On Tue, Apr 21, 2020 at 10:49 AM Antoine Pitrou
On Tue, 21 Apr 2020 18:46:04 +0200 Petr Viktorin
On 2020-04-21 11:01, Antoine Pitrou wrote:
On Mon, 20 Apr 2020 19:21:21 -0600 Eric Snow
Honest question: how many C extensions have process-global state that will cause problems under subinterpreters? In other words, how many already break in mod_wsgi?
A slightly tricky question is what happens if a PyObject survives longer than the subinterpreter that created it.
For example, in PyArrow, we allow passing a Python buffer-like object as a C++ buffer to C++ APIs. The C++ buffer could conceivably be kept around by C++ code for some time. When the C++ buffer is destroyed, Py_DECREF() is called on the Python object (I figure that we would have to switch to the future interpreter-aware PyGILState API -- when will it be available?).
In this scenario given that the PyObject owning the buffer passed to C++ by PyArrow was Py_INCREF'd, an option during Py_Finalize is to not release anything who's refcount never made it to 0. Which also implies leaving enough of the interpreter state around so that Py_DECREF could be called and trigger the free(). Basically (sub)interpreter finalization should have the right to return failure. Everything ever allocated by an interpreter holds a reference (implied today) to its associated interpreter state. -gps
But what happens if the interpreter which created the Python object is already destroyed at this point?
That's a good question. What happens today if someone calls Py_Finalize while the buffer is still around?
I don't think you need to treat *sub*interpreters specially.
The difference is that subinterpreters may have a shorter lifetime than the main interpreter. Also, we're currently using a global memory allocator, so simple operations may work until the process dies.
_______________________________________________ Python-Dev mailing list -- firstname.lastname@example.org To unsubscribe send an email to email@example.com https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://firstname.lastname@example.org/message/UWWO3RS3... Code of Conduct: http://python.org/psf/codeofconduct/