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Re: [Libvir] Remote & the problem with qemu deadlock



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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