[3.13] gh-119585: Fix crash involving `PyGILState_Release()` and `PyThreadState_Clear()` (GH-119753) (#119859)

Make sure that `gilstate_counter` is not zero in when calling
`PyThreadState_Clear()`. A destructor called from `PyThreadState_Clear()` may
call back into `PyGILState_Ensure()` and `PyGILState_Release()`. If
`gilstate_counter` is zero, it will try to create a new thread state before
the current active thread state is destroyed, leading to an assertion failure
or crash.
(cherry picked from commit bcc1be39cb1d04ad9fc0bd1b9193d3972835a57c)

Co-authored-by: Sam Gross <colesbury@gmail.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/Lib/test/test_capi/test_misc.py b/Lib/test/test_capi/test_misc.py
index ed42d7b..f3d16e4 100644
--- a/Lib/test/test_capi/test_misc.py
+++ b/Lib/test/test_capi/test_misc.py
@@ -2890,6 +2890,22 @@ class TestThreadState(unittest.TestCase):
 
     @threading_helper.reap_threads
     @threading_helper.requires_working_threading()
+    def test_thread_gilstate_in_clear(self):
+        # See https://github.com/python/cpython/issues/119585
+        class C:
+            def __del__(self):
+                _testcapi.gilstate_ensure_release()
+
+        # Thread-local variables are destroyed in `PyThreadState_Clear()`.
+        local_var = threading.local()
+
+        def callback():
+            local_var.x = C()
+
+        _testcapi._test_thread_state(callback)
+
+    @threading_helper.reap_threads
+    @threading_helper.requires_working_threading()
     def test_gilstate_ensure_no_deadlock(self):
         # See https://github.com/python/cpython/issues/96071
         code = textwrap.dedent("""