[CRIU] [PATCH 1/2] finalize cgroups correctly

[Tycho Andersen]

On Thu, Mar 19, 2015 at 09:55:23PM +0300, Pavel Emelyanov wrote:
> On 03/19/2015 09:46 PM, Tycho Andersen wrote:
> > On Thu, Mar 19, 2015 at 10:41:58AM -0700, Saied Kazemi wrote:
> >> Hi Tycho,
> >>
> >> I tried the patch but it didn't work for me as cgyard is visible after
> >> restore (please see below).  Here are criu dump and restore commands.  I've
> >> also attached the log files.
> >>
> >> criu dump -v4 -D /home/saied/work/nsinit/busybox/nsinit/checkpoint -o
> >> dump.log --root /home/saied/work/nsinit/busybox --manage-cgroups
> >> --evasive-devices -t 31361
> >>
> >> criu restore -v4 -D /home/saied/work/nsinit/busybox/nsinit/checkpoint -o
> >> restore.log --root /home/saied/work/nsinit/busybox --pidfile
> >> /home/saied/work/nsinit/busybox/nsinit/restoredpid --manage-cgroups
> >> --evasive-devices --inherit-fd fd[0]:pipe:[69253] --inherit-fd
> >> fd[1]:pipe:[69254] --inherit-fd fd[2]:pipe:[69255]
> >>
> >> Any ideas why?!
> > 
> > I think it's because fini_cgroup is broken. It doesn't unmount the
> > individual controllers before trying to unmount the cg yard.
> 
> That was done deliberately :) It does MNT_DETACH umount. Which, in
> turn, detaches all the sub-mounts of the detached mount immediately :)

Oh, right, I somehow missed the MNT_DETACH flag. I'm not sure what the
deal is then, I'll take a look.

> > Another problem I realized is that the properties restore code doesn't
> > seem to respect the manage_cgroups flag (although I can't tell why it
> > doesn't cause problems for more people, since it seems like it should
> > blow up without that flag right now).
> 
> I guess it's because the list of controllers being empty without the
> --manage-cgroups flag, is it?

Yeah, that's probably true. Then it would only break if someone
supplied --manage-cgroups on dump but not restore. Is this something
we care about? I can fix it too with this series if so.

Tycho

> > So, I think we need this patch but it isn't sufficient. We can drop
> > the series for now and I'll try and come up with a patch to unmount
> > things in the right order too.
> > 
> > Tycho
> 
> Thanks,
> Pavel
>