Re: EPICS Threading Issues

[Andrew Johnson <anj@aps.anl.gov>]

Hi Richard,

On Tuesday 21 October 2008 17:25:48 Richard Pastrick wrote:
>
> If I issue a ca_get right after I create the channels in the same thread
> that created the channels, I will receive the proper value of 2.5. I can
> also use ca_put with no problem. So if I issue a command to move to 4.2
> from my program, the motor actually will move to this new location but the
> ca_get to retrieve the RBV will return 0 for the read value.
>
> So my question boils down to this, should EPICS be able use a channel that
> was created in a different thread?

Yes, if you code it properly.  If you want to call the CA library from 
different threads but using a single context like that, you need to attach to 
the same CA context in all of them.  Have a look at 
http://www.aps.anl.gov/epics/base/R3-14/8-docs/CAref.html#Client2
for information about attaching your secondary thread to the first thread's CA 
context.  Once you do that, your code should work properly (assuming you're 
handling thread synchronization properly).

Don't be afraid to ask additional questions on this list, that's what we're 
here for.

- Andrew
-- 
Talk is cheap. Show me the code. -- Linus Torvalds