[Libvir] Remote & the problem with qemu deadlock
Richard W.M. Jones
rjones at redhat.com
Thu Apr 19 10:49:23 UTC 2007
Daniel Veillard wrote:
> On Wed, Apr 18, 2007 at 04:33:58PM +0100, Richard W.M. Jones wrote:
>> Daniel Veillard wrote:
>>> Can we recognize that the connection is on localhost and just serve
>>> the request directly and synchronously instead ?
>> Yes you can. In real terms what this would mean is that all the
>> functions in qemu_internal.c are changed so that they become:
>>
>> static int qemuDestroyDomain(virDomainPtr domain) {
>> qemud_packet_client req;
>> qemud_packet_server reply;
>> qemuPrivatePtr priv = (qemuPrivatePtr) domain->conn->privateData;
>>
>> req.data.type = QEMUD_CLIENT_PKT_DOMAIN_DESTROY;
>> req.data.qemud_packet_client_data_u.domainDestroyRequest.id =
>> domain->id;
>>
>> #if QEMU_INTERNAL_IS_REALLY_LINKED_TO_THE_SERVER
>> /* some code to get the fake server & client, and then: */
>> qemudDispatchDomainDestroy (server, client, req, rep);
>> /* followed by some code to decode the fake "reply packet" */
>> #else /* existing code: */
>> if (qemuProcessRequest(domain->conn, priv->qemud_fd, NULL, &req,
>> &reply) < 0) {
>> return -1;
>> }
>>
>> return 0;
>> #endif
>> }
>>
>> So it can be done but qemu_internal is sure going to look ugly afterwards.
>
> Maybe you can centralize the dispatcher one level up and keep it like
> a driver, this could avoid the issue, no ?
The individual driver calls (qemuDestroyDomain, etc.) are called from
the driver table, and since the qemud calls aren't compatible I can't
see how to do it except to special-case every call.
The real issue though is summarised in the attached diagram. I'm
proposing that we don't hack qemu_internal in the above way (top
diagram, dot-dash line) when in the long term that should all be going
away (bottom diagram). Note that this hack only affects
qemu-over-remote. Current usage of qemu continues same as before.
Rich.
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