Messages in this thread | | | Date | Wed, 6 Jul 2016 10:47:53 +0200 | From | Martin Schwidefsky <> | Subject | Re: [PATCH 2/2] s390/mm: use ipte range to invalidate multiple page table entries |
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On Wed, 06 Jul 2016 14:42:16 +0800 "Hillf Danton" <hillf.zj@alibaba-inc.com> 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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