Re: Does EPICS Base support multi-thread on vxWorks 6.3?

[lorna.zhang@ni.com]

I'm not sharing a single CA client context
between threads, I did make a call to ca_context_create() with ca_disable_preemptive_callback
when a new thread is initiated.

Is there any other reason that could
cause similar issues?

Andrew, thanks for your recommendation
of using ca_enable_preemptive_callback, but that might not be my first
choice.

Lorna

From:	Andrew Johnson <anj@aps.anl.gov>
To:	tech-talk@aps.anl.gov
Cc:	lorna.zhang@ni.com
Date:	04/15/2011 11:07 PM
Subject:	Re: Does EPICS Base support multi-thread on vxWorks 6.3?

---

Hi Lorna,

On Friday 15 April 2011 02:34:53 lorna.zhang@ni.com wrote:
> 
> We developed a client based on libca (EPICS Base 3.14.9), which will
> create it's own worker thread on construction. But we found it working
> strangely on vxWorks (ppc-603). Whenever a second EPICS client is
created
> (meaning there are now 2 EPICS worker threads on vxWorks), the CPU
usage
> became 100%.
> 
> From the profile, we found the ca_pend_event is consuming lots of
the CPU.
> 
> Meanwhile, it seems epicsMutex is failing to do the lock for the second
> EPICS client??

EPICS should work fine on your hardware and OS combination, this is probably
an application programming issue.

Are these two threads sharing a single CA client context?  Hopefully
Jeff Hill 
will respond here too, but you might want to read this and the following
sections of the CA Reference Manual for some ideas:
  http://www.aps.anl.gov/epics/base/R3-14/12-docs/CAref.html#Thread
In particular if you're experienced in writing multi-threaded code you
might 
want to use ca_enable_preemptive_callback mode and completely avoid having
to 
call ca_pend_event() in your code.

- Andrew
-- 
An error is only a mistake if you don't learn from it.
When you learn something from it, it becomes a lesson.