Re: [PATCH 2.6.21-rc3-mm2 3/4] futex_requeue_pi optimization

[Pierre Peiffer]

Peter Zijlstra a Ãcrit :

> Unfortunately not, nonlinear vmas don't have a linear relation between
> address and offset. What you would need to do is do a linear walk of the
> page tables. But even that might not suffice if nonlinear vmas may form
> a non-injective, surjective mapping.
>
> /me checks..
>
> Hmm, yes that seems valid, so in general, this reverse mapping does not
> uniquely exist for non-linear vmas. :-(
>
> What to do... disallow futexes in nonlinear mappings, 

> store the address in the key?   <<

That seems to be the only solution... :-/

> the vma_prio_tree would be able to give all vmas associated with a
> mapping.

Thanks for your help.

--
Pierre
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