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bpo-38707: Fix for multiprocessing.Process MainThread.native_id (GH-17088)

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This PR implements a fix for `multiprocessing.Process` objects; the error occurs when Processes are created using either `fork` or `forkserver` as the `start_method`.

In these instances, the `MainThread` of the newly created `Process` object retains all attributes from its parent's `MainThread` object, including the `native_id` attribute. The resulting behavior is such that the new process' `MainThread` captures an incorrect/outdated `native_id` (the parent's instead of its own). 

This change forces the Process object to update its `native_id` attribute during the bootstrap process.

cc @vstinner





https://bugs.python.org/issue38707



Automerge-Triggered-By: @pitrou
This commit is contained in:
Jake Tesler 2019-11-19 11:50:12 -08:00 • committed by Miss Islington (bot)
parent 892221bfa0
commit c6b20be85c
3 changed files with 25 additions and 0 deletions
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22
Lib/test/_test_multiprocessing.py
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@ -361,6 +361,28 @@ class _TestProcess(BaseTestCase):
self.assertNotIn(p, self.active_children())
close_queue(q)
@unittest.skipUnless(threading._HAVE_THREAD_NATIVE_ID, "needs native_id")
def test_process_mainthread_native_id(self):
if self.TYPE == 'threads':
self.skipTest('test not appropriate for {}'.format(self.TYPE))
current_mainthread_native_id = threading.main_thread().native_id
q = self.Queue(1)
p = self.Process(target=self._test_process_mainthread_native_id, args=(q,))
p.start()
child_mainthread_native_id = q.get()
p.join()
close_queue(q)
self.assertNotEqual(current_mainthread_native_id, child_mainthread_native_id)
@classmethod
def _test_process_mainthread_native_id(cls, q):
mainthread_native_id = threading.main_thread().native_id
q.put(mainthread_native_id)
@classmethod
def _sleep_some(cls):
time.sleep(100)