New submission from Olivier Grisel:
Here is a simple python program that uses the new forkserver feature introduced
in 3.4b1:
name: checkforkserver.py
"""
import multiprocessing
import os
def do(i):
print(i, os.getpid())
def test_forkserver():
mp = multiprocessing.get_context('forkserver')
mp.Pool(2).map(do, range(3))
if __name__ == "__main__":
test_forkserver()
"""
When running this using the "python check_forkserver.py" command everything
works as expected.
When running this using the nosetests launcher ("nosetests -s
check_forkserver.py"), I get:
"""
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/forkserver.py", line
141, in main
spawn.import_main_path(main_path)
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 252, in
import_main_path
methods.init_module_attrs(main_module)
File "<frozen importlib._bootstrap>", line 1051, in init_module_attrs
AttributeError: 'NoneType' object has no attribute 'loader'
"""
Indeed, the spec variable in multiprocessing/spawn.py's import_main_path
function is None as the nosetests script is not a regular python module: in
particular is does not have a ".py" extension.
If I copy or symlink or renamed the "nosetests" script as "nosetests.py" in the
same folder, this works as expected. I am not familiar enough with the
importlib machinery to suggest a fix for this bug.
Also there is a typo in the comment: "causing a psuedo fork bomb" => "causing a
pseudo fork bomb".
Note: I am running CPython head updated today.
----------
components: Library (Lib)
messages: 205810
nosy: Olivier.Grisel
priority: normal
severity: normal
status: open
title: multiprocessing crash with forkserver or spawn when run from a non
".py" ending script
versions: Python 3.4
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue19946>
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