Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction abstraction

[Jeremy Fitzhardinge]

Benjamin Herrenschmidt wrote:
> On Mon, 2008-06-16 at 04:30 -0700, Jeremy Fitzhardinge wrote:
>   
> > The only current user of this interface is mprotect
> >     
>
> Do you plan to use it with fork ultimately ?
>   

Good point, I'd overlooked that.  I guess that means using it in 
ptep_set_wrprotect().

At present the x86 ptep_set_wrprotect() just uses clear_bit on the pte, 
which is a locked cycle.  Is that significantly cheaper than an xchg + 
set?  (Same number of locked operations...)

   J
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