Re: [PATCH 2/2] Futex non-page-pinning fix

[Muli Ben-Yehuda]

On Tue, Aug 26, 2003 at 01:25:29AM -0700, Andrew Morton wrote:
> Muli Ben-Yehuda <mulix@xxxxxxxxx> wrote:

> >  How about combining something that's shared to all of the threads that
> >  share a futex but not system wide (the mm?) with something simple that
> >  won't change, like the page offset?
> 
> The mm's could well be independent.

I assumed all threads sharing a futex share an mm since you suggested
hashing on mm + vaddr?  

> Some userspace help would be needed to avoid defeating the hash.  In the
> case where a bunch of threads with a shared mm are waiting on the same
> futex things should automatically be OK.

Userspace help would be fine, but relying only on userspace could lead
to an immediate DoS by forcing the hash to always hash to the same
bucket.
-- 
Muli Ben-Yehuda
http://www.mulix.org

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