Re: [PATCH 08/10] ia64: Convert cpu_sibling_map to a per_cpu data array (v3)

Mike Travis
2007-10-03T19:33:20Z

Hi Paul,

I just now found this. I'll take a look immediately. I tried it
on a couple of systems but not margin.

Thanks,
Mike

Paul Jackson wrote:
> Mike,
>
> I think there is a bug either in this ia64 patch, or in the related
> generic arch patch: Convert cpu_sibling_map to be a per cpu variable
> (v3).
>
> It dies early in boot on me, on the SGI internal 8 processor IA64
> system that you and I know as 'margin'. The death is a hard hang, due
> to a corrupt stack, due to a bogus cpu index.
>
> I haven't tracked it down all the way, but have gotten this far. If I add
> the following patch, I get a panic on the BUG_ON if I have these two patches
> in 2.6.23-rc8-mm1, but it boots just fine if I don't have these two patches.
>
> It seems that the "cpu_sibling_map[cpu]" cpumask_t is empty (all zero
> bits) with your two patches applied, but has some non-zero bits
> otherwise, which leads to 'group' being NR_CPUS instead of a useful CPU
> number. Unfortunately, I have no idea why the "cpu_sibling_map[cpu]"
> cpumask_t is empty -- good luck on that part.
>
> The patch that catches this bug earlier is this:
>
> --- 2.6.23-rc8-mm1.orig/kernel/sched.c 2007-09-28 01:42:20.144561024 -0700
> +++ 2.6.23-rc8-mm1/kernel/sched.c 2007-09-28 02:27:14.239075497 -0700
> @@ -5905,6 +5905,7 @@ static int cpu_to_phys_group(int cpu, co
> #else
> group = cpu;
> #endif
> + BUG_ON(group == NR_CPUS);
> if (sg)
> *sg = &per_cpu(sched_group_phys, group);
> return group;
>
>