python · vstinner · Jun 28, 2017 · Jun 28, 2017
diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py
@@ -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):

diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
@@ -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')
@@ -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)
+
+
 #
 #
 #