Hi Matt,
In asynManager there are 4 queues per port. There are 3 queues for I/O requests with different priorities (asynQueuePriorityLow,asynQueuePriorityMedium,asynQueuePriorityHigh), and 1 for connection requests (asynQueuePriorityConnect). Each call to pasynManager->queueRequest specifies which priority queue to use. Standard asyn device support uses 0 (asynQueuePriorityLow) for all requests.
Mark
________________________________
From: [email protected] on behalf of Pearson, MR (Matthew)
Sent: Wed 5/20/2009 5:23 AM
To: [email protected]
Subject: Process ordering in CA and asyn
Hi,
I'm currently investigating a possible race condition in our motor
control software. In our motor controller driver we are setting a
parameter by using a BO record writing to an Asyn port.
Then we are setting a series of other parameters using the Asyn motor
device support layer (via the motor record), which is talking through
the same Asyn port as the BO record.
Then at the end we are setting again the BO record flag.
So my question is really about guaranteeing the process ordering of
these records, as well as making sure that the same ordering is
preserved in Asyn.
I know channel access has a sequence ID that the channel access server
uses to re-order CA events on the IOC, and process them in sequence
order number (is that right?).
On my client side, I do a series of ca_put()s, and call ca_pend_event()
after each one. But I understand that the CA client is not guaranteed to
service the event when calling ca_pend_event(). So is the CA sequence
number assigned to an event at the ca_put() stage, or the at the
ca_pend_event() stage?
Now on to Asyn... The device support layers for the BO and motor records
are connecting to the same Asyn port. Does the asynManager set up
different queues for each device support layer type? Or is it one queue
per port?
I am worried that if there are different queues for the motor records
and the BO record, then it is possible that the processing could be done
out of order in the scan task at this low level, even though processing
was initiated *in* order at the record level.
In the asyn documentation is does say that a thread handling a queue is
dedicated to a specific port, so I think that means that there is indeed
only one queue per port.
Cheers,
Matthew
DLS Controls
This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail.
Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd.
Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message.
Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom
- References:
- Process ordering in CA and asyn Pearson, MR (Matthew)
- Navigate by Date:
- Prev:
RE: Process ordering in CA and asyn Rees, NP (Nick)
- Next:
Re: Can the saveData config file referencence another file? Tim Mooney
- 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
- Navigate by Thread:
- Prev:
RE: Process ordering in CA and asyn Rees, NP (Nick)
- Next:
Can the saveData config file referencence another file? Mark Bennett
- 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
|