diff options
| -rw-r--r-- | Lib/multiprocessing/synchronize.py | 9 | ||||
| -rw-r--r-- | Lib/test/_test_multiprocessing.py | 22 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Core and Builtins/2023-07-25-22-35-35.gh-issue-77377.EHAbXx.rst | 1 |
3 files changed, 30 insertions, 2 deletions
diff --git a/Lib/multiprocessing/synchronize.py b/Lib/multiprocessing/synchronize.py index 42624b5..2328d33 100644 --- a/Lib/multiprocessing/synchronize.py +++ b/Lib/multiprocessing/synchronize.py @@ -50,8 +50,8 @@ class SemLock(object): def __init__(self, kind, value, maxvalue, *, ctx): if ctx is None: ctx = context._default_context.get_context() - name = ctx.get_start_method() - unlink_now = sys.platform == 'win32' or name == 'fork' + self.is_fork_ctx = ctx.get_start_method() == 'fork' + unlink_now = sys.platform == 'win32' or self.is_fork_ctx for i in range(100): try: sl = self._semlock = _multiprocessing.SemLock( @@ -103,6 +103,11 @@ class SemLock(object): if sys.platform == 'win32': h = context.get_spawning_popen().duplicate_for_child(sl.handle) else: + if self.is_fork_ctx: + raise RuntimeError('A SemLock created in a fork context is being ' + 'shared with a process in a spawn context. This is ' + 'not supported. Please use the same context to create ' + 'multiprocessing objects and Process.') h = sl.handle return (h, sl.kind, sl.maxvalue, sl.name) diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py index 29dc386..9bc8242 100644 --- a/Lib/test/_test_multiprocessing.py +++ b/Lib/test/_test_multiprocessing.py @@ -5345,6 +5345,28 @@ class TestStartMethod(unittest.TestCase): print(err) self.fail("failed spawning forkserver or grandchild") + @unittest.skipIf(sys.platform == "win32", + "Only Spawn on windows so no risk of mixing") + @only_run_in_spawn_testsuite("avoids redundant testing.") + def test_mixed_startmethod(self): + # Fork-based locks cannot be used with spawned process + for process_method in ["spawn", "forkserver"]: + queue = multiprocessing.get_context("fork").Queue() + process_ctx = multiprocessing.get_context(process_method) + p = process_ctx.Process(target=close_queue, args=(queue,)) + err_msg = "A SemLock created in a fork" + with self.assertRaisesRegex(RuntimeError, err_msg): + p.start() + + # non-fork-based locks can be used with all other start methods + for queue_method in ["spawn", "forkserver"]: + for process_method in multiprocessing.get_all_start_methods(): + queue = multiprocessing.get_context(queue_method).Queue() + process_ctx = multiprocessing.get_context(process_method) + p = process_ctx.Process(target=close_queue, args=(queue,)) + p.start() + p.join() + @unittest.skipIf(sys.platform == "win32", "test semantics don't make sense on Windows") diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-07-25-22-35-35.gh-issue-77377.EHAbXx.rst b/Misc/NEWS.d/next/Core and Builtins/2023-07-25-22-35-35.gh-issue-77377.EHAbXx.rst new file mode 100644 index 0000000..194851d --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2023-07-25-22-35-35.gh-issue-77377.EHAbXx.rst @@ -0,0 +1 @@ +Ensure that multiprocessing synchronization objects created in a fork context are not sent to a different process created in a spawn context. This changes a segfault into an actionable RuntimeError in the parent process. |