Re: [PATCH 0/4] futex: get_user_pages_fast() for shared futexes

Ingo Molnar
2008-09-30T10:39:38Z

* Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> On Sunday 28 September 2008 02:17, Ingo Molnar wrote:
> > * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > > Since get_user_pages_fast() made it in, I thought to give this another
> > > try. Lightly tested by disabling the private futexes and running some
> > > java proglets.
> >
> > hm, very interesting. Since this is an important futex usecase i started
> > testing it in tip/core/futexes:
> >
> > cd33272: futex: cleanup fshared
> > a135356: futex: use fast_gup()
> > 39ce77b: futex: reduce mmap_sem usage
> > 0d7a336: futex: rely on get_user_pages() for shared futexes
> >
> > Nick, it would be nice to get an Acked-by/Reviewed-by from you, before
> > we think about whether it should go upstream.
>
> Yeah, these all look pretty good. It's nice to get rid of mmap sem here.
>
> Which reminds me, we need to put a might_lock mmap_sem into
> get_user_pages_fast...
>
> But these patches look good to me (last time we discussed them I thought
> there was a race with page truncate, but it looks like you've closed that
> by holding page lock over the whole operation...)
>
> Nice work, Peter.

great - i've added your Acked-by to the patches and have activated the
tip/core/futexes branch for tip/auto-core-next linux-next integration.

here are the commits:

42569c3: futex: fixup get_futex_key() for private futexes
c2f9f20: futex: cleanup fshared
734b05b: futex: use fast_gup()
6127070: futex: reduce mmap_sem usage
38d47c1: futex: rely on get_user_pages() for shared futexes

Thanks,

Ingo