Re: [PATCH v6 5/8] slub: only IPI CPUs that have per cpu obj to flush

[Gilad Ben-Yossef <gilad@benyossef.com>]

On Wed, Jan 11, 2012 at 9:04 AM, Milton Miller <miltonm@bga.com> wrote:

>
> > mm/slub.c | 10 +++++++++-
> > 1 files changed, 9 insertions(+), 1 deletions(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 09ccee8..31833d6 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -2013,9 +2013,17 @@ static void flush_cpu_slab(void *d)
> > __flush_cpu_slab(s, smp_processor_id());
> > }
> >
> > +static int has_cpu_slab(int cpu, void *info)
> > +{
> > + struct kmem_cache *s = info;
> > + struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
> > +
> > + return !!(c->page);
>
> __flush_cpu_slab is careful to test that the the per_cpu_ptr is not
> NULL before referencing the page field.  free_percpu likewise ignores
> NULL pointers.  We need to check !!(c && c->page) here.
>
This is indeed what I did in the first iterations but Christoph indicated that
c could never be NULL in his review of the patch. See :
https://lkml.org/lkml/2011/11/15/207

I integrated all the other review comment of this patch though. Thanks!
Gilad

--
Gilad Ben-Yossef
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gilad@benyossef.com
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"Unfortunately, cache misses are an equal opportunity pain provider."
-- Mike Galbraith, LKML

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