Olivier Grisel added the comment:
I can wait (or monkey-patch the stuff I need as a temporary workaround in my
code). My worry is that Python 3.4 will introduce a new feature that is very
crash-prone.
Take this simple program that uses the newly introduced `get_context` function
(the same problem happens with `set_start_method`):
filename: mytool
"""
#!/usr/bin/env python
from multiprocessing import freeze_support, get_context
def compute_stuff(i):
# in real life you could use a lib that uses threads
# like cuda and that would crash with the default 'fork'
# mode under POSIX
return i ** 2
if __name__ == "__main__":
freeze_support()
ctx = get_context('spawn')
ctx.Pool(4).map(compute_stuff, range(8))
"""
If you chmod +x this file and run it with ./mytool, the user will get an
infinitely running process that keeps displaying on stderr:
"""
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 96, in
spawn_main
exitcode = _main(fd)
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 105, in
_main
prepare(preparation_data)
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 210, in
prepare
import_main_path(data['main_path'])
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 256, in
import_main_path
raise ImportError(name=main_name)
ImportError
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 96, in
spawn_main
exitcode = _main(fd)
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 105, in
_main
prepare(preparation_data)
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 210, in
prepare
import_main_path(data['main_path'])
File "/opt/Python-HEAD/lib/python3.4/multiprocessing/spawn.py", line 256, in
import_main_path
raise ImportError(name=main_name)
ImportError
...
"""
until the user kills the process. Is there really nothing we can do to avoid
releasing Python 3.4 with this bug?
----------
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<http://bugs.python.org/issue19946>
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