New submission from Markus Mohrhard <mark...@dug.com>:
We have hit an issue in the pickle module where the code throws an exception in
a threaded environment:
The interesting piece of the backtrace is:
File "/xxx/1004060/lib/python3.7/site-packages/numpy/core/__init__.py", line
130, in _ufunc_reduce
return _ufunc_reconstruct, (whichmodule(func, name), name)
File "/xxx/lib/python3.7/pickle.py", line 309, in whichmodule
for module_name, module in list(sys.modules.items()):
RuntimeError: dictionary changed size during iteration
I tried to find a code path that would explain how the dict could be changed
while the list is created but have not been able to find a code path that
releases the GIL.
The executable is using many threads with imports happening in random threads
and a custom class loader but we already make sure that the class loader is
always holding the GIL.
The issue happens quite rarely (maybe once every one thousand's execution) so I
don't have a reproducer right now.
----------
components: Extension Modules
messages: 366762
nosy: Markus Mohrhard
priority: normal
severity: normal
status: open
title: list(sys.modules.items()) can throw RuntimeError: dictionary changed
size during iteration
type: behavior
versions: Python 3.7
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue40327>
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