[CRIU] [PATCH] zdtm: add a small program to create a zdtm container

[Andrew Vagin]

On Tue, Aug 12, 2014 at 03:46:27PM -0400, Christopher Covington wrote:
> On 08/12/2014 03:17 PM, Andrew Vagin wrote:
> > On Tue, Aug 12, 2014 at 02:34:20PM -0400, Christopher Covington wrote:
> >> Hi Andrey
> >>
> >> On 08/12/2014 12:13 PM, Andrey Vagin wrote:
> >>> I didn't find a way how to do that with help "unshare".
> >>> It's simpler to write this program. It looks better than tricks in
> >>> zdtm.sh.
> >>
> >> How different is this from `criu restore -n mnt,pid,net,ipc`?
> > 
> > I don't understand the question. This program is used to execute zdtm.sh
> > in a container to avoid races between tests.
> > The most popular race condition is when one test takes PID of another
> > test, and the second test can't be restored.
> 
> I guess I don't understand the -n, --namespace option to CRIU since I never
> seemed to be able to get it to work. My intuition would be that it is supposed
> to do the "interesting task" you describe below. Digging in to the matter, I
> think I see why I've never gotten it to work:
> 
> commit ac845bd1d8f7298e97b779f587a1fb46dd5737a7
> Author: Pavel Emelyanov <xemul at parallels.com>
> Date:   Thu Jan 17 18:14:55 2013 +0400
> 
>     cr: Obsolete the --namespaces option
> 
>     It's no longer required to use this option -- two currently
>     supported cases (tasks on host and tasks in containers) can
>     be detected automatically. Keep this option for future.
> 
> > Maybe you mean that a test can be restored in a new pid namespace.
> > Currently criu can't do that. Here is a few questions. Who will be
> > the init process? The root task probably doesn't ready to be a sub-reaper.
> > Do we need to remount /proc? If the answer is yes, we need to create
> > a new mount namespace together with pidns.
> > I think this is interesting task, which will be one day implemented.
> 
> Why not simply move the contents of test/zdtm_ct.c into crtools.c, executed
> conditionally based on -n, --namespace, and call it initially implemented?

Personally I'm not sure that we need this. Each one can execute "unshare"
and setup a container how he wants. Then he/she executes "criu restore"
and has the expected result.

If you look at zdtm_ct, you can find that it mounts /dev/pts. I'm not
sure, that each one will want to do that. I'm afraid if we will apply
needs of all users, in a one moment we will have another lxc in the
CRIU source.

> 
> Christopher
> 
> -- 
> Employee of Qualcomm Innovation Center, Inc.
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