[zeromq-dev] 0MQ 1.0.1 Python Global Interpreter Lock patch?

[Martin Sustrik]

Hi Aamir,

> I am trying to use the 0MQ 1.0.1 Python API to send / recv 0MQ
> messages in one Python thread while driving a GUI in another Python
> thread. However, whenever I use the blocking send / recv 0MQ calls,
> the whole Python process freezes and waits for network I/O (so the GUI
> becomes non-responsive, etc). It seems that pyzmq.cpp
> (http://github.com/sustrik/zeromq1/blob/master/libpyzmq/pyzmq.cpp) is
> not thread friendly. I was able to get around the problem by modifying
> the pyZMQ_receive and pyZMQ_send functions .... specifically, line 176
> in pyzmq.cpp reads:
> 
> sent = self->api_thread->send (exchange, message, block);
> 
> I replaced this with:
> 
> Py_BEGIN_ALLOW_THREADS
> sent = self->api_thread->send (exchange, message, block);
> Py_END_ALLOW_THREADS
> 
> Similarly, I changed line 192 to:
> 
> int queue;
> Py_BEGIN_ALLOW_THREADS
> queue = self->api_thread->receive (&message, block);
> Py_END_ALLOW_THREADS
> 
> 
> In summary, I just simply the 0MQ C++ blocking calls with the Python
> macros Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS, which are
> described in http://docs.python.org/c-api/init.html ... These macros
> release and reacquire the CPython Global Interpreter Lock.
> 
> 
> Is this a bug in the 0MQ 1.0.01 library that should be patched? Or is
> my patch somehow incorrect?

We knew about the problem but we haven't found a suitable solution yet. 
Your fix looks like it should solve the problem. Would you be OK with 
submitting it under MIT license?

Martin