Date: Wed, 4 Nov 2009 16:43:15 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Attilio Rao <attilio@freebsd.org> 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: <20091104144315.GH2331@deviant.kiev.zoral.com.ua> In-Reply-To: <3bbf2fe10911040449j5938ca7eqca5829ceced66f48@mail.gmail.com> References: <200911040132.nA41WxtQ012750@svn.freebsd.org> <20091104055811.GY1293@hoeg.nl> <3bbf2fe10911040449j5938ca7eqca5829ceced66f48@mail.gmail.com>
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--54u2kuW9sGWg/X+X Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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. >=20 > 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. --54u2kuW9sGWg/X+X Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAkrxkwIACgkQC3+MBN1Mb4isvACg5S8wnOv93nIr3CtXoN86fXrO Em8AoLB0JX5z0jghg5cttbDKDdd+CfE9 =TN3q -----END PGP SIGNATURE----- --54u2kuW9sGWg/X+X--
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