Re: [PATCH 26/31] sched, numa, mm: Add fault driven placement andmigration policy

[Peter Zijlstra]

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).
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