Re: [Qemu-devel] [PATCH 0/2]: qemu-ga: make shutdown & suspend synchronous

[Luiz Capitulino <lcapitulino@redhat.com>]

On Mon, 14 May 2012 19:06:28 +0200
Michal Privoznik <mprivozn@redhat.com> wrote:

> On 11.05.2012 21:19, Luiz Capitulino wrote:
> > The main motivation for this series is fixing two possible race conditions
> > in the guest-suspend-* API due to the complexity that arose from the way
> > we handle terminated children processes today. Full details in the first
> > patch.
> > 
> > This series applies on top of my two other qemu-ga series submitted
> > previously:
> > 
> >  http://lists.gnu.org/archive/html/qemu-devel/2012-05/msg00999.html
> > 
> >  http://lists.gnu.org/archive/html/qemu-devel/2012-05/msg01507.html
> > 
> >  qapi-schema-guest.json   |   56 ++++++++++------
> >  qapi/qmp-core.h          |   10 ++-
> >  qapi/qmp-dispatch.c      |    8 ++-
> >  qapi/qmp-registry.c      |    4 +-
> >  qemu-ga.c                |   40 ++++++------
> >  qga/commands-posix.c     |  162 ++++++++++++++++++----------------------------
> >  qga/guest-agent-core.h   |    4 ++
> >  scripts/qapi-commands.py |   14 +++-
> >  8 files changed, 154 insertions(+), 144 deletions(-)
> > 
> 
> Okay, this is definitely an enhancement and fix of bogus implementation.
> One thing that I'd like to ask is - how can user distinguish between
> these implementations. I am asking basically from libvirt POV.
> Because if I assume I am dealing with the previous implementation and
> thus waiting for the {'return':{}} before I can return form an API, but
> the GA actually uses the new implementation I will block endlessly.

There's no way to distinguish. It's a bug to wait for an OK response for
the guest-shutdown and guest-suspend-*, because a response may not been
sent even before this series (and this is correctly documented).