1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 <2010> 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 | Index | 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 <2010> 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
<== Date ==> | <== Thread ==> |
---|
Subject: | Re: monitors received out of order |
From: | "Ernest L. Williams Jr." <[email protected]> |
To: | Tim Mooney <[email protected]> |
Cc: | EPICS tech-talk <[email protected]> |
Date: | Tue, 02 Nov 2010 08:17:00 -0700 |
Dear folks,Hi Tim,
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?