Re: [Qemu-devel] monitor: enable OOB by default

[Peter Xu <peterx@redhat.com>]

On Thu, Jun 28, 2018 at 09:04:19AM +0200, Markus Armbruster wrote:
> Eric Blake <eblake@redhat.com> writes:
> 
> > On 06/27/2018 07:07 AM, Peter Xu wrote:
> >
> >>>> Worse than that - broadcasting to all monitors is categorically broken.
> >>>> Different monitors make use the same "id" formatting scheme, so if you
> >>>> broadcast COMMAND_DROPPED to a different monitor you might have clashing
> >>>> "id" and thus incorrectly tell a client its command was dropped when in
> >>>> fact it was processed. You'd have to be fairly unlucky in timing, but
> >>>> it could happen.
> >>>
> >>> Right.  Must fix bug.
> >>
> >
> >>
> >> My current plan is that I can touch up scripts/qapi/events.py and
> >> related stuff to allow QMPEventFuncEmit to take a monitor parameter,
> >> then we pass in NULL when we want to send the event to all monitors.
> >>
> >> Would that work?
> >
> > Makes sense to me. Also, right now, ALL callers of qapi_event_send_*
> > pass &error_abort as their final parameter. If you're refactoring
> > everything anyways, you could get rid of that parameter on the
> > presumption that it doesn't buy us anything.
> 
> Let me try to turn presumption into fact :)
> 
> The generated qapi_event_send_FOO() can detect the following error
> conditions:
> 
> * Visitor fails.  But the QObject output visitor can't actually fail.
> 
>   Since the errp parameter is part of the abstract visitor interface, we
>   can't eliminate it.  We can pass &error_abort.
> 
> * emit() function fails.  Can't happen, either.
> 
>   Let's eliminate the unused errp parameter of QMPEventFuncEmit.

Hmm, I think I got your point.

> 
>   If we can eliminate the somewhat silly indirection through
>   qmp_event_get_func_emit(), even better.

It confused me before on why we had that after all. Let me give it a
shot.

Regards,

-- 
Peter Xu