Experimental Physics and
Industrial Control System

"Denison, PN \(Peter\)" <[email protected]> · Tue, 18 Sep 2007 11:20:17 +0100

> I'm trying to debug a deadlock on Linux under R3.14.8.2, on a 
> cut down IOC with only asyn, motor and autosave installed. 
> 
> What appears to be happening is that one thread is waiting on 
> an epicsEvent, whilst another thread is trying to signal that 
> event, but getting stuck on the event's internal lock. The 
> pthread man pages imply that this shouldn't happen.

There's nothing quite like asking in public to find out you've been
stupid, is there? Emerging from my brown-paper-bag, I've found the cause
of the problem. However, I think there is still room for improvement, as
the library code could have caught it, rather than deadlocking.

I was trying to signal an epicsEvent after having called
epicsEventDestroy() on it. Therefore the lock it was trying to acquire
was 0.

Is this a reason to put a cookie in the epicsEventOSD structure, to
check that it's a valid structure before using it? If the consensus is
that it's worth it, I'll get hacking.

-- 
Peter Denison, Senior Software Engineer, Diamond Light Source Ltd.
Tel: +44 1235 778511
(apologies in advance for the lines below. Some bits are a legal
requirement and I have no control over them)

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System