bpo-46391: Library multiprocess leaks named resources.

XD Trol · Trol · commit f202fff5a5a4 · 2022-06-07T22:35:46.000+08:00
diff --git a/Lib/multiprocessing/context.py b/Lib/multiprocessing/context.py
@@ -223,6 +223,10 @@ class Process(process.BaseProcess):
     def _Popen(process_obj):
         return _default_context.get_context().Process._Popen(process_obj)
 
+    @staticmethod
+    def _after_fork():
+        return _default_context.get_context().Process._after_fork()
+
 class DefaultContext(BaseContext):
     Process = Process
 
@@ -283,6 +287,11 @@ def _Popen(process_obj):
             from .popen_spawn_posix import Popen
             return Popen(process_obj)
 
+        @staticmethod
+        def _after_fork():
+            # process is spawned, nothing to do
+            pass
+
     class ForkServerProcess(process.BaseProcess):
         _start_method = 'forkserver'
         @staticmethod
@@ -326,6 +335,11 @@ def _Popen(process_obj):
             from .popen_spawn_win32 import Popen
             return Popen(process_obj)
 
+        @staticmethod
+        def _after_fork():
+            # process is spawned, nothing to do
+            pass
+
     class SpawnContext(BaseContext):
         _name = 'spawn'
         Process = SpawnProcess
diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py
@@ -304,8 +304,7 @@ def _bootstrap(self, parent_sentinel=None):
             if threading._HAVE_THREAD_NATIVE_ID:
                 threading.main_thread()._set_native_id()
             try:
-                util._finalizer_registry.clear()
-                util._run_after_forkers()
+                self._after_fork()
             finally:
                 # delay finalization of the old process object until after
                 # _run_after_forkers() is executed
@@ -336,6 +335,13 @@ def _bootstrap(self, parent_sentinel=None):
 
         return exitcode
 
+    @staticmethod
+    def _after_fork():
+        from . import util
+        util._finalizer_registry.clear()
+        util._run_after_forkers()
+
+
 #
 # We subclass bytes to avoid accidental transmission of auth keys over network
 #
diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
@@ -5760,6 +5760,33 @@ def test_namespace(self):
         self.run_worker(self._test_namespace, o)
 
 
+class TestNamedResource(unittest.TestCase):
+    def test_global_named_resource_spawn(self):
+        #
+        # Check that global named resources in main module
+        # will not leak by a subprocess, in spawn context.
+        #
+        with os_helper.temp_dir() as tmp_dir:
+            source = os.path.join(tmp_dir, 'source.py')
+            with open(source, 'w') as f:
+                f.write('''if 1:
+                    import multiprocessing as mp
+
+                    ctx = mp.get_context('spawn')
+
+                    global_resource = ctx.Semaphore()
+
+                    def submain(): pass
+
+                    if __name__ == '__main__':
+                        p = ctx.Process(target=submain)
+                        p.start()
+                        p.join()
+                ''')
+            rc, out, err = test.support.script_helper.assert_python_ok(source)
+            self.assertNotRegex(err, b'resource_tracker: There appear to be .* leaked')
+
+
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
         # Just make sure names in not_exported are excluded
diff --git a/Misc/NEWS.d/next/Library/2022-01-16-03-09-58.bpo-46391.LZUzDI.rst b/Misc/NEWS.d/next/Library/2022-01-16-03-09-58.bpo-46391.LZUzDI.rst
@@ -0,0 +1,2 @@
+Fix that Library multiprocess leaks named resources when global named
+resources are used in the main module in spawn context.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Fix that Library multiprocess leaks named resources when global named`
	`2`	`+resources are used in the main module in spawn context.`