From 5f2ab582312f0e26848aaa2ba2c1c318a2d78b6f Mon Sep 17 00:00:00 2001 From: Antoine Pitrou Date: Wed, 28 Jun 2017 12:29:08 +0200 Subject: [PATCH] [3.5] Clear potential ref cycle between Process and Process target (GH-2470) * Clear potential ref cycle between Process and Process target Besides Process.join() not being called, this was an indirect cause of bpo-30775. The threading module already does this. * Add issue reference. (cherry picked from commit 79d37ae979a65ada0b2ac820279ccc3b1cd41ba6) --- Lib/multiprocessing/process.py | 3 +++ Lib/test/_test_multiprocessing.py | 18 ++++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py index bca8b7a0047070..f9c22703df29cb 100644 --- a/Lib/multiprocessing/process.py +++ b/Lib/multiprocessing/process.py @@ -104,6 +104,9 @@ def start(self): _cleanup() self._popen = self._Popen(self) self._sentinel = self._popen.sentinel + # 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 _children.add(self) def terminate(self): diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py index 76209f134330a1..b9cd86e984e701 100644 --- a/Lib/test/_test_multiprocessing.py +++ b/Lib/test/_test_multiprocessing.py @@ -191,6 +191,12 @@ def get_value(self): # Testcases # +class DummyCallable: + def __call__(self, q, c): + assert isinstance(c, DummyCallable) + q.put(5) + + class _TestProcess(BaseTestCase): ALLOWED_TYPES = ('processes', 'threads') @@ -398,6 +404,18 @@ def test_sentinel(self): p.join() self.assertTrue(wait_for_handle(sentinel, timeout=1)) + 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) + + # # #