[Python-Dev] threading bug?

[Thomas Heller]

From: "Guido van Rossum" <guido@python.org>
> > [Apologies, I also asked this on c.l.p, but got no
> > answer so far. I have not too much time left before
> > I will be away for nearly 2 weeks]
> > 
> > I wonder if this is a bug. I'm running a deamon thread doing
> > some work in the background, and sometimes when Python exits
> > I get tracebacks like this:
> > 
> > Unhandled exception in thread:
> > Traceback (most recent call last):
> >   File "c:\python21\lib\threading.py", line 393, in __bootstrap
> >     self.__stop()
> >   File "c:\python21\lib\threading.py", line 399, in __stop
> >     self.__block.notifyAll()
> >   File "c:\python21\lib\threading.py", line 235, in notifyAll
> >     self.notify(len(self.__waiters))
> >   File "c:\python21\lib\threading.py", line 217, in notify
> >     me = currentThread()
> > TypeError: object of type 'None' is not callable
> > 
> > This traceback does not appear when I register an atexit
> > function to stop the thread.
> > 
> > Is this a bug? Aren't daemon threads supposed to clean up
> > themselves?
> 
> This is probably a result of the destructive module finalization.
> When Py_Finalize() is called, threads that are still running are not
> killed.  But Py_Finalize() replaces the values of all globals in
> modules with None (it could just clear the module's dictionary but
> there was some reason for doing it this way) and that is what you are
> probably seeing.
> 
> If there was a primitive to kill a thread, we might use it in
> Py_Finalize() -- but there isn't (it's been requested but it's hard to
> see how to do it safely).

But it seems the system is trying to stop the thread(s),
maybe too late. In my case, atexit.register(self.stop)
makes a clean shutdown.
My point is: should the threading module do this?
I can easily live with doing it myself - I just don't know
if this is intended or required.

Thomas