`gevent` execmode hangs in python 3.7.5

The problem only occurs at python3.

Environment:

• OS: Linux faa410b1f09b 4.19.121-linuxkit #1 SMP Thu Jan 21 15:36:34 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
• Python version: Python 3.7.5

Dependencies:

apipkg         1.5
attrs          20.3.0
execnet        1.8.0
gevent         21.1.2
greenlet       1.0.0
iniconfig      1.1.1
packaging      20.9
pip            19.2.3
pluggy         0.13.1
py             1.10.0
pyparsing      2.4.7
pytest         6.2.3
pytest-forked  1.3.0
pytest-xdist   2.2.1
setuptools     41.2.0
toml           0.10.2
zope.event     4.5.0
zope.interface 5.4.0

Command: pytest -d --tx popen//execmodel=gevent test.py

Code:

from gevent import monkey
monkey.patch_all()


def test_assert_0():
    assert 0


def test_assert_1():
    assert 1

In Python 2 environment command runs all tests, reports failure on test_assert_0 and ends. In Python 3 environment test hangs before scanning for tests.

Execnet debug logs:

====================================== test session starts =======================================
platform darwin -- Python 3.8.2, pytest-6.2.3, py-1.10.0, pluggy-0.13.1
rootdir: /Users/changwan.park/Documents/py3_venv
plugins: xdist-2.2.1, forked-1.3.0
gw0 C[13946] gw0 [receiver-thread] RECEIVERTHREAD: starting to run
[13946] gw0 sent <Message CHANNEL_EXEC channel=1 lendata=8631>
[13946] gw0 sent <Message CHANNEL_DATA channel=1 lendata=470>
[13948] creating workergateway on <execnet.gateway_base.Popen2IO object at 0x10dc89bb0>
[13948] gw0-worker [serve] spawning receiver thread
[13948] gw0-worker [serve] joining receiver thread
[13948] gw0-worker waiting for receiver thread to finish
[13948] gw0-worker [receiver-thread] RECEIVERTHREAD: starting to run
[13948] gw0-worker [receiver-thread] received <Message CHANNEL_EXEC channel=1 lendata=8631>
[13948] gw0-worker [receiver-thread] received <Message CHANNEL_DATA channel=1 lendata=470>

Different issue compared with https://github.com/pytest-dev/execnet/issues/75. By comparing execnet debug trace, above example hangs after gw0-worker only receives gw0but does not execute the received command.

After some digging, I found out the hanging occurres since remote_exec hangs. See https://github.com/pytest-dev/execnet/issues/123.

Reproduisez le problème avec la commande pytest indiquée et test.py sous Python 3.7.5, puis comparez la trace de débogage execnet avec le comportement de Python 2. Commencez par lire l’issue execnet remote_exec référencée et le chemin gevent execmode ; le travail est terminé lorsque la commande ne reste plus bloquée avant la collecte des tests et signale l’assertion en échec attendue.