New submission from gaborbernat <[email protected]>:
I've talked with Pablo about this in person, and as advised opening the issue
here now.
I've discovered that forked processes do not honour atexit registrations. See
the following example code:
from multiprocessing import Process, set_start_method
import time
import os
import atexit
def cleanup():
print(f"cleanup {os.getpid()}")
atexit.register(cleanup)
def run():
time.sleep(0.1)
print(f"process done {os.getpid()}")
# atexit._run_exitfuncs()
if __name__ == "__main__":
set_start_method("fork")
process = Process(target=run)
process.start()
process.join()
print("app finished")
In case of a forked process childs the atexit is never executed (note it works
if I ran them manually at the end of the child process; so they're registered
correctly). Switching to spawn method makes it work as expected. The behaviour
is the same even if you call register within the child process (as opposed to
being inherited during forking). Also found this StackOverflow question that
mentions this https://stackoverflow.com/a/26476585. At the very least the
documentation should explain this; though I'd expect atexit to be called before
finalization of the fork processes (assuming the child process exits with 0
exit code). d
----------
messages: 362197
nosy: davin, gaborbernat, pablogsal, pitrou
priority: normal
severity: normal
status: open
title: forked process in multiprocessing does not honour atexit
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Python tracker <[email protected]>
<https://bugs.python.org/issue39675>
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