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<== Date ==> <== Thread ==>

Subject: Another strange CA observation
From: Benjamin Franksen <benjamin.franksen@helmholtz-berlin.de>
To: <tech-talk@aps.anl.gov>
Date: Wed, 10 Jul 2013 13:22:25 +0200
Hello

in order to write a regression test for my latest sequencer bugfix, I need to
persuade CA to respond to a ca_get_callback request with a certain delay, so
that I get a timeout and we can see if the variable recovers as it should.

I know how to do it for ca_put_callback, that's easy. But no matter what I
try, I have not been able to do it for ca_get_callback, i.e. I always get the
callback immediately.

I even went so far as to use a subroutine record with an epicsThreadSleep in
the subroutine (disclaimer: don't try that at home or in a production
system!). Then I caput to the PROC field to let the record process and
immediately after that do the ca_get_callback. I expected the callback to
arrive only after the record no longer holds the scan lock i.e. after the
epicsThreadSleep expires, but this is not the case: I do get the callback
immediately, and not even with an error status.

I am a bit perplexed by this: how can CA get the VAL from the record if
processing is holding the scan lock?

Is there any other way to delay the response to a get request?

Cheers
Ben
--
"Make it so they have to reboot after every typo." ― Scott Adams


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Replies:
Re: Another strange CA observation Benjamin Franksen

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