netdev - Re: [PATCH v2 2/2] cgroup: get rid of populate for memcg

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Message-ID: <4F83442C.8040006@parallels.com>
Date:	Mon, 9 Apr 2012 17:18:52 -0300
From:	Glauber Costa <glommer@...allels.com>
To:	Tejun Heo <tj@...nel.org>
CC:	<netdev@...r.kernel.org>, <cgroups@...r.kernel.org>,
	<kamezawa.hiroyu@...fujitsu.com>, Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Balbir Singh <bsingharora@...il.com>
Subject: Re: [PATCH v2 2/2] cgroup: get rid of populate for memcg

On 04/09/2012 03:13 PM, Tejun Heo wrote:
> Hello,
>
> On Mon, Apr 09, 2012 at 02:51:10PM -0300, Glauber Costa wrote:
>> On 04/09/2012 02:40 PM, Tejun Heo wrote:
>>> which BTW seems incorrect even on its
>>> own - unmounting and mounting again would probably make the same
>>> notifier registered multiple times corrupting notification chain, and
>>> ref inc on the parent.
>>
>>
>> For the maintainers: Should I fix those in a new submission, or do
>> you intend to do it yourselves?
>>
>> the refcnt dropping should probably be done in my patch, it is a new
>> leak (sorry). The hotplug notifier, as tejun pointed, was already
>> there.
>>
>> It seems simple enough to fix, so if you guys want, I can bundle it in
>> a new submission.
>
> I think it would be best to create a separate patch which is routed
> through the usual memcg path (I suppose memcg patches go through
> -mm?).
>
> Thanks.
>
Tejun,

After debugging this a bit, I found most of it not to be a problem. 
Unless I am *very* wrong (and I both read and tested stuff), mount 
operations do not recreate the root cgroup. So stuff like the hotcpu 
notifier, etc, won't be a problem.

Now, you are definitely correct in pointing out that we start leaking 
stuff now - my bad.

But I guess I can then bundle it in a new submission, after shuffling 
around stuff a bit. It is really not a bug now, so no reason to route it 
separately.
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