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SubjectRe: WARNING: __GFP_FS allocations with IRQs disabled (kmemcheck_alloc_shadow)
On Sun, Jul 08, 2012 at 04:01:44PM -0700, David Rientjes wrote:
> On Mon, 9 Jul 2012, JoonSoo Kim wrote:
>
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 8c691fa..5d41cad 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -1324,8 +1324,14 @@ static struct page *allocate_slab(struct
> > kmem_cache *s, gfp_t flags, int node)
> > && !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
> > int pages = 1 << oo_order(oo);
> >
> > + if (flags & __GFP_WAIT)
> > + local_irq_enable();
> > +
> > kmemcheck_alloc_shadow(page, oo_order(oo), flags, node);
> >
> > + if (flags & __GFP_WAIT)
> > + local_irq_disable();
> > +
> > /*
> > * Objects from caches that have a constructor don't get
> > * cleared when they're allocated, so we need to do it here.
>
> This patch is suboptimal when the branch is taken since you just disabled
> irqs and now are immediately reenabling them and then disabling them
> again. (And your patch is also whitespace damaged, has no changelog, and
> isn't signed off so it can't be applied.)

Agreed.

> The correct fix is what I proposed at
> http://marc.info/?l=linux-kernel&m=133754837703630 and was awaiting
> testing. If Rus, Steven, or Fengguang could test this then we could add
> it as a stable backport as well.

Acked-by: Fengguang Wu <fengguang.wu@intel.com>
Tested-by: Fengguang Wu <fengguang.wu@intel.com>

Thanks,
Fengguang


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