Messages in this thread | | | Date | Mon, 21 Sep 2009 09:46:44 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 1/3] slqb: Do not use DEFINE_PER_CPU for per-node data |
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On Mon, Sep 21, 2009 at 09:24:00AM +0300, Pekka Enberg wrote: > Hi Tejun, > > On Mon, 2009-09-21 at 00:55 +0900, Tejun Heo wrote: > > Pekka Enberg wrote: > > > Tejun Heo wrote: > > >> Pekka Enberg wrote: > > >>> On Fri, Sep 18, 2009 at 10:34 PM, Mel Gorman <mel@csn.ul.ie> wrote: > > >>>> SLQB used a seemingly nice hack to allocate per-node data for the > > >>>> statically > > >>>> initialised caches. Unfortunately, due to some unknown per-cpu > > >>>> optimisation, these regions are being reused by something else as the > > >>>> per-node data is getting randomly scrambled. This patch fixes the > > >>>> problem but it's not fully understood *why* it fixes the problem at the > > >>>> moment. > > >>> Ouch, that sounds bad. I guess it's architecture specific bug as x86 > > >>> works ok? Lets CC Tejun. > > >> > > >> Is the corruption being seen on ppc or s390? > > > > > > On ppc. > > > > Can you please post full dmesg showing the corruption? Also, if you > > apply the attached patch, does the added BUG_ON() trigger? > > I don't have the affected machines, Sachin and Mel do. >
More accurately, Sachin does but he gave me access to the machine for this bug so I can use it when it's otherwise idle.
> Pekka > > > diff --git a/include/linux/percpu.h b/include/linux/percpu.h > > index 878836c..fb690d2 100644 > > --- a/include/linux/percpu.h > > +++ b/include/linux/percpu.h > > @@ -127,7 +127,7 @@ extern int __init pcpu_page_first_chunk(size_t reserved_size, > > * dynamically allocated. Non-atomic access to the current CPU's > > * version should probably be combined with get_cpu()/put_cpu(). > > */ > > -#define per_cpu_ptr(ptr, cpu) SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))) > > +#define per_cpu_ptr(ptr, cpu) ({ BUG_ON(!(ptr)); SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))); }) > > > > extern void *__alloc_reserved_percpu(size_t size, size_t align); >
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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