Hi Dirk,
On 2012-07-05 Dirk Zimoch wrote:
>
> Consider a client that subscribes for two PVs (here in particular two
> fields of the same record). Now the IOC (the record support) posts
> events on both fields. Is the time order of these two events preserved?
>
> In other words, are the monitor callbacks of the client called in the
> same order as the IOC calls db_post_events()?
>
> In my particular case, I have a client (with unknown source code) that
> sometimes sees value changes on two fields of the motor record, DMOV and
> RRBV, in the wrong order. Thus in the DMOV callback, RRBV still has the
> old value. I checked in the motor record that DMOV is always posted
> after RRBV.
>
> Is there any mechanism in EPICS that could swap the execution order or
> should the problem be searched in the client?
Yes, the IOC server's event queue is not strictly ordered before R3.15. This
issue is described in the tech-talk email thread pointed to by the "full
specification" link on this page:
https://blueprints.launchpad.net/epics-base/+spec/strict-ordered-event-queue
- Andrew
--
Never interrupt your enemy when he is making a mistake.
-- Napoleon Bonaparte
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