I think this is still an issue.

If I register signal.signal(signal.SIGINT, handler) in the main thread, I get a race between
- only the main thread receives the signal (everything is fine)
- both the main thread and currently running threads receive the signal => the handler is called multiple times => all kinds of resource-problems like "close failed in file object destructor: IOError: [Errno 9] Bad file descriptor" in thread cleanup functions

Note that I cannot even declare a sigintlock = threading.Lock() and use with sigintlock in the handler - if I print threading.current_thread() and sys.exit() directly afterwards in the locked area, I sometimes get two print outputs which show MainThread and Thread-1 being inside the locked area at the same time!

Is the synchronization broken or am I doing something wrong?

Is synchronization over handlers really the way to cope with this? Disabling signals for non-main threads currently seems more sensible to me.

Can someone please verify the race I get?