On 05/14/2012 11:06 AM, Michal Privoznik 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.
I think the point was that you would block endlessly waiting for the
{'return':{}} anyways, even with the old implementation, because there
was no guarantee that the guest agent could issue the reply in a timely
manner. Therefore, the only sane implementation in libvirt is to assume
that success will not be reported via the guest agent, and that libvirt
must _always_ probe for the listed side effects (a change in guest
status, qemu exiting, an event, or so forth), and optionally have a
timeout if the associated timeout does not occur in a reasonable time.
--
Eric Blake ebl...@redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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