From c6b20be85c0de6f2355c67ae6e7e578941275cc0 Mon Sep 17 00:00:00 2001 From: Jake Tesler Date: Tue, 19 Nov 2019 11:50:12 -0800 Subject: bpo-38707: Fix for multiprocessing.Process MainThread.native_id (GH-17088) 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 The resulting behavior is such that the new process' `MainThread` captures an incorrect/outdated `native_id` (the parent's instead of its own).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 --- Lib/multiprocessing/process.py | 2 ++ Lib/test/_test_multiprocessing.py | 22 ++++++++++++++++++++++ .../2019-11-08-00-36-10.bpo-38707.SZL036.rst | 1 + 3 files changed, 25 insertions(+) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2019-11-08-00-36-10.bpo-38707.SZL036.rst diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py index c62c826..be13c07 100644 --- a/Lib/multiprocessing/process.py +++ b/Lib/multiprocessing/process.py @@ -301,6 +301,8 @@ class BaseProcess(object): _current_process = self _parent_process = _ParentProcess( self._parent_name, self._parent_pid, parent_sentinel) + if threading._HAVE_THREAD_NATIVE_ID: + threading.main_thread()._set_native_id() try: util._finalizer_registry.clear() util._run_after_forkers() diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py index f7bebc6..611291c 100644 --- a/Lib/test/_test_multiprocessing.py +++ b/Lib/test/_test_multiprocessing.py @@ -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) diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-11-08-00-36-10.bpo-38707.SZL036.rst b/Misc/NEWS.d/next/Core and Builtins/2019-11-08-00-36-10.bpo-38707.SZL036.rst new file mode 100644 index 0000000..4ef9ed8 --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2019-11-08-00-36-10.bpo-38707.SZL036.rst @@ -0,0 +1 @@ +``MainThread.native_id`` is now correctly reset in child processes spawned using :class:`multiprocessing.Process`, instead of retaining the parent's value. -- cgit v0.12