From: Mel Gorman <mgorman@suse.de>
To: zhang.yi20@zte.com.cn
Cc: "'Dave Hansen'" <dave.hansen@linux.intel.com>,
"'Darren Hart'" <dvhart@linux.intel.com>,
linux-kernel@vger.kernel.org, "'Ingo Molnar'" <mingo@kernel.org>,
"'Peter Zijlstra'" <peterz@infradead.org>,
"'Thomas Gleixner'" <tglx@linutronix.de>,
wetpzy@163.com, Zhang Yi <wetpzy@gmail.com>
Subject: Re: Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage
Date: Fri, 10 May 2013 10:42:22 +0100 [thread overview]
Message-ID: <20130510094222.GL11497@suse.de> (raw)
In-Reply-To: <OF48CE8C5D.403E463A-ON48257B67.0031867F-48257B67.00324443@zte.com.cn>
On Fri, May 10, 2013 at 05:08:30PM +0800, zhang.yi20@zte.com.cn wrote:
>
>
> Mel Gorman <mgorman@suse.de> wrote on 2013/05/07 23:20:07:
>
> >
> > Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage
> >
> > On Tue, May 07, 2013 at 08:23:48PM +0800, Zhang Yi wrote:
> > > diff -uprN linux3.9-orig/kernel/futex.c linux3.9/kernel/futex.c
> > > --- linux3.9-orig/kernel/futex.c 2013-04-15 00:45:16.000000000 +0000
> > > +++ linux3.9/kernel/futex.c 2013-05-06 16:24:40.403525000 +0000
> > > @@ -215,6 +215,22 @@ static void drop_futex_key_refs(union fu
> > > }
> > > }
> > >
> > > +/*
> > > +* Get subpage index in compound page, and add it into futex_key.
> > > +*/
> > > +static void key_add_compound_idx(union futex_key *key,
> > > + struct page *head_page, struct page *page)
> > > +{
> > > + int compound_idx;
> > > +
> > > + if (compound_order(head_page) >= MAX_ORDER)
> > > + compound_idx = page_to_pfn(page) - page_to_pfn(head_page);
> > > + else
> > > + compound_idx = page - head_page;
> > > +
> > > + key->both.offset |= compound_idx << PAGE_SHIFT;
> > > +}
> > > +
> >
> > This implicitely assumies it is dealing with a hugetlbfs page. Today, it
> > is the case that an inode-based futex with PageCompound is a hugetlbfs
> > page but that could change in the future if THP ever backs files. This
> > would then break again except it would be harder to fix because THP pages
> > can be collapsed underneath you after the futex key has been generated.
> >
> > As this problem is hugetlbfs-specific should the fix be firmly in
> hugetlbfs
>
> I think we should do.
> Eg, user applications want high performance, they may use DPDK which using
> hugetlbfs.
>
>
> Should I rework the patch like the following code, and test it?
>
Yes please, making sure to fix the bug Thomas pointed out.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2013-05-10 9:42 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-26 12:13 [PATCH] futex: bugfix for futex-key conflict when futex use hugepage Zhang Yi
2013-04-26 18:26 ` Thomas Gleixner
2013-05-07 12:23 ` Zhang Yi
2013-05-07 15:20 ` Mel Gorman
2013-05-07 15:24 ` Thomas Gleixner
2013-05-07 15:54 ` Mel Gorman
2013-05-10 9:08 ` zhang.yi20
2013-05-10 9:42 ` Mel Gorman [this message]
2013-05-07 12:34 ` Zhang Yi
-- strict thread matches above, loose matches on Subject: below --
2013-05-15 13:57 Zhang Yi
2013-05-15 14:20 ` Mel Gorman
2013-05-16 1:16 ` zhang.yi20
2013-05-16 1:30 ` Darren Hart
2013-05-16 2:00 ` zhang.yi20
2013-06-24 21:02 ` Darren Hart
2013-06-25 13:19 ` Zhang Yi
2013-06-25 18:23 ` Darren Hart
2013-06-25 19:41 ` Thomas Gleixner
2013-04-16 18:37 Dave Hansen
2013-04-17 7:47 ` zhang.yi20
2013-04-16 17:57 Darren Hart
2013-04-17 9:55 ` zhang.yi20
2013-04-17 14:18 ` Darren Hart
2013-04-17 15:26 ` Dave Hansen
2013-04-17 15:51 ` Darren Hart
2013-04-18 8:05 ` zhang.yi20
2013-04-18 14:34 ` Darren Hart
2013-04-19 2:13 ` zhang.yi20
2013-04-19 2:45 ` Darren Hart
2013-04-19 7:03 ` zhang.yi20
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