Re: [PATCH v5] cgroup: Add new capability to allow a process to migrate other tasks between cgroups

From: Tejun Heo <tj@kernel.org>
To: John Stultz <john.stultz@linaro.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Li Zefan <lizefan@huawei.com>, Jonathan Corbet <corbet@lwn.net>,
	"open list:CONTROL GROUP (CGROUP)" <cgroups@vger.kernel.org>,
	Android Kernel Team <kernel-team@android.com>,
	Rom Lemarchand <romlem@android.com>,
	Colin Cross <ccross@android.com>,
	Dmitry Shmidt <dimitrysh@google.com>,
	Todd Kjos <tkjos@google.com>,
	Christian Poetzsch <christian.potzsch@imgtec.com>,
	Amit Pundir <amit.pundir@linaro.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH v5] cgroup: Add new capability to allow a process to migrate other tasks between cgroups
Date: Tue, 13 Dec 2016 13:40:57 -0500	[thread overview]
Message-ID: <20161213184057.GA17672@htj.duckdns.org> (raw)
In-Reply-To: <CALAqxLVz4WH5T7mjD1U5XG1pWQCJqsO2LWYcpJ+xDPjRb9QMig@mail.gmail.com>

Hello,

On Tue, Dec 13, 2016 at 08:08:16AM -0800, John Stultz wrote:
> On Tue, Dec 13, 2016 at 1:47 AM, Michael Kerrisk (man-pages)
> <mtk.manpages@gmail.com> wrote:
> > On 13 December 2016 at 02:39, John Stultz <john.stultz@linaro.org> wrote:
> > So, back to the discussion of silos. I understand the argument for
> > wanting a new silo. But, in that case can we at least try not to make
> > it a single-use silo?
> >
> > How about CAP_CGROUP_CONTROL or some such, with the idea that this
> > might be a capability that allows the holder to step outside usual
> > cgroup rules? At the moment, that capability would allow only one such
> > step, but maybe there would be others in the future.
> 
> This sounds reasonable to me. Tejun/Andy: Objections?

Control group control?  The word control has a specific meaning for
cgroups and that second control doesn't make much sense to me.  Given
how this is mostly to patch up a hole in v1's delegation model and how
migration operations are different from others, I doubt that we will
end up overloading it.  Maybe just CAP_CGROUP?

Thanks.

-- 
tejun