[Crash-utility] Re: Problem with using crash 4.0-2.21 on ppc

[Dave Anderson]

Rachita Kothiyal wrote:

>
> > Rachita Kothiyal wrote:
>
>
> >
> > This happens in get_idle_threads() when perusing the runqueues array,
> > where each per-cpu runqueue data structure contains a pointer to the
> > idle (swapper) task for that CPU.  Now, this process requires that the
> > per-cpu address manipulations are working correctly in order to find the
> > each cpu's runqueue data structure.  It looks like the ppc64 change
> > for per-cpu data accesses is suspect here:
> >
> > > Fix to recognize post-2.6.15 ppc64 kernels moving the per_cpu_offsets
> > > to the "paca" structure.  Without this patch, crash fails with the
> > > following error messages: "crash: cannot determine idle task addresses
> > > from init_tasks[] or runqueues[]" and "crash: cannot resolve
> > > init_task_union".  (pbadari at us.ibm.com)
> >
>
> Right, but I thought this patch fixed this problem.
> (I am using crash-4.0-2.21, and it includes this patch)

Right -- me too...   ;-)

>
>
> > >
> > > But I was able to run it ok on a live system.
> > >
> >
> > Same kernel?  I have no idea why there would be a difference
> > between live and vmcore.
>
> Yes, same kernel (2.6.16-rc4)
>

I'm sure Badari can give you more information, but you might start
by putting some debug printf's in his new ppc64_paca_init() function
to see whether it's calculating the same kt->__per_cpu_offset[cpu]
values on a live system vs. its associated vmcore?

Dave