Re: [Qemu-devel] [RFC PATCH V2 2/5] qapi: add event helper functions

[Eric Blake <eblake@redhat.com>]

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On 01/06/2014 03:23 PM, Luiz Capitulino wrote:
> On Fri,  3 Jan 2014 07:10:31 +0800
> Wenchao Xia <xiawenc@linux.vnet.ibm.com> wrote:
> 
>> This file hold some functions that do not need to be generated.
>>
>> Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
>> ---

>> +static void timestamp_put(QDict *qdict)
>> +{
>> +    int err;
>> +    QObject *obj;
>> +    qemu_timeval tv;
>> +
>> +    err = qemu_gettimeofday(&tv);
>> +    if (err < 0) {
>> +        return;
>> +    }
> 
> Hmm, I see this has always existed (and I guess I did it myself), but it's
> not quite right. Sending an event w/o time info wouldn't be complaint to
> the protocol spec. It's a good idea to fix this now. We have three options:
> 
>  1. abort()
> 
>  2. Skip sending the event altogether
> 
>  3. Add a bogus time value (say seconds=0 and microseconds=0)
> 
> I don't know what's best, but I guess I'd do item 3. Although I wonder
> if zero is any better then no info at all (it's certainly complaint, but
> not a valid info). Maybe skip the event then?

I have a patch pending[1] for libvirt (missed libvirt 1.2.2, but will be
in 1.2.3) that exposes raw qemu events through libvirt-qemu.so
(basically, as a debugging aid, similar to libvirt's 'virsh
qemu-monitor-command', it will add 'virsh qemu-monitor-event').  In my
implementation, I documented that seconds=-1 implies a missing timestamp
(at which point microseconds is ignored, but can be set to 0).  So I'm
in favor of option 3, but with -1 rather than 0 for seconds.

[1]https://www.redhat.com/archives/libvir-list/2014-February/msg00000.html

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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