> This sometimes leads to a deadlock when the process is crashing, handled via faulthandler, instead of a crash with stacktrace information printed.  The opposite of the happy debugging experience it is intended to provide.

Is it an hypothetical analysis by reading the C code, or did you get deadlock in practice? If yes, can you please explain how to reproduce the bug and try to get the gdb traceback of the thread which is blocked in faulthandler?

In general, faulthandler is an opt-in option for developers, it's not perfect, it only promises best-effort ;-) But I'm a little bit surprised of your deadlock issue. test_faulthandler is running on a wide range of platforms and I didn't notice such deadlock on buildbots yet.