SMP ia32 support with Pistachio

[Stefan Kalkowski]

Hello Daniel,

On 01/14/2011 12:52 AM, Daniel Waddington - SISA wrote:
> Hi,
> 
>  
> 
> Has anyone managed to get Pistachio+Genode with SMP+ia32 running?  We
> have managed to get Pistachio+Genode+ia32 without SMP working fine.  

that's nice to hear!

> As soon as we compile SMP it goes into an endless loop.
> 
>  
> 
> Any ideas?

Well, I'm not sure what you exactly mean by 'it goes into an endless
loop'. Do you mean the kernel or Genode's core? Do you have some serial
output, or can you even enter the kernel-debugger?

In fact we normally only use the single-processor version of pistachio.
Nevertheless, we've tested SMP support today, and there seems to be a
general problem with SMP in the current version of pistachio. We got
different races sometimes even before 'core' (Genode's roottask) got
started.

In older versions of pistachio, SMP support seems to work, but there we
got minor problems with the old mapping-database. Possibly the SMP
version doesn't use the new mapping database implementation, at least in
the version we've tested (from 08.01.2010). Probably, Genode can easily
be reworked to use the old mapping semantic, but it has known stability
problems.

I think a better way is to solve the presumptive, current SMP support
problem in pistachio directly. You might ask the pistachio developers
for help[1]. Maybe you can reproduce the SMP problems with a tiny
example application?

Once, the pistachio port of Genode (formerly known as Bastei) was done
by Julian Stecklina[2] as study work, he successfully implemented
rudimentary SMP support into the cpu-session interface of Genode. So at
least at that point SMP worked with the predecessor of Genode together,
but that experimental code isn't part of Genode today.

Do you plan to extend Genode's cpu-session interface to support an
explicit cpu-migration of threads, or do you want to do load-balance
somehow implicitly?

> 
> Thanks
> Daniel Waddington
> 

You're welcome.

regards
Stefan Kalkowski

[1] http://l4ka.org/maillist.php
[2] http://os.inf.tu-dresden.de/papers_ps/jstecklina-beleg.pdf

-- 
Stefan Kalkowski
Genode Labs

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