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Date: Mon, 19 Mar 2012 09:15:07 -0700
From: Tejun Heo <tj@kernel.org>
To: Glauber Costa <glommer@parallels.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, lizf@cn.fujitsu.com,
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Subject: Re: [PATCH 06/10] cgroup: convert memcg controller to the new
 cftype interface
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Hey,

On Mon, Mar 19, 2012 at 02:43:14PM +0400, Glauber Costa wrote:
> I am still in the middle of the review. Is it possible to dynamically
> register entries? (right now, I mean)

Before the patchset, no.  After the patchset, yes.

> If yes - which seems to be a bit of the point of the exercise, so it
> should be totally okay from my PoV. I have that call in populate because
> which files will be created depends on which protocols you have registered.
> 
> The trick here, is that doesn't need to happen at all cgroup creations.
> But it can't happen at root's either, because this is quite fragile:
> some protocols may only be registered after root memcg is created.

Yeah, it can happen anytime but it shouldn't be called from ->create()
or other callbacks which are invoked under cgroup_mutex.  We can
provide an alternative interface or other locking trickery to avoid
this, but I don't think I'll take that path unless there are very
strong rationale.

Thanks.

-- 
tejun