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Tue May 1 20:17:53 CEST 2007 · https://mail.python.org/pipermail/python-dev/2007-May/072911.html

On 5/1/07, Neal Norwitz <nnorwitz at gmail.com> wrote:
>
> In rev 54982 (the first time this crash was seen), I see something
> which might create a problem.  In python/trunk/Modules/posixmodule.c
> (near line 6300):
>
> +       PyMem_FREE(mode);
>        Py_END_ALLOW_THREADS

The PyMem_MALLOC call that creates 'mode' is also called without explicitly
holding the GIL.

Can you call PyMem_FREE() without the GIL held?  I couldn't find it
> documented either way.

I believe the GIL does not need to be held, but obviously Tim or someone
with more memory experience should step in to say definitively.

If you look at Include/pymem.h, PyMem_FREE gets defined as PyObject_FREE in
a debug build.  PyObject_Free is defined at _PyObject_DebugFree.  That
function checks that the memory has not been written with the debug bit
pattern and then calls PyObject_Free.  That call just sticks the memory back
into pymalloc's memory pool which is implemented without using any Python
objects.

In other words no Python objects are used in pymalloc (to my knowledge) and
thus is safe to use without the GIL.

-Brett
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