linux-kernel - Re: 3.10.16 cgroup

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Date:	Wed, 20 Nov 2013 16:47:37 -0600
From:	Shawn Bohrer <shawn.bohrer@...il.com>
To:	Li Zefan <lizefan@...wei.com>
Cc:	Hugh Dickins <hughd@...gle.com>, Tejun Heo <tj@...nel.org>,
	Michal Hocko <mhocko@...e.cz>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
	Markus Blank-Burian <burian@...nster.de>
Subject: Re: 3.10.16 cgroup_mutex deadlock

On Tue, Nov 19, 2013 at 10:55:18AM +0800, Li Zefan wrote:
> > Thanks Tejun and Hugh.  Sorry for my late entry in getting around to
> > testing this fix. On the surface it sounds correct however I'd like to
> > test this on top of 3.10.* since that is what we'll likely be running.
> > I've tried to apply Hugh's patch above on top of 3.10.19 but it
> > appears there are a number of conflicts.  Looking over the changes and
> > my understanding of the problem I believe on 3.10 only the
> > cgroup_free_fn needs to be run in a separate workqueue.  Below is the
> > patch I've applied on top of 3.10.19, which I'm about to start
> > testing.  If it looks like I botched the backport in any way please
> > let me know so I can test a propper fix on top of 3.10.19.
> > 
> 
> You didn't move css free_work to the dedicate wq as Tejun's patch does.
> css free_work won't acquire cgroup_mutex, but when destroying a lot of
> cgroups, we can have a lot of css free_work in the workqueue, so I'd
> suggest you also use cgroup_destroy_wq for it.

Well, I didn't move the css free_work, but I did test the patch I
posted on top of 3.10.19 and I am unable to reproduce the lockup so it
appears my patch was sufficient for 3.10.*.  Hopefully we can get this
fix applied and backported into stable.

Thanks,
Shawn
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