Re: monitors received out of order

["Ernest L. Williams Jr." <ernesto@slac.stanford.edu>]

Tim Mooney wrote:
> Dear folks,
>
> I have two records, and a separate task monitoring a field that both records
> post, all in the same IOC.  Most of the time, my task receives monitors in the
> order in which they were posted.  But sometimes, the task receives a monitor
> from record B before it receives a previously posted monitor from record A.
> (I know for sure which record is posting first, because record A posts before
> causing record B to process.  Also, I've modified the record to set its time
> stamp immediately before posting, and I get another time stamp on entry to
> the monitor routine.  The time ordering of those stamps does not agree.)
> I've seen this on solaris and Linux, but not on vxWorks.
>   
Hi Tim,

When you run an IOC on Linux the EPICS Priorities are not map properly 
unless you run the IOC as root.
All tasks are given the same OS priority.
Are you running the Linux IOC as root?




> I have code that misbehaves when this happens, so I started digging around
> and have convinced myself that I should not be relying on the time ordering of
> monitors received from different records (even when those records are running
> in the same task).  I now think I can rely on posts from a single record arriving in
> time order, but not posts from different records.  I think this because events from
> different record go into different queues, and there doesn't seem to be any code
> in the vicinity that seems worried about time ordering across event queues.
>
> Am I right about this?
>
>