Add a test.

Author: ZeroIntensity

Lib/test/test_gc.py

@@ -1249,6 +1249,18 @@ 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")