Re: [libvirt] [RFC PATCH] lxc: don't return error on GetInfo when cgroups not yet set up

["Serge E. Hallyn" <serge hallyn canonical com>]

Quoting Daniel P. Berrange (berrange redhat com):
> On Wed, Sep 28, 2011 at 02:14:52PM -0500, Serge E. Hallyn wrote:
> > Nova (openstack) calls libvirt to create a container, then
> > periodically checks using GetInfo to see whether the container
> > is up.  If it does this too quickly, then libvirt returns an
> > error, which in libvirt.py causes an exception to be raised,
> > the same type as if the container was bad.
> lxcDomainGetInfo(), holds a mutex on 'dom' for the duration of
> its execution. It checks for virDomainObjIsActive() before
> trying to use the cgroups.

Yes, it does, but

> lxcDomainStart(), holds the mutex on 'dom' for the duration of
> its execution, and does not return until the container is running
> and cgroups are present.

No.  It calls the lxc_controller with --background.  The controller
main task in turn exits before the cgroups have been set up.  There
is the race.

-serge