[Numpy-discussion] minor threads-related issue in numpy-release 1.6.2 and numpy-dev

[Charles R Harris]

On Tue, Aug 14, 2012 at 7:47 AM, Aron Ahmadia <aron at ahmadia.net> wrote:

> Hi all,
>
> Installing numpy 1.6.2 against a Python interpreter built with the
> --without threads currently fails due to missing references
> to PyGILState_Ensure and PyGILState_Release.  The references appear to be
> coming from the following code in nditer.c.src:
>
> NPY_NO_EXPORT void
> NpyIter_DebugPrint(NpyIter *iter)
> {
> // <snip>
>     PyGILState_STATE gilstate = PyGILState_Ensure();
> // <snip>
>     PyGILState_Release(gilstate);
> }
>
> Since this is debugging code, I'm guessing it doesn't get called very
> frequently, and I could probably just #ifdef it out or use the NPY macros
> for grabbing the GIL for a non-threaded build: (NPY_ALLOW_C_API
> and NPY_DISABLE_C_API), but I don't understand why it's grabbing the GIL in
> the first place.  Where is it calling into the interpreter?  Does it need
> the GIL for something else?  I'm hesitant to touch this code and issue a
> pull request until I understand what it's trying to do.
>
> Heading on over to the master branch at numpy/numpy, I'm starting to
> notice more unprotected PyGILState references creeping into the development
> code.  Even the Python developers seem to think that nobody is using
> --without-threaded, so I'm not going to make a strong case for being more
> careful, but I do want to point it out in case you want to keep the numpy
> sources correct for this case.
>
>
Some parts of the numpy code release the GIL, so it needs to be reacquired
in order to call the Python C_API. A quick look shows a call to
PyObject_Print in the function and there may be other such calls. The right
fix is probably to use a couple of ifdefs if there is an easy way to
determine the Python interpreter configuration <looks>... WITH_THREAD seems
to be the right flag.

#ifdef WITH_THREAD
PyAPI_FUNC(void) PyThreadState_DeleteCurrent(void);
#endif

Could you give that a shot? TIA,
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