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Message-ID: <1469115276.2331.23.camel@HansenPartnership.com>
Date: Thu, 21 Jul 2016 08:34:36 -0700
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Tejun Heo <tj@...nel.org>
Cc: Aleksa Sarai <asarai@...e.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Li Zefan <lizefan@...wei.com>,
Johannes Weiner <hannes@...xchg.org>,
"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
Aditya Kali <adityakali@...gle.com>,
Chris Wilson <chris@...is-wilson.co.uk>,
linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
Christian Brauner <cbrauner@...e.de>, dev@...ncontainers.org
Subject: Re: [PATCH v1 3/3] cgroup: relax common ancestor restriction for
direct descendants
On Thu, 2016-07-21 at 11:26 -0400, Tejun Heo wrote:
> 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.
So if I as the cgroup ns owner am moving a task from A to A_subdir, the
admin scanning tasks in all of A may miss this task in motion because
all the tasks files can't be scanned atomically?
James
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