Date: Wed, 4 Nov 2009 17:06:36 +0100 From: Attilio Rao <attilio@freebsd.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: svn-src-head@freebsd.org, Ed Schouten <ed@80386.nl>, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r198868 - in head/sys: amd64/amd64 i386/i386 Message-ID: <3bbf2fe10911040806r37f00a8dq2aa3ccd1e5c7b241@mail.gmail.com> In-Reply-To: <20091104144315.GH2331@deviant.kiev.zoral.com.ua> References: <200911040132.nA41WxtQ012750@svn.freebsd.org> <20091104055811.GY1293@hoeg.nl> <3bbf2fe10911040449j5938ca7eqca5829ceced66f48@mail.gmail.com> <20091104144315.GH2331@deviant.kiev.zoral.com.ua>
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2009/11/4, Kostik Belousov <kostikbel@gmail.com>: > On Wed, Nov 04, 2009 at 01:49:41PM +0100, Attilio Rao wrote: > > 2009/11/4 Ed Schouten <ed@80386.nl>: > > > Hi Attilio, > > > > > > * Attilio Rao <attilio@FreeBSD.org> wrote: > > >> Opteron rev E family of processor expose a bug where, in very rare > > >> ocassions, memory barriers semantic is not honoured by the hardware > > >> itself. As a result, some random breakage can happen in uninvestigable > > >> ways (for further explanation see at the content of the commit itself). > > > > > > Ooh. Sounds like an interesting bug. > > > > > > The bug doesn't manifest itself on UP, right? If so, maybe we should add > > > some very short instructions to the warning on how to disable SMP. > > > > Due to the semantic of the bug, I think that it can manifest itself on > > UP and a memory barrier failing on UP means that PREEMPTION can blow > > up. Considering this I wouldn't suggest anything different between the > > UP vs SMP case. > > CPU is always self-consistent, isn't it ? > > Also, I very much dislike idea of making our kernel a collection of > references to the man pages and URLs, esp. when URL point to the > resource not controlled by the project. Ok, as long as you are in favor of stripping the URL, I'm fine with it. Attilio -- Peace can only be achieved by understanding - A. Einstein
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