Re: [Qemu-devel] [Qemu-stable] qmp commands get rejected

[mdroth]

On Sun, May 26, 2013 at 05:13:36PM +0200, Stefan Priebe wrote:
> Am 26.05.2013 03:23, schrieb mdroth:
> >On Sat, May 25, 2013 at 01:09:50PM +0200, Stefan Priebe wrote:
> >>Am 25.05.2013 00:32, schrieb mdroth:
> >>>On Sat, May 25, 2013 at 12:12:22AM +0200, Stefan Priebe wrote:
> >>>>Am 25.05.2013 00:09, schrieb mdroth:
> >>>>>>>>>I would try to create a small example script.
> >>>>>>>>
> >>>>>>>>I use qmp-shell and other little scripts very often.
> >>>>>>>>
> >>>>>>>>>Am this be due to the fact that I don't wait for the welcome banner
> >>>>>>>>>right now?
> >>>>>>>>
> >>>>>>>>If you're not reading from the socket, then you'll get the banner back
> >>>>>>>>when
> >>>>>>>>you read your first response. But qom-set shouldn't fail because of 
> >>>>>>>>that.
> >>>>>>
> >>>>>>I can workaround it by adding this patch:
> >>>>>>diff --git a/monitor.c b/monitor.c
> >>>>>>index 62aaebe..9997520 100644
> >>>>>>--- a/monitor.c
> >>>>>>+++ b/monitor.c
> >>>>>>@@ -4239,7 +4239,8 @@ static int monitor_can_read(void *opaque)
> >>>>>>  static int invalid_qmp_mode(const Monitor *mon, const char *cmd_name)
> >>>>>>  {
> >>>>>>      int is_cap = compare_cmd(cmd_name, "qmp_capabilities");
> >>>>>>-    return (qmp_cmd_mode(mon) ? is_cap : !is_cap);
> >>>>>>+//    return (qmp_cmd_mode(mon) ? is_cap : !is_cap);
> >>>>>>+    return ((is_cap > 0) ? 0 : (qmp_cmd_mode(mon) ? is_cap : !is_cap));
> >>>>>>  }
> >>>>>
> >>>>>I think this is unrelated to your original issue. If you issue
> >>>>>'qmp_capabilities' command more than once you will get CommandNotFound,
> >>>>>and that behavior seems to be present even with v1.3.0. This patch seems
> >>>>>to be masking the problem you're having (which seems to be state from
> >>>>>previous monitor sessions/connections leaking into subsequent ones).
> >>>>
> >>>>That sounds reasonable. I'm using proxmox / PVE which does a lot of
> >>>>qmp queries in the background. So i might see situations where X
> >>>>connections in parallel do qmp queries.
> >>>>
> >>>>>It's possible the GSource-based mechanism for handling I/O for chardev
> >>>>>backends is causing a difference in behavior. Still not sure exactly
> >>>>>what's going on though.
> >>>>Can i revert some patches to test?
> >>>
> >>>I think somewhere prior to this one should be enough to test:
> >>>
> >>>2ea5a7af7bfa576a5936400ccca4144caca9640b
> >>
> >>YES! I used 2ea5a7af7bfa576a5936400ccca4144caca9640b~1 for my tests
> >>and this works absoluty fine.
> >
> >Turns out the real culprit was a few commits later:
> >
> >9f939df955a4152aad69a19a77e0898631bb2c18
> >
> >I've sent a workaround this fixes things for QMP, but we may need a more
> >general fix. Please give it a shot and see if it fixes your issues:
> >
> >http://article.gmane.org/gmane.comp.emulators.qemu/213106
> 
> no i got again:
> The command qom-set has not been found  JSON Reply: {"id":
> "21677:2", "error": {"class": "CommandNotFound", "desc": "The
> command qom-set has not been found"}} JSON Query: 
> {"execute":"qom-set","id":"21677:2","arguments":{"value":2,"path":"machine/peripheral/balloon0","property":"guest-stats-polling-interval"}}
> at /usr/share/perl5/PVE/QMPClient.pm line 101.

Darn, I noticed another potential race after I sent the patch. Hadn't
been able to trigger it on my end, but it might be what you're hitting.

Just sent a v2, can you give that a shot?

http://article.gmane.org/gmane.comp.emulators.qemu/213147

> 
> Stefan
>