Experimental Physics and
Industrial Control System

Mark Rivers <[email protected]> · Thu, 29 Aug 2013 13:16:57 +0000

When you created your asynPortDriver did you set the ASYN_CAN_BLOCK flag?  If so, your driver will run in its own thread that asynManager created for you.  That means the loop for record 1 is running in thread.  But record 2 also needs to run in that thread, and so it must wait until record 1 is done.  All records using that asyn port driver run in that thread.

If you don't set ASYN_CAN_BLOCK the problem will be much worse.  The loop will run in the thread that executes the channel access request.  This means the not only records for that port driver, but all records in the IOC can be hung up, since the channel access thread is blocked.

I wonder why you are trying to do this delay in the driver?  I think it would be better to do it in the database.  You can use the "seq" record to introduce a delay.  You do a caput to the seq record, and after a delay it writes to your record 1.

Mark

________________________________
From: [email protected] [[email protected]] on behalf of Vikram Bhagat [[email protected]]
Sent: Thursday, August 29, 2013 7:54 AM
To: Michael Davidsaver
Cc: [email protected]
Subject: Re: epicsThread

Hi,
   Still i don't understand how i can implement this concept in my application.   As i am using Asyn Driver, i have used 2 different reason  in asynInt32  and for 2 record.
asyn reason (1) delay    -> i put one loop which  read system time and compare with there time specified by value field of the PV by ->    caput  <PV name>   <value time>        if the system time is greater than <value time>   loop break and record processing complete with return value asynSuccess.

asyn reason (2)  currenttime   -> read current time of the system   -> it is simple scanning  record with SCAN field of 1 second.

If in project i define only one PV with any one case of above, it works fine....
But if i use 2 PV and using both function same time, when i put delay value with $ caput <PV name> <value time>   and monitor second  PV on other terminal with camonitor    <PV name (PV reading current valu)>   the second PV read out hanged till completion of first PV complete it's delay time.

Means reason (1) delay is keep execution in loop and prevent execution of other PVs   record processing.

So i think i have to run loop in separate thread and kill that thread after completion of delay time and return asynSuccess.    I am using asynDriver and it is necessory to return with asynSuccess.
Or is there any other way to do this?

from https://pubweb.bnl.gov/~mdavidsaver/epics-doc/epics-devsup.html#_asynchronous_example  example i am not able to get how to do multi threading.

With regards
Vikram

________________________________
From: Michael Davidsaver <[email protected]>
To: Vikram Bhagat <[email protected]>
Cc: "[email protected]" <[email protected]>
Sent: Monday, August 26, 2013 4:22 PM
Subject: Re: epicsThread

One mechanism for accomplishing what you ask is a delayed callback based on a timer.  When coupled with asynchronous records (what the asyn module is based on) this gives a way to have long delays in record processing without locking everything up.

For an example see

https://pubweb.bnl.gov/~mdavidsaver/epics-doc/epics-devsup.html#_asynchronous_example

Michael

On 08/26/2013 04:18 AM, Vikram Bhagat wrote:
Dear all,
      I want to know how to create and handle EPICS thread at run time.
In my application, i am using serial communication.   I am reading/writing data from serial port.
I am using Asyn driver.

In my application i have added one more functionality (asyn reason) to wait for user-define  time and then complete record processing.
In this function caput <PV name> with time in seconds will wait for that much seconds (I put one loop to read system time and check that user-defined time has been reached or not) and then "return asynSuccess".

This is working fine but problem now is->  the system is not processing any other record/PV  till the delay time will complete.  Means if i user requested delay time for 5 minutes--> the system will not process other reading or writing PV till 5 minutes complete.

How i can handle this situation? while system is waiting for time delay other record needs to be processed and have to give values or write to the output.

I think i have to create epicsThread for this delay. so it will run in separate thread and other functions can work independently. But in my case after completion of my delay i have to delete Thread ... How i can delete that Thread and make sure that my asyn driver will return asynSuccess for that delay function?

Thanks & regards
Vikram

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System