gh-90549: Fix leak of global named resources using multiprocessing spawn (GH-30617)

Co-authored-by: XD Trol <milestonejxd@gmail.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
(cherry picked from commit 30610d2837)

Co-authored-by: Leo Trol <milestone.jxd@gmail.com>

Lib/test/_test_multiprocessing.py

@@ -5,6 +5,7 @@
 import unittest
 import unittest.mock
 import queue as pyqueue
+import textwrap
 import time
 import io
 import itertools
@@ -5699,6 +5700,35 @@ class TestSyncManagerTypes(unittest.TestCase):
         self.run_worker(self._test_namespace, o)
 
 
+class TestNamedResource(unittest.TestCase):
+    def test_global_named_resource_spawn(self):
+        #
+        # gh-90549: Check that global named resources in main module
+        # will not leak by a subprocess, in spawn context.
+        #
+        testfn = os_helper.TESTFN
+        self.addCleanup(os_helper.unlink, testfn)
+        with open(testfn, 'w', encoding='utf-8') as f:
+            f.write(textwrap.dedent('''\
+                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(testfn)
+        # on error, err = 'UserWarning: resource_tracker: There appear to
+        # be 1 leaked semaphore objects to clean up at shutdown'
+        self.assertEqual(err, b'')
+
+
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
         # Just make sure names in not_exported are excluded