[zeromq-dev] Deadlock with ctx_term

[Michel Pelletier]

On Fri, Nov 6, 2015 at 3:12 AM, Alexander Kampmann <
s9alkamp at stud.uni-saarland.de> wrote:

> hey,
>
I am using ZeroMQ in Java with PUSH and PULL sockets.
>
> Basically everything is working as excepted, however, sometimes the call
> to close() on the context deadlocks (jzmq makes that a term() call on
> the context). The deadlock occurs with jzmq and jeromq, and it would be
> rather strange if two implementations have the same bug, so I suspect
> that this might be an error on my part.
>

By deadlock, do you mean hang?  Deadlock is usually specifically used to
indicate two threads waiting for each other to release the same resource.

If it's hanging, have you investigated the ZMQ_LINGER option?  A true
deadlock would likely be a more serious bug.  Can you share your test case?

-Michel


>
> Do you have any advice on how to debug this? Or maybe some
> frequently-made-error which can cause this?
>
> The deadlock does not happen always, but too often (= I have a test case
> which deadlocks approximately every fifth execution). As I said, the
> deadlock happens for both, jzmq and jeromq. When I attach my debugger to
> jeromq, I can see that the reaper-thread terminated, but the sockets
> list in the context still contains a PUSH socket. destroy() has not been
> called on the socket.
>
> I think that close() is called, because I am using a try-with-resource
> when I create the socket. If it indeed has not been called, this is a
> bug in the java-8-compiler. I tried to confirm that close has been
> called, but if I set a breakpoint or add a printout in the close()
> method, the deadlock would not occur. It did reappear after I removed
> the breakpoint/printout.
>
> Best regards,
> Alex
>
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