug in cgroup core in controller enable path.  While
the race between fork and attach exists and needs to be fixed, I think
the cgroup core bug is the main source of discrepancy.  Will update
once I learn more.

Thanks.

-- 
tejun
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