Add a better test case.

Author: ZeroIntensity

Lib/test/test_free_threading/test_gc.py

@@ -62,6 +62,38 @@ def mutator_thread():
         with threading_helper.start_threads(gcs + mutators):
             pass
 
+    def test_freeze_object_in_brc_queue(self):
+        # GH-142975: Freezing objects in the BRC queue could result in some
+        # objects having a zero refcount without being deallocated.
+
+        class Weird:
+            # We need a destructor to trigger the check for object resurrection
+            def __del__(self):
+                pass
+
+        # This is owned by the main thread, so the subthread will have to increment
+        # this object's reference count.
+        weird = Weird()
+
+        def evil():
+            gc.freeze()
+
+            # Decrement the reference count from this thread, which will trigger the
+            # slow path during resurrection and add our weird object to the BRC queue.
+            nonlocal weird
+            del weird
+
+            # Collection will merge the object's reference count and make it zero.
+            gc.collect()
+
+            # Unfreeze the object, making it visible to the GC.
+            gc.unfreeze()
+            gc.collect()
+
+        thread = Thread(target=evil)
+        thread.start()
+        thread.join()
+
 
 if __name__ == "__main__":
     unittest.main()

Lib/test/test_gc.py

@@ -1249,18 +1249,6 @@ def test_tuple_untrack_counts(self):
         self.assertTrue(new_count - count > (n // 2))
 
 
-    @threading_helper.requires_working_threading()
-    def test_concurrent_freeze_unfreeze():
-        # GH-142975: On the free-threaded build, this would cause problems
-        # with objects that had a per-thread reference count.
-        def weird():
-            gc.freeze()
-            gc.collect()
-            gc.unfreeze()
-
-        threading_helper.run_concurrently(weird, 4)
-
-
 class IncrementalGCTests(unittest.TestCase):
     @unittest.skipIf(_testinternalcapi is None, "requires _testinternalcapi")
     @requires_gil_enabled("Free threading does not support incremental GC")