gh-116604: Fix test_gc on free-threaded build

Lib/test/support/__init__.py

@@ -797,6 +797,16 @@ def disable_gc():
         if have_gc:
             gc.enable()
 
+@contextlib.contextmanager
+def gc_threshold(*args):
+    import gc
+    old_threshold = gc.get_threshold()
+    gc.set_threshold(*args)
+    try:
+        yield
+    finally:
+        gc.set_threshold(*old_threshold)
+
 
 def python_is_optimized():
     """Find if Python was built with optimizations."""

Lib/test/test_gc.py

@@ -5,7 +5,7 @@
 from test.support.import_helper import import_module
 from test.support.os_helper import temp_dir, TESTFN, unlink
 from test.support.script_helper import assert_python_ok, make_script
-from test.support import threading_helper
+from test.support import threading_helper, gc_threshold
 
 import gc
 import sys
@@ -1330,6 +1330,7 @@ def callback(ignored):
             # with an empty __dict__.
             self.assertEqual(x, None)
 
+    @gc_threshold(1000, 0, 0)
     def test_bug1055820d(self):
         # Corresponds to temp2d.py in the bug report.  This is very much like
         # test_bug1055820c, but uses a __del__ method instead of a weakref
@@ -1397,6 +1398,7 @@ def __del__(self):
             # empty __dict__.
             self.assertEqual(x, None)
 
+    @gc_threshold(1000, 0, 0)
     def test_indirect_calls_with_gc_disabled(self):
         junk = []
         i = 0