Re: Asynchronous Momentary Binary Output Bug

[winans@phebos.aps.anl.gov]

>The fix is to ha ve the callback routine (after locking) check to see
>if the record is active. If it is it just reschedules itself again. It
>does this until it finds the record not active and then sets the value
>to 0 and calls dbProcess. 

*I* would say that the /fix/ would be to treat async and sync record
processing the SAME WAY... leave the record locked and inaccessable
from start to finish.  The fix you sugest is only a patch for *this*
single problem that async processing presents.

The async device support that I have written and have seen written don't
check the record values again during an async completion phase. 
Therefore if someone sneaks a value into the record during the PACT=1
idle time... it will go unnoticed... which is exactly what is causing
the problem your problem as well.

I would prefer that the solution to the momentary binary output problem
also be applicable to the general integrity problem observed in ALL
fields of a record when it is processed asynchronously.


The ability for a put (or a get) to operate on a PACT=1 record has
been a disaster waiting to happen since day 1.  I have no design ideas
on an overall solution at this time.  Only a desire to see this
annoyance go away.

If anyone has any ideas about this, I would like to hear them.  I am
sure that everyone would go along with a grand repair to this if we
only had a _reasonable_ idea on how to do it.

--John