bpo-40550: Fix time-of-check/time-of-action issue in subprocess.Popen.send_signal. (GH-20010)

send_signal() now swallows the exception if the process it thought was still alive winds up not to exist anymore (always a plausible race condition despite the checks).

Co-authored-by: Gregory P. Smith <greg@krypto.org>
This commit is contained in:
Filipe Laíns 2020-11-21 09:22:08 +00:00 committed by GitHub
parent 31729366e2
commit 01a202ab6b
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3 changed files with 19 additions and 1 deletions

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@ -2078,7 +2078,11 @@ class Popen(object):
# The race condition can still happen if the race condition
# described above happens between the returncode test
# and the kill() call.
os.kill(self.pid, sig)
try:
os.kill(self.pid, sig)
except ProcessLookupError:
# Supress the race condition error; bpo-40550.
pass
def terminate(self):
"""Terminate the process with SIGTERM

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@ -3229,6 +3229,19 @@ class POSIXProcessTestCase(BaseTestCase):
# so Popen failed to read it and uses a default returncode instead.
self.assertIsNotNone(proc.returncode)
def test_send_signal_race2(self):
# bpo-40550: the process might exist between the returncode check and
# the kill operation
p = subprocess.Popen([sys.executable, '-c', 'exit(1)'])
# wait for process to exit
while not p.returncode:
p.poll()
with mock.patch.object(p, 'poll', new=lambda: None):
p.returncode = None
p.send_signal(signal.SIGTERM)
def test_communicate_repeated_call_after_stdout_close(self):
proc = subprocess.Popen([sys.executable, '-c',
'import os, time; os.close(1), time.sleep(2)'],

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@ -0,0 +1 @@
Fix time-of-check/time-of-action issue in subprocess.Popen.send_signal.