Messages in this thread |  | | Date | Fri, 26 Oct 2012 16:14:30 +0200 | | From | Ingo Molnar <> | | Subject | Re: [PATCH 26/31] sched, numa, mm: Add fault driven placement and migration policy |
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* Peter Zijlstra <a.p.zijlstra@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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