* Peter Zijlstra <a.p.zijls...@chello.nl> wrote:
> On Fri, 2012-10-26 at 15:50 +0200, Ingo Molnar wrote:
> >
> > Oh, just found the reason:
> >
> > the ptep_modify_prot_start()/modify()/commit() sequence is
> > SMP-unsafe - it has to be done under the mmap_sem
> > write-locked.
> >
> > It is safe against *hardware* updates to the PTE, but not
> > safe against itself.
>
> Shouldn't the pte_lock serialize all that still? All sites
> that modify PTE contents should hold the pte_lock (and do
> afaict).
Hm, indeed.
Is there no code under down_read() (in the page fault path) that
modifies the pte via just pure atomics?
Thanks,
Ingo
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