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"""This test checks for correct fork() behavior.
"""
import _imp as imp
import os
import signal
import sys
import threading
import time
import unittest
from test.fork_wait import ForkWait
from test.support import (reap_children, get_attribute,
import_module, verbose)
# Skip test if fork does not exist.
get_attribute(os, 'fork')
class ForkTest(ForkWait):
def wait_impl(self, cpid):
deadline = time.monotonic() + 10.0
while time.monotonic() <= deadline:
# waitpid() shouldn't hang, but some of the buildbots seem to hang
# in the forking tests. This is an attempt to fix the problem.
spid, status = os.waitpid(cpid, os.WNOHANG)
if spid == cpid:
break
time.sleep(0.1)
self.assertEqual(spid, cpid)
self.assertEqual(status, 0, "cause = %d, exit = %d" % (status&0xff, status>>8))
def test_threaded_import_lock_fork(self):
"""Check fork() in main thread works while a subthread is doing an import"""
import_started = threading.Event()
fake_module_name = "fake test module"
partial_module = "partial"
complete_module = "complete"
def importer():
imp.acquire_lock()
sys.modules[fake_module_name] = partial_module
import_started.set()
time.sleep(0.01) # Give the other thread time to try and acquire.
sys.modules[fake_module_name] = complete_module
imp.release_lock()
t = threading.Thread(target=importer)
t.start()
import_started.wait()
pid = os.fork()
try:
# PyOS_BeforeFork should have waited for the import to complete
# before forking, so the child can recreate the import lock
# correctly, but also won't see a partially initialised module
if not pid:
m = __import__(fake_module_name)
if m == complete_module:
os._exit(0)
else:
if verbose > 1:
print("Child encountered partial module")
os._exit(1)
else:
t.join()
# Exitcode 1 means the child got a partial module (bad.) No
# exitcode (but a hang, which manifests as 'got pid 0')
# means the child deadlocked (also bad.)
self.wait_impl(pid)
finally:
try:
os.kill(pid, signal.SIGKILL)
except OSError:
pass
def test_nested_import_lock_fork(self):
"""Check fork() in main thread works while the main thread is doing an import"""
# Issue 9573: this used to trigger RuntimeError in the child process
def fork_with_import_lock(level):
release = 0
in_child = False
try:
try:
for i in range(level):
imp.acquire_lock()
release += 1
pid = os.fork()
in_child = not pid
finally:
for i in range(release):
imp.release_lock()
except RuntimeError:
if in_child:
if verbose > 1:
print("RuntimeError in child")
os._exit(1)
raise
if in_child:
os._exit(0)
self.wait_impl(pid)
# Check this works with various levels of nested
# import in the main thread
for level in range(5):
fork_with_import_lock(level)
def tearDownModule():
reap_children()
if __name__ == "__main__":
unittest.main()
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