ptvsd hangs on subprocess.Process.join

[sjdv1982]

Environment data

• PTVSD version: /extensions/ms-python.python-2018.10.1
• OS and version: Ubuntu 18.04.1
• Python version (& distribution if applicable, e.g. Anaconda):
  Python 3.6.6, Anaconda 2.7.13, Python 2.7.16
• Using VS Code or Visual Studio: VS Code

Actual behavior

Subprocess code gets never executed
Subprocess remains alive after 5 seconds
On Python2, the debugged main process never terminates either

Expected behavior

Subprocess code to be executed and to terminate immediately
This happens for all three Python versions if the entire code is executed directly

Steps to reproduce:

from multiprocessing import Process

def run():
    print("RUN")

p = Process(target=run)
p.start()
print("JOIN")
p.join(5.0)  # wait for 5 secs to let the process finish
print(p.is_alive())  # should be False

[int19h]

If you do this:

from multiprocessing import Process

def run():
    print("RUN")

if __name__ == "__main__":
    multiprocessing.set_start_method('spawn')  # note this line
    p = Process(target=run)
    p.start()
    print("JOIN")
    p.join(5.0)  # wait for 5 secs to let the process finish
    print(p.is_alive())  # should be False

Does it work for you on 3.6?

(Note that the __main__ thing is necessary in any case if your want your code to be portable to Windows.)

[sjdv1982]

That works, thanks! But doesn't that disable CoW on Linux?

…

On Mon, Nov 19, 2018 at 4:11 PM Pavel Minaev ***@***.***> wrote: If you do this: from multiprocessing import Process def run(): print("RUN") if __name__ == "__main__": multiprocessing.set_start_method('spawn') # note this line p = Process(target=run) p.start() print("JOIN") p.join(5.0) # wait for 5 secs to let the process finish print(p.is_alive()) # should be False Does it work for you on 3.6? (Note that the __main__ thing is necessary in any case if your want your code to be portable to Windows.) — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1036 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AHpXsUz2WmYB2dttqSs8oFbsg0fQfnvGks5uwsoegaJpZM4YpLm7> .

[int19h]

It disables fork altogether. When multiprocessing operates in this mode, no data is shared across processes at all, except what you pass as arguments to the function.

We don't support multiprocessing with fork currently - #943 tracks this feature, so I'll close this one as a dupe.