Re: [Qemu-devel] Dropping the MONITOR_CMD_ASYNC

[Anthony Liguori <anthony@codemonkey.ws>]

On 12/11/2011 04:29 AM, Alon Levy wrote:
> On Thu, Dec 08, 2011 at 05:45:44PM -0200, Luiz Capitulino wrote:
>> Hi there,
>>
>> I'm about to completely drop the MONITOR_CMD_ASYNC API, but it turns out that
>> the command client_migrate_info uses it. That's a legacy interface and has to
>> be dropped, no command should be using it...
>>
>> Something tells me that if I just drop it (and change the command to use the
>> regular interface), bad things will happen. Am I right? :)
>>
>
> The monitor command client_migrate_info needs to complete after getting

Then it's completely broken.  CMD_ASYNC is broken and should have been removed a 
long time ago.

Unfortunately, we're going to have to remove this command until we can move to 
full QAPI.  I see this went in through Gerd's tree:

commit edc5cb1a52b2847201acf78b0fba67ab3c2464d5
Author: Yonit Halperin <yhalperi@redhat.com>
Date:   Mon Oct 17 10:03:18 2011 +0200

     spice: turn client_migrate_info to async

Changes to monitor commands really should at least carry an Acked-by from the 
QMP maintainer (Luiz).  That would have prevented this from happening.

I'll try to be more diligent about enforcing this in the future.

Regards,

Anthony Liguori

> an ACK message from the currently connected spice client (this is the
> only case where this is required - if there is no client then the
> MONITOR_CMD_ASYNC API won't be used). This in turn requires the main
> thread to perform select and call the callback that will process this
> ACK. That's why the MONITOR_CMD_ASYNC API was used.
>
> I'm not aware of any other way to do this, I'll be glad for any help
> here. Also, I understand this is not what is not true async, since one
> would expect a true async interface to support multiple in flight
> monitor commands. If there is any ETA or existing way to do this we
> could change the implementation of client_migrate_info.
>
> Alon
>
>