gh-82300: Add track parameter to multiprocessing.shared_memory (#110778)

Add a track parameter to shared memory to allow resource tracking via the side-launched resource tracker process to be disabled on platforms that use it (POSIX).

This allows people who do not want automated cleanup at process exit because they are using the shared memory with processes not participating in Python's resource tracking to use the shared_memory API.

Co-authored-by: Łukasz Langa <lukasz@langa.pl>
Co-authored-by: Guido van Rossum <gvanrossum@gmail.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Co-authored-by: Gregory P. Smith <greg@krypto.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index ec003d8dc43..a94eb6c0ae4 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -4455,6 +4455,59 @@ class _TestSharedMemory(BaseTestCase):
                     "resource_tracker: There appear to be 1 leaked "
                     "shared_memory objects to clean up at shutdown", err)
 
+    @unittest.skipIf(os.name != "posix", "resource_tracker is posix only")
+    def test_shared_memory_untracking(self):
+        # gh-82300: When a separate Python process accesses shared memory
+        # with track=False, it must not cause the memory to be deleted
+        # when terminating.
+        cmd = '''if 1:
+            import sys
+            from multiprocessing.shared_memory import SharedMemory
+            mem = SharedMemory(create=False, name=sys.argv[1], track=False)
+            mem.close()
+        '''
+        mem = shared_memory.SharedMemory(create=True, size=10)
+        # The resource tracker shares pipes with the subprocess, and so
+        # err existing means that the tracker process has terminated now.
+        try:
+            rc, out, err = script_helper.assert_python_ok("-c", cmd, mem.name)
+            self.assertNotIn(b"resource_tracker", err)
+            self.assertEqual(rc, 0)
+            mem2 = shared_memory.SharedMemory(create=False, name=mem.name)
+            mem2.close()
+        finally:
+            try:
+                mem.unlink()
+            except OSError:
+                pass
+            mem.close()
+
+    @unittest.skipIf(os.name != "posix", "resource_tracker is posix only")
+    def test_shared_memory_tracking(self):
+        # gh-82300: When a separate Python process accesses shared memory
+        # with track=True, it must cause the memory to be deleted when
+        # terminating.
+        cmd = '''if 1:
+            import sys
+            from multiprocessing.shared_memory import SharedMemory
+            mem = SharedMemory(create=False, name=sys.argv[1], track=True)
+            mem.close()
+        '''
+        mem = shared_memory.SharedMemory(create=True, size=10)
+        try:
+            rc, out, err = script_helper.assert_python_ok("-c", cmd, mem.name)
+            self.assertEqual(rc, 0)
+            self.assertIn(
+                b"resource_tracker: There appear to be 1 leaked "
+                b"shared_memory objects to clean up at shutdown", err)
+        finally:
+            try:
+                mem.unlink()
+            except OSError:
+                pass
+            resource_tracker.unregister(mem._name, "shared_memory")
+            mem.close()
+
 #
 # Test to verify that `Finalize` works.
 #