Re: [Webware-discuss] problem with ctrl-C handling in ThreadedAppServer

[Geoff T. <gta...@na...>]

It looks to me that on Linux, Ctrl-C can trigger an exception in ANY thread,
not just the main thread.  I think this might make it impossible to handle
Ctrl-C safely in ThreadedAppServer on Linux.

I've already developed a fix for Windows NT, but it might do no good on
Linux.  Should I check it in anyway?

Tom Schwaller wrote:

> Geoff Talvola wrote:
> >
> > I've identified a problem with Ctrl-C handling in ThreadedAppServer such
> > that it can sometimes fail to shut down and needs to be killed.  The
> > reason is that Ctrl-C causes the main Python thread to immediately throw
> > an exception, wherever it may be in the code.  If you happen to press
> > Ctrl-C while the main thread is blocking, waiting to put something into
> > the request queue, then the queue gets into a state where it blocks
> > indefinitely the next time you try to put something into the queue.
> >
> > Here's a test program that illustrates the problem.  I've tried it on NT
> > with Python 1.5.2.  If I run it with argument 0, it never exits when I
> > press Ctrl-C and has to be killed.  But if I run it with argument 1, it
> > works fine because it puts the Queue manipulation into a separate thread
> > -- this would be a way to fix ThreadedAppServer.
> >
> > If someone could run it on Linux and let me know if you get the same
> > results, I'd appreciate it.
>
> Under Linux I have to kill them in BOTH cases. Your
> prediction does not seem to work..
>
> Exception in thread Thread-3:
> Traceback (innermost last):
>   File "/usr/lib/python1.5/threading.py", line 376, in __bootstrap
>     self.run()
>   File "/usr/lib/python1.5/threading.py", line 364, in run
>     apply(self.__target, self.__args, self.__kwargs)
>   File "testthreads.py", line 8, in threadfunc
>     time.sleep(1.0)
> IOError: [Errno 4] Unterbrechung während des Betriebssystemaufrufs
>
> Exception in thread Thread-4:
> Traceback (innermost last):
>   File "/usr/lib/python1.5/threading.py", line 376, in __bootstrap
>     self.run()
>   File "/usr/lib/python1.5/threading.py", line 364, in run
>     apply(self.__target, self.__args, self.__kwargs)
>   File "testthreads.py", line 8, in threadfunc
>     time.sleep(1.0)
> IOError: [Errno 4] Unterbrechung während des Betriebssystemaufrufs
>
> Ignore the German Error messages. ... Means "interrupt during system
> call" ...
>
> --
>
> Tom Schwaller
> http://www.linux-community.de
> http://www.linux-magazin.de/

--


- Geoff Talvola
  Parlance Corporation
  gtalvola@NameConnector.com