[New-bugs-announce] [issue4200] atexit module not safe in Python 3.0 with multiple interpreters
report at bugs.python.org
Sat Oct 25 00:45:55 CEST 2008
New submission from Graham Dumpleton <Graham.Dumpleton at gmail.com>:
In Python 3.0 the atexit module was translated from Python code to C code.
Prior to Python 3.0, because it was implemented at C code level, the list of
callbacks was specific to each sub interpreter. In Python 3.0 that appears to
no longer be the case, with the list of callbacks being maintained globally as
static C variable across all interpreters.
The end result is that if a sub interpreter registers an atexit callback, that
callback will be called within the context of the main interpreter on call of
Py_Finalize(), and not in context of the sub interpreter against which it was
Various problems could ensue from this depending on whether or not the sub
interpreter had also since been destroyed.
Still need to validate the above, but from visual inspection looks to be a
problem. Issue found because mod_wsgi will trigger atexit callbacks for a sub
interpreter when the sub interpreter is being destroyed. This is because Python
prior to 3.0 only did it from the main interpreter. In Python 3.0, this all
seems to get messed up now as no isolation between callbacks for each
For mod_wsgi case, since it is explicitly triggering atexit callbacks for sub
interpreter, in doing so it is actually calling all registered atexit callbacks
across all interpreters for each sub interpreter being destroyed. They then
again get called for Py_Finalize().
Even if mod_wsgi weren't doing this, still a problem that Py_Finalize() calling
atexit callbacks in context of main interpreter which were actually associated
with sub interpreter.
For mod_wsgi, will probably end up installing own 'atexit' module variant in
sub interpreters to ensure separation.
components: Interpreter Core
title: atexit module not safe in Python 3.0 with multiple interpreters
versions: Python 3.0
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