Experimental Physics and
Industrial Control System

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.

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?

Replies:

Re: monitors received out of order Tim Mooney

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monitors received out of order Tim Mooney

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