Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Thu, 23 Jul 2009 13:54:15 +0200

Hi Michael,

There have always been issues with "I/O Intr" mode but I thought that version 2

is more stable than version 1. Unfortunately asynDriver does not natively

support unsolicited messages from a device -- at least not without blocking the

port for all other users. Thus I have to poll frequently for new messages. This

makes the code quite hard to debug. (Messages during polling would flood the

screen and change the timing behavior of the system.)

Changing SCAN from "I/O Intr" to anything else aborts the currently running

protocol. Going back to "I/O Intr" restarts the protocol. Thus I guess the

record is waiting for a reaction (data or timeout) and sees neither. The driver

_should_ restart a timer in that case and try again later. It seems this does

not happen. It may be a race condition somewhere in the code (e.g. between

timeout and incoming data). That would explain the rare occurrence.

At the moment, I do not have much time but I will have a look at the problem in

August.

Dirk

Michael Abbott wrote:

Dear Dirk,

I'm sorry this isn't a more helpful report, but I'm continuing to see

problems with stream Device version 2 (my latest test was with version

2.4, I believe) with I/O Intr records.

For a long time (a couple of years, I think) my IOCs would see crashes

when using stream Device v2 on my configuration (which I'll describe in a

moment), so I'm currently running them with stream Device v1 (ported to

3.14). There were some bug fixes in the last year which seem to have

removed the crashes (I think there was some stack overflow). I believe

you've been in communication with some of my colleagues on this.

Unfortunately, in my latest test with v2, I see the following behaviour:

records with I/O Intr processing will suddenly stop processing. This is

*very* rare, on around thirty IOCs I saw this occur twice in a fortnight.

Curiously, if the .SCAN field is changed to Passive and back to I/O Intr

then processing resumes normally!

My IOCs are configured with Hytec 8516 RS-485 cards connected to CMS ION

radiation monitors which send long packets with many fields to decode. A

packet is automatically sent every second, and one record is configured

with SCAN="I/O Intr", and processes the remaining 14 fields contained in

the record. I'm using asyn version 4-10 (and a fair number of other

components on each IOC).

It's a difficult bug to track down, as it seems almost unreproducible, but

alas it occurs often enough that I can't run v2 on my IOCs. I know that

some of my colleagues also see intermittent I/O Intr related issues, but I

don't have details.

I wish I could be more helpful!

	Michael Abbott

--
Dr. Dirk Zimoch
Paul Scherrer Institut, WBGB/006
5232 Villigen PSI, Switzerland
Phone +41 56 310 5182

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System