Re-Occurrence of bug #199 in code based on gr_bin_statistics_f

Hello all,

It looks as though I have uncovered GNU Radio bug #199 in one of my
programs. I used gr_bin_statistics_f as a template and designed a new
which uses the same method to callback to Python code and retune the

Now, I could get into more details of my specific program, however it
like this bug could be hard to replicate on different hardware. I am not
sure to the extent of the issue, but I know where the problem is.

The problem occurs in the callback code in gr_feval.i. As described in
bug report, Py_GILState_Ensure() is called before calleval(), and then
Py_GILState_Release() is called after returning from Python land. It is
this point that I get a segmentation fault.

For a gdb stacktrace similar to that on the bug report, please refer to
blog post:

After googling around for a while I read about similar issues which were
solved by adding a call to PyEval_InitThreads() right before
Py_GILState_Ensure() is called (hinted at in the bug report). This did
trick for me! Calling PyEval_InitThreads() acquires and initializes the
and calling it multiple times is a NOOP. More details can be found in
documentation. I am not sure if this is the correct solution, but it
for me. Others have suggested to me that the module using the
Python extension should ‘import threading’ early to ensure that
PyEval_InitThreads is called.

Finally, here is the system I tested on:
Fedora 14 64-bit
Linux tjadesktop #1 SMP Mon Dec 20 21:14:22 UTC
2010 x86_64 x86_64 x86_64 GNU/Linux
Intel i5 760
USRP 1 w/ WBX d’board

I have attached a small patch file which includes my fix. I could submit
formal fix if that would help, but I would really just like to get some
feedback on the issue. What do you guys think?


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