Re: a really really weird crash on swarm

[Ralf Baechle <ralf@linux-mips.org>]

On Mon, Aug 19, 2002 at 02:57:14PM +0200, Maciej W. Rozycki wrote:

> > Really odd because the register only lost the upper 16 bits; the lower 16
> > bits still have their expected value.
> 
>  It is a typical symptom of a register being corrupted between a "lui" and
> an "addiu"  -- an exception must have done it in the immediately preceding
> code.  You might be able to track a reason down by carefully studying
> possible exception paths at the place of the problem.  Unfortunately you
> don't have much of the state preserved at this stage -- you only know
> which register was corrupted. 

Little exception potencial in this case as the interrupts got disabled and
the addresses used were rsp. should all be in KSEG0.

>  Another possible approach is to add some code that compares the values of
> the register upon an exception entry and exit and wait for it to trigger
> -- for a single register it shouldn't be too tough and you have still much
> of the state available before an "rfe" or "eret".

Don't try to think too deterministic - Jun was working on first silicon, so
not necessarily on a deterministic platform as we'd like.  Fortunately
as you may have seen in the kernel code there's already newer silicon so
I'd simply file this one to /dev/null for now.

  Ralf