bpo-20526: Fix PyThreadState_Clear(): don't decref frame (GH-19120) (GH-19136)
PyThreadState.frame is a borrowed reference, not a strong reference:
PyThreadState_Clear() must not call Py_CLEAR(tstate->frame).
Remove test_threading.test_warnings_at_exit(): we cannot warranty
that the Python thread state of daemon threads is cleared in a
reliable way during Python shutdown.
(cherry picked from commit 5804f878e779712e803be927ca8a6df389d82cdf)
diff --git a/Python/pystate.c b/Python/pystate.c
index 9f99060..3e10855 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -762,11 +762,19 @@
{
int verbose = tstate->interp->config.verbose;
- if (verbose && tstate->frame != NULL)
+ if (verbose && tstate->frame != NULL) {
+ /* bpo-20526: After the main thread calls
+ _PyRuntimeState_SetFinalizing() in Py_FinalizeEx(), threads must
+ exit when trying to take the GIL. If a thread exit in the middle of
+ _PyEval_EvalFrameDefault(), tstate->frame is not reset to its
+ previous value. It is more likely with daemon threads, but it can
+ happen with regular threads if threading._shutdown() fails
+ (ex: interrupted by CTRL+C). */
fprintf(stderr,
"PyThreadState_Clear: warning: thread still has a frame\n");
+ }
- Py_CLEAR(tstate->frame);
+ /* Don't clear tstate->frame: it is a borrowed reference */
Py_CLEAR(tstate->dict);
Py_CLEAR(tstate->async_exc);