Re: Threads continued ...

From: Rene Brun (Rene.Brun@cern.ch)
Date: Wed Aug 25 1999 - 17:20:25 MEST


Hello Hans,
Thanks for your efforts to communicate this very useful information.
Debugging threads is a non trivial task and this can only be done
in a real environment with a real application.
Obviously, we will implement all changes in the GUI classes that you
or other TThread users will communicate.

Rene Brun

Essel Dr.Hans-Georg wrote:
> 
> h.essel@gsi.de
> 
> Hi Valery,
> thanks for your very informative and helpful comments to the thread topic.
> Lets recall some facts.
> At the Fermilab meeting Rene stated in public that threads are supported
> in current root and that multithread canvas access works. He asked for
> people to test that and to report errors.
> So we did. The result was published in roottalk (July, 22) and in the Web
> where you can find a very detailed report. At that time we had only
> SMP machines available.
> The new information now is that some of the observed errors are due to
> bugs in Linux SMP which we could verify by simple X test programs.
> To summarize:
> 1. As we expected from the beginning and as you confirmed, root is not
> threadsave in general. One reason is object instantiation.
> 2. The concurrent canvas update from threads works on single CPU
> machines. On SMP machines it crashes with Linux kernel 2.0.
> Otto Schaile run our test program and found it crashing on SMP
> with kernel 2.2.10 and libc-2.0.7, but running with libc-2.1.1.
> Martin Purschke reported it running on kernel 2.2.2 and libc-2.07.
> 3. The root timer stops on SMP after some time, but runs on single
> CPU machines.
> Of cause we do not intend to run arbitrary root classes in threads.
> But to use root GUI online it would be very useful to handle the
> communication with the outside world in dedicated threads which in turn
> can update GUI widgets. We verified that this concept can work,
> when the SMP problem is solved.
> Cheers, Hans



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