On Wed, 06 Jul 2016 14:42:16 +0800
"Hillf Danton" <hillf.zj@xxxxxxxxxxxxxxx> wrote:
> > > >
> > > > +void ptep_invalidate_range(struct mm_struct *mm, unsigned long start,
> > > > + unsigned long end, pte_t *ptep)
> > > > +{
> > > > + unsigned long nr;
> > > > +
> > > > + if (!MACHINE_HAS_IPTE_RANGE || mm_has_pgste(mm))
> > > > + return;
> > > > + preempt_disable();
> > > > + nr = (end - start) >> PAGE_SHIFT;
> > > > + /* If the flush is likely to be local skip the ipte range */
> > > > + if (nr && !cpumask_equal(mm_cpumask(mm),
> > > > + cpumask_of(smp_processor_id())))
> > >
> > > s/smp/raw_smp/ to avoid adding schedule entry with page table
> > > lock held?
> >
> > There can not be a schedule entry with either the page table lock held
> > or the preempt_disable() a few lines above.
> >
> Yes, Sir.
>
> > > > + __ptep_ipte_range(start, nr - 1, ptep);
> > > > + preempt_enable();
>
> Then would you please, Sir, take a look at another case where
> preempt is enabled?
You are still a bit cryptic, are you trying to tell me that your hint is
about trying to avoid the preempt_enable() call?
The reason why I added the preempt_disable()/preempt_enable() pair to
ptep_invalidate_range is that I recently got bitten by a preempt problem
in the ptep_xchg_lazy() function which is used for ptep_get_and_clear().
Now ptep_get_and_clear() is used in vunmap_pte_range() which is called
while preemption is allowed.
To keep things symmetrical it seems sensible to explicitely disable
preemption on all ptep_xxx code paths with cpu mask checks, no?
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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