On Fri, 2009-05-22 at 19:27 +1000, Benjamin Herrenschmidt wrote:
> On Wed, 2009-05-20 at 19:12 +0900, Saito Hideo wrote:
>
> > I think that the tlb should be cleared before mm->context.id is set
> > MMU_NO_CONTEXT.
>
> You are right, this definitely looks like a bug on platforms that have
> HW support for the tlbil instruction (and thus care about the PID for
> flushing) which afaik is only the case of recent freescale chips.
In fact, you are doubly right in that it also happens on other platforms
because local_flush_tlb_mm() will check if the PID is MMU_NO_CONTEXT
regardless of what tlbilx supports.. oops
Looks like I only ran my context torture test with CONFIG_SMP enabled.
Shame on me.
> Have you verified that this change fixes your problem ?
>
> Can you re-submit to linuxppc-dev@ozlabs.org mailing list, along with
> proper changeset comment and signed-off-by: line ?
>
> Cheers,
> Ben.
>
> > --- arch/powerpc/mm/mmu_context_nohash.c.orig 2009-03-24
> > 08:12:14.000000000 +0900
> > +++ arch/powerpc/mm/mmu_context_nohash.c 2009-05-20 18:33:53.000000000
> > +0900
> > @@ -122,22 +122,22 @@ static unsigned int steal_context_up(uns
> > struct mm_struct *mm;
> > int cpu = smp_processor_id();
> >
> > /* Pick up the victim mm */
> > mm = context_mm[id];
> >
> > pr_debug("[%d] steal context %d from mm @%p\n", cpu, id, mm);
> >
> > - /* Mark this mm has having no context anymore */
> > - mm->context.id = MMU_NO_CONTEXT;
> > -
> > /* Flush the TLB for that context */
> > local_flush_tlb_mm(mm);
> >
> > + /* Mark this mm has having no context anymore */
> > + mm->context.id = MMU_NO_CONTEXT;
> > +
> > /* XXX This clear should ultimately be part of local_flush_tlb_mm */
> > __clear_bit(id, stale_map[cpu]);
> >
> > return id;
> > }
> >
> > #ifdef DEBUG_MAP_CONSISTENCY
> > static void context_check_map(void)
> > --
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