https://github.com/python/cpython/commit/e20863f2239950ca5e316a3ffab9f60abb1b5f48 commit: e20863f2239950ca5e316a3ffab9f60abb1b5f48 branch: 3.13 author: Miss Islington (bot) <[email protected]> committer: gpshead <[email protected]> date: 2025-12-24T03:03:47Z summary:
[3.13] gh-109263: Start process from spawn context in multiprocessing no longer have side effect (GH-135813) (#143116) gh-109263: Start process from spawn context in multiprocessing no longer have side effect (GH-135813) (cherry picked from commit c2202a7e661d40b1837cc0109cdb9ab40ec4e486) Co-authored-by: AN Long <[email protected]> files: A Misc/NEWS.d/next/Library/2025-06-22-18-57-19.gh-issue-109263.f92V95.rst M Lib/multiprocessing/spawn.py M Lib/test/_test_multiprocessing.py diff --git a/Lib/multiprocessing/spawn.py b/Lib/multiprocessing/spawn.py index daac1ecc34b55e..d43864c939cb63 100644 --- a/Lib/multiprocessing/spawn.py +++ b/Lib/multiprocessing/spawn.py @@ -184,7 +184,7 @@ def get_preparation_data(name): sys_argv=sys.argv, orig_dir=process.ORIGINAL_DIR, dir=os.getcwd(), - start_method=get_start_method(), + start_method=get_start_method(allow_none=True), ) # Figure out whether to initialise main in the subprocess as a module diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py index 7b46e4297c1503..08555f1693a7ba 100644 --- a/Lib/test/_test_multiprocessing.py +++ b/Lib/test/_test_multiprocessing.py @@ -5689,6 +5689,25 @@ def test_context(self): self.assertRaises(ValueError, ctx.set_start_method, None) self.check_context(ctx) + @staticmethod + def _dummy_func(): + pass + + def test_spawn_dont_set_context(self): + # Run a process with spawn or forkserver context may change + # the global start method, see gh-109263. + for method in ('fork', 'spawn', 'forkserver'): + multiprocessing.set_start_method(None, force=True) + + try: + ctx = multiprocessing.get_context(method) + except ValueError: + continue + process = ctx.Process(target=self._dummy_func) + process.start() + process.join() + self.assertIsNone(multiprocessing.get_start_method(allow_none=True)) + def test_context_check_module_types(self): try: ctx = multiprocessing.get_context('forkserver') diff --git a/Misc/NEWS.d/next/Library/2025-06-22-18-57-19.gh-issue-109263.f92V95.rst b/Misc/NEWS.d/next/Library/2025-06-22-18-57-19.gh-issue-109263.f92V95.rst new file mode 100644 index 00000000000000..6b96b5b9b2a0de --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-06-22-18-57-19.gh-issue-109263.f92V95.rst @@ -0,0 +1,2 @@ +Starting a process from spawn context in :mod:`multiprocessing` no longer +sets the start method globally. _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
