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bpo-33613, test_semaphore_tracker_sigint: fix race condition (#7850)

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Fail `test_semaphore_tracker_sigint` if no warnings are expected and one is received.

Fix race condition when the child receives SIGINT before it can register signal handlers for it.

The race condition occurs when the parent calls
`_semaphore_tracker.ensure_running()` (which in turn spawns the
semaphore_tracker using `_posixsubprocess.fork_exec`), the child
registers the signal handlers and the parent tries to kill the child.
What seem to happen is that in some slow systems, the parent sends the
signal to kill the child before the child protects against the signal.
This commit is contained in:
Pablo Galindo 2018-09-04 09:53:54 +01:00 • committed by Antoine Pitrou
parent e9ba3705de
commit ec74d187f5
3 changed files with 52 additions and 12 deletions
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27
Lib/test/_test_multiprocessing.py
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@ -20,6 +20,7 @@ import logging
import struct
import operator
import weakref
import warnings
import test.support
import test.support.script_helper
from test import support
@ -4517,17 +4518,19 @@ class TestSemaphoreTracker(unittest.TestCase):
# bpo-31310: if the semaphore tracker process has died, it should
# be restarted implicitly.
from multiprocessing.semaphore_tracker import _semaphore_tracker
_semaphore_tracker.ensure_running()
pid = _semaphore_tracker._pid
if pid is not None:
os.kill(pid, signal.SIGKILL)
os.waitpid(pid, 0)
with warnings.catch_warnings(record=True) as all_warn:
_semaphore_tracker.ensure_running()
pid = _semaphore_tracker._pid
os.kill(pid, signum)
time.sleep(1.0) # give it time to die
ctx = multiprocessing.get_context("spawn")
with contextlib.ExitStack() as stack:
if should_die:
stack.enter_context(self.assertWarnsRegex(
UserWarning,
"semaphore_tracker: process died"))
with warnings.catch_warnings(record=True) as all_warn:
sem = ctx.Semaphore()
sem.acquire()
sem.release()
@ -4537,11 +4540,23 @@ class TestSemaphoreTracker(unittest.TestCase):
del sem
gc.collect()
self.assertIsNone(wr())
if should_die:
self.assertEqual(len(all_warn), 1)
the_warn = all_warn[0]
issubclass(the_warn.category, UserWarning)
self.assertTrue("semaphore_tracker: process died"
in str(the_warn.message))
else:
self.assertEqual(len(all_warn), 0)
def test_semaphore_tracker_sigint(self):
# Catchable signal (ignored by semaphore tracker)
self.check_semaphore_tracker_death(signal.SIGINT, False)
def test_semaphore_tracker_sigterm(self):
# Catchable signal (ignored by semaphore tracker)
self.check_semaphore_tracker_death(signal.SIGTERM, False)
def test_semaphore_tracker_sigkill(self):
# Uncatchable signal.
self.check_semaphore_tracker_death(signal.SIGKILL, True)