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Date: Thu, 21 Jul 2016 11:26:48 -0400
From: Tejun Heo <tj@kernel.org>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Aleksa Sarai <asarai@suse.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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        cgroups@vger.kernel.org, Christian Brauner <cbrauner@suse.de>,
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Subject: Re: [PATCH v1 3/3] cgroup: relax common ancestor restriction for
 direct descendants
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Hello, James.

On Thu, Jul 21, 2016 at 08:16:34AM -0700, James Bottomley wrote:
> > That'd be one side.  The other side is the one moving.  Let's say the
> > system admin thing wants to move all processe from A proper to B.  It
> > would do that by draining processes from A's procs file into B's and
> > even that is multistep and can race.
> 
> So the second part is that once we allow the creation of
> subdirectories, there's no unified tasks file, so there's no way of
> draining A proper without enumerating and descending into the cgroupns
> created subtrees in A?

Not that.  If it races, it will end up moving processes which are no
longer in A proper.  Such operations or distinctions might not be
meaningful under many circumstances but it'd be a pretty big hole in
the API to create and I can't really declare these holes are gonna be
okay with confidence.

Thanks.

-- 
tejun