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[2.7] bpo-30775: Clear potential ref cycle between Process and Process target (GH-2470) #2473

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Merged
vstinner merged 1 commit into from
Jun 28, 2017
Merged

[2.7] bpo-30775: Clear potential ref cycle between Process and Process target (GH-2470) #2473

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3 changes: 3 additions & 0 deletions Lib/multiprocessing/process.py
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Original file line number Diff line number Diff line change
Expand Up @@ -128,6 +128,9 @@ def start(self):
else:
from .forking import Popen
self._popen = Popen(self)
# Avoid a refcycle if the target function holds an indirect
# reference to the process object (see bpo-30775)
del self._target, self._args, self._kwargs
_current_process._children.add(self)

def terminate(self):
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18 changes: 18 additions & 0 deletions Lib/test/test_multiprocessing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -175,6 +175,12 @@ def get_value(self):
# Testcases
#

class DummyCallable(object):
def __call__(self, q, c):
assert isinstance(c, DummyCallable)
q.put(5)


class _TestProcess(BaseTestCase):

ALLOWED_TYPES = ('processes', 'threads')
Expand Down Expand Up @@ -355,6 +361,18 @@ def test_sys_exit(self):
p.join(5)
self.assertEqual(p.exitcode, reason)

def test_lose_target_ref(self):
c = DummyCallable()
wr = weakref.ref(c)
q = self.Queue()
p = self.Process(target=c, args=(q, c))
del c
p.start()
p.join()
self.assertIs(wr(), None)
self.assertEqual(q.get(), 5)


#
#
#
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