[systemd-devel] udevadm settle hangs due to veths in seperate network namespaces

Daniel P. Berrange berrange at redhat.com
Fri Jul 12 07:49:42 PDT 2013

On Fri, Jul 12, 2013 at 04:42:34PM +0200, Kay Sievers wrote:
> On Fri, Jul 12, 2013 at 4:21 PM, Kay Sievers <kay at vrfy.org> wrote:
> > On Fri, Jul 12, 2013 at 4:14 PM, Daniel P. Berrange <berrange at redhat.com> wrote:
> >> On Fri, Jul 12, 2013 at 04:10:35PM +0200, Kay Sievers wrote:
> >
> >>> Hmm, we just don't really support running udev inside of containers.
> >>> Hotplug and full OS containers have did never get any real attention
> >>> from udev running inside container setups.
> >>
> >> This example is *not* running udev in the container. The 'udevadm settle'
> >> command above is being run in the primary OS. IOW, the fact that the
> >> container has a network namespace with a veth, is breaking udevadm in
> >> the host.
> >
> > Oh, interesting. I thought you meant running 'settle' inside the container.
> >
> > That, then sounds like something we should be able cope with. I'll
> > have a look now ...
> The kernel uevents generated inside the network namespace use the same
> single global sequence number as the host, but the  events for the
> in-namespace devices are simply filtered out not to show up in the
> host.
> Settle expects to see *all* sequence numbers to wait for, and does not
> accept holes in the sequence.
> Hmm, at this moment, I have no idea how that should work, we cannot
> easily find out that these events will never show up in the host and
> we should not wait for them.
> The uevent filter hack in the kernel maybe should just be changed to
> not allocate sequence numbers of the *host* inside the namespace, and
> always compose the events inside the namespace with SEQNUM=0.

Ewww, yes, that's pretty nasty kernel behaviour/change there :-(

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