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Author vstinner
Recipients Batuhan Taskaya, vstinner
Date 2020-03-27.16:29:48
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <>
_at_fork() has a bug: it creates a _DummyThread instead of a _MainThread. Example:
import os, _thread, threading, time

def fork_in_thread():
    pid = os.fork()
    if pid:
        # parent

    # child process
    print(f"child process: {threading.current_thread()=}")
    print(f"child process: {threading._main_thread=}")

print(f"parent process: {threading.current_thread()=}")
print(f"parent process: {threading._main_thread=}")

_thread.start_new_thread(fork_in_thread, ())
# block the main thread: fork_in_thread() exit the process

parent process: threading.current_thread()=<_MainThread(MainThread, started 139879200077632)>
parent process: threading._main_thread=<_MainThread(MainThread, started 139879200077632)>
child process: threading.current_thread()=<_DummyThread(Dummy-1, started daemon 139878980245248)>
child process: threading._main_thread=<_DummyThread(Dummy-1, started daemon 139878980245248)>

My PR 19191 fix the issue:
parent process: threading.current_thread()=<_MainThread(MainThread, started 140583665170240)>
parent process: threading._main_thread=<_MainThread(MainThread, started 140583665170240)>
child process: threading.current_thread()=<_MainThread(MainThread, started 140583445075712)>
child process: threading._main_thread=<_MainThread(MainThread, started 140583445075712)>
Date User Action Args
2020-03-27 16:29:48vstinnersetrecipients: + vstinner, Batuhan Taskaya
2020-03-27 16:29:48vstinnersetmessageid: <>
2020-03-27 16:29:48vstinnerlinkissue40089 messages
2020-03-27 16:29:48vstinnercreate