Re: Realtime Preemption, 2.6.12, Beginners Guide?

[Alistair John Strachan <s0348365@sms.ed.ac.uk>]

On Saturday 09 Jul 2005 17:04, Alistair John Strachan wrote:
> On Saturday 09 Jul 2005 16:57, Ingo Molnar wrote:
> > * Alistair John Strachan <s0348365@sms.ed.ac.uk> wrote:
> > > Okay, I'll send you the vmlinux from -18 with a new digital photo, and
> > > config, with CONFIG_4KSTACKS enabled.
> >
> > this crash too seems to indicate trigger_softirqs()/wakeup_softirqd().
> > Somewhere we somehow corrupt the stack and e.g. in oops7.jpg we return
> > to 00c011ed. Note that it's a right-shifted address that could be one of
> > these:
> >
> >  c011ed50 t wakeup_softirqd
> >  c011ed80 t trigger_softirqs
> >
> > but it looks pretty weird. DEBUG_STACK_POISON (and the full-debug
> > .config i sent) could perhaps uncover other types of stack corruptions.
>
> You weren't kidding about the overhead from DEBUG_STACK_POISON.
> Unfortunately that config causes a triple fault randomly after boot. The
> machine doesn't crash, or oops, it just resets.
>
> This problem has gone from bad to worse :-)

Okay, maybe not. Some combination of the debug options you enabled causes this 
problem, but DEBUG_STACK_POISON itself is not the cause. Today I compiled Yet 
Another (tm) CONFIG_4KSTACKS kernel with DEBUG_STACK_POISON, 
CONFIG_DEBUG_STACKOVERFLOW and CONFIG_LATENCY_TRACE, which worked fine (from 
a random reboot perspective).

I've also upgraded GCC to 4.0.1 as Jakub highlighted elsewhere in this thread 
that it had been released.

Here's a screenshot of the oops. Notice that "stack left" is now -52. We've 
confirmed this is a stack overflow!

http://devzero.co.uk/~alistair/oops8.jpeg

I'm going to try the 8K stack kernel with the same stuff and see if I can get 
a stack trace. I hope this is the beginning of the end for this problem.

-- 
Cheers,
Alistair.

personal:   alistair()devzero!co!uk
university: s0348365()sms!ed!ac!uk
student:    CS/CSim Undergraduate
contact:    1F2 55 South Clerk Street,
            Edinburgh. EH8 9PP.
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