SF bug 1061968: threads: segfault or Py_FatalError at exit PyGILState_Ensure(): The fix in 2.4a3 for bug 1010677 reintroduced thread shutdown race bug 225673. Repaired by (once again) ensuring the GIL is held whenever deleting a thread state. Alas, there's no useful test case for this shy bug. Four years ago, only Guido could provoke it, on his box, and today only Armin can provoke it on his box. I've never been able to provoke it (but not for lack of trying!). This is a critical fix for 2.3.5 too, since the fix for 1010677 got backported there already and so also reintroduced 225673. I don't intend to backport this fix. For whoever (if anyone) does, there are other thread fixes in 2.4 that need backporting too, and I bet they need to happen first for this patch to apply cleanly.