Handling a signal in a thread that has exited and has not been
detached or joined with leads to an assert failing it glibc:

hurdsig.c:804: _hurd_internal_post_signal: Unexpected error: (ipc/send) invalid destination port.

After this, the program hangs and doesn't respond to any signals
other than SIGKILL.  My guess is that signal handling has been
disabled and it hangs while waiting for the abort signal to be
handled.

Also ps stops working after this and hangs without outputting
anything.  So the proc server might also be affected.

A test has been attached.  Be sure to background it because ^C etc.
doesn't work, leaving your terminal useless.