Re: Fwd: -rt and PowerPC

[Chirag Jog <chirag@linux.vnet.ibm.com>]

Hi,
* Sven-Thorsten Dietrich <sven@thebigcorporation.com> [2007-12-28 08:23:32]:

> On Wed, 2007-12-26 at 09:53 +0530, Chirag Jog wrote:
> > * sven@thebigcorporation.com <sven@thebigcorporation.com> [2007-12-24 13:00:30]:
> > 
> > Hi,
> 
> Sorry for top-posting the last email. Have not learned how to inline on
> the Blackberry.
> 
> Comments below.
> 
> > > Do you have DEBUG and LOCKDEP configured?
> > CONFIG_PREEMPT_DEBUG is enabled
> > but LOCKDEP is not.
> > > 
> > > -----Original Message-----
> > > From:	Sripathi Kodi <sripathik@in.ibm.com>
> > > 
> > >     We are trying to get a ppc64 box booted with the -rt kernel.
> > > 
> > >     Tried the latest 2.6.24-rc5-rt1 kernel.
> > > 
> > >     Everything goes well [ kernel boots up etc] until the services
> > >     start coming up.
> > >     It takes a lot of time at Starting udev.
> > >     After which either services take too long to start or we get
> > >     SEGFAULT.
> 
> I have seen this exact behavior with lockdep enabled on earlier x86-SMP
> Kernels. I saw the issue predominantly on larger SMP machines, but it
> behaved much like a race. This was observed on 2.6.21 Kernels, I will
> try and verify whether .23 has the same behavior.
> 
> We eventually bisected it down to CONFIG_PROVE_LOCKING, but I wasn't
> totally convinced whethere the root cause was in lockdep, or
> elsewhere.  
> 
> > > 
> > >     This is easily reproducible. Also if we get a chance to login;
> > >     simple commands like ls, vi etc take either too long or get
> > >     SEGFAULT.
> 
> > > 
> > >     Booting the kernel with maxcpus=1 or turning off SMP, doesn't
> > >     solve the problem.
> > >
> 
> Hmmm, so have you COMPILED-out SMP, or just booted with nosmp?
> 
> It might help narrowing this down to compile a UP Kernel.
We have tried both options, compiled out SMP and boot with maxcpus=1.
Similar results.
Sripathi also tried with turning off HIGH_RES_TIMERS but didn't seem
to help.
The system took forever to come up.
> 
> Thanks
> 
> Sven
 
<snip>
-- 
Cheers,
Chirag Jog