At the first CTRL+c, the main thread exit and enters Py_Finalize() which calls wait_for_thread_shutdown() (in Python: threading._shutdown()).

The problem is that the second call interrupted threading._shutdown() (still in the main thread).

> #9  0x000000000043d1d5 in PyGC_Collect () at Modules/gcmodule.c:1604
> #10 0x000000000041e959 in Py_Finalize () at Python/pythonrun.c:605

At this point, we can expect that only one Python thread is running because wait_for_thread_shutdown() has been called, but there are between 2 and 9 running Python threads.

If wait_for_thread_shutdown() is interrupted, maybe Python should kill all other threads with pthread_kill() or something like that.

Or wait_for_thread_shutdown() should maybe block SIGINT and SIGTERM signals using pthread_sigmark()?