Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Mon, 11 Jun 2007 15:03:08 -0500

Hi Till,
Till Straumann wrote:

In my case though, the <defunct> process' parent is still the original
cau thread, and when the parent exits so does the defunct thread.

I'm not familiar with the internals of cau. However, note that the bug I
reported bites only if

a thread with an associated exit handler that synchronizes with the
tread's termination

(the 'errlog' thread is an example for such a thread) is already running
prior to

the attempt to spawn the caRepeater.

Ok, that explains the different cleanup behavior that I saw. I agree
with your fix, which I have just committed to CVS.
Another problem though appears to be that at no point does the CA
client library actually fork off a caRepeater itself, even after this
message appears:
  CA client library is unable to contact CA repeater after 50 tries.
  Silence this message by starting a CA repeater daemon
  or by calling ca_pend_event() and or ca_poll() more often.

I'm afraid I don't understand. With caRepeater on the PATH everything works

as expected for me (3.14.9). E.g., the test program I submitted with my

last post succeeds in spawning a repeater and I see it running and
listening

on port 5056.

Right, if a caRepeater program is found then everything works fine; I
was still testing the case where caRepeater is not in the path, and was
expecting the CA client library to fork itself again and run the CA
repeater code in the child fork in that case. The CA library used to do
that to ensure that there would always be a repeater running when it
needed one, but I think people got confused because if they didn't run
caRepeater from their machine's startup the forked first client that
they started would become the repeater for the machine, and they'd
wonder why their MEDM or ALH or whatever program it actually was
continued to run after they'd shut it down. I now vaguely remember Jeff
discussing the idea of taking that behavior out, and it looks like he
did, so maybe it isn't a bug after all.
Thanks,
- Andrew
--
The right to be heard does not automatically include
the right to be taken seriously. -- Hubert H. Humphrey

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System