linux-kernel - Re: [PATCH -tip] Revert x86, mem: Optimize memcpy by avoiding memory false dependece

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Message-ID: <20100708150033.GA10224@Krystal>
Date:	Thu, 8 Jul 2010 11:00:33 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"Ma, Ling" <ling.ma@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH -tip] Revert x86, mem: Optimize memcpy by avoiding
	memory false dependece

* Ingo Molnar (mingo@...e.hu) wrote:
> 
> * Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
> 
> > * Ma, Ling (ling.ma@...el.com) wrote:
> > > Hi Mathieu
> > > 
> > > I did git revert as bellow
> > >     Revert "x86, mem: Optimize memcpy by avoiding memory false dependece"
> > > 
> > >     This reverts commit 77ff5e49c20bb72a99a12bfb00dbf90b2302f087.
> > > And I found the machine will crash with your config file
> > > 
> > > Could you revert the patch : 77ff5e49c20bb72a99a12bfb00dbf90b2302f087 on your
> > > machine, and check it again ?
> > 
> > Hi Ling,
> > 
> > I just successfully booted my machine 3 times in a row with a revert of 
> > commit a1e5278e40f16a4611264f8da9e557c16cb6f6ed from -tip. This is actually 
> > the same as reverting commit 77ff5e49c20bb72a99a12bfb00dbf90b2302f087, as 
> > a1e5278e40f16a4611264f8da9e557c16cb6f6ed is simply a merge of that commit 
> > (the diffs are exactly the same).
> > 
> > Without this revert, the machine gets to:
> 
> Please check latest -tip (2a74852 or later), the commit should be gone now.

Will do, thanks!

Mathieu

> 
> There's clearly some (boundary-condition?) bug in the assembly code of 
> 77ff5e49c2.
> 
> Thanks,
> 
> 	Ingo

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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