linux-kernel - Re: Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage

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Date:	Thu, 16 May 2013 09:16:20 +0800
From:	zhang.yi20@....com.cn
To:	Mel Gorman <mgorman@...e.de>
Cc:	"'Darren Hart'" <dvhart@...ux.intel.com>,
	linux-kernel@...r.kernel.org, "'Ingo Molnar'" <mingo@...nel.org>,
	"'Peter Zijlstra'" <peterz@...radead.org>,
	"'Thomas Gleixner'" <tglx@...utronix.de>,
	Zhang Yi <wetpzy@...il.com>
Subject: Re: Re: [PATCH] futex: bugfix for futex-key conflict when futex use
 hugepage



Mel Gorman <mgorman@...e.de> wrote on 2013/05/15 22:20:35:


> Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage
>
> On Wed, May 15, 2013 at 09:57:03PM +0800, Zhang Yi wrote:
> > The futex-keys of processes share futex determined by page-offset,
> > mapping-host, and mapping-index of the user space address. User
> > appications using hugepage for futex may lead to futex-key conflict.
> >
> > Assume there are two or more futexes in diffrent normal pages of the
> > hugepage, and each futex has the same offset in its normal page,
> > causing all the futexes have the same futex-key.
> >
> > This patch adds the normal page index in the compound page into
> > the pgoff of futex-key.
> >
> > Steps to reproduce the bug:
> > 1. The 1st thread map a file of hugetlbfs, and use the return address
> > as the 1st mutex's address, and use the return address with PAGE_SIZE
> > added as the 2nd mutex's address.
> > 2. The 1st thread initialize the two mutexes with pshared attribute,
> > and lock the two mutexes.
> > 3. The 1st thread create the 2nd thread, and the 2nd thread block on
> > the 1st mutex.
> > 4. The 1st thread create the 3rd thread, and the 3rd thread block on
> > the 2nd mutex.
> > 5. The 1st thread unlock the 2nd mutex, the 3rd thread cannot take
> > the 2nd mutex, and may block forever.
> >
> >
> > Signed-off-by: Zhang Yi <zhang.yi20@....com.cn>
> > Tested-by: Ma Chenggong <ma.chenggong@....com.cn>
> > Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> > Reviewed-by: Darren Hart <dvhart@...ux.intel.com>
> > Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>
> > Reviewed-by: Mel Gorman <mgorman@...e.de>
> > Reviewed-by: Liu Dong <liu.dong3@....com.cn>
> > Reviewed-by: Cui Yunfeng <cui.yunfeng@....com.cn>
> > Reviewed-by: Lu Zhongjun <lu.zhongjun@....com.cn>
> > Reviewed-by: Jiang Biao <jiang.biao2@....com.cn>
> >
>
> Did all these people really review it? I just whinged about the last
patch
> and didn't put a Reviewed-by on it. That said, I don't actually have a
> problem with this patch and I assumed it passed your testing so
>
I mistakenly think that I should list all the people here. : )
Shall I cleanup the name list and send the patch again?

> Reviewed-by: Mel Gorman <mgorman@...e.de>
>
> The others might not agree though.
>
> I note the conversion from int offset to long offset in futex_key appears
> to have gotten lost. Is that in a separate cleanup patch now?

In old patch, I add the compound index into offset, so I make the offset
from int
to long. It is unnecessary for this patch.

>
> --
> Mel Gorman
> SUSE Labs


BTW, Does anyone have other advices for the patch?

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