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SubjectRe: Change in functionality of futex() system call.
(2011/06/10 2:58), Peter Zijlstra wrote:
> On Thu, 2011-06-09 at 14:05 +0200, Peter Zijlstra wrote:
>> On Thu, 2011-06-09 at 20:37 +0900, KOSAKI Motohiro wrote:
>>> 1) check the pte of the target address is RW attribute.
>>> 2-1) if yes, it has no COW chance. we can safely use gup result.
>>> 2-2) if no, we have to fallback slow vma walk. maybe, it's okey.
>>> both RO mappings and COW are rare situation.
>>
>> Not so, clean file pages are RO, even if the vma is writable. We use the
>> fault to track dirty state with.
>
> Why can't something like
> http://marc.info/?l=linux-kernel&m=130737669810421 work once you restore
> the rw argument?

Yeah, I agree this is best way. Private RO mappings is not sane and no real
world users.




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