[Python-Dev] head crashing

"Martin v. Löwis" martin at v.loewis.de
Tue May 1 21:07:26 CEST 2007

> 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)

This is also what I found.

> and thus is safe to use without the GIL.

but I got to a different conclusion. If it really goes through the
pymalloc pool (obmalloc), then it must hold the GIL while doing so.
obmalloc itself is not thread-safe, and relies on the GIL for

In release mode, PyMEM_FREE goes directly to free, which is thread-safe.


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