svn commit: r198868 - in head/sys: amd64/amd64 i386/i386

Kostik Belousov kostikbel at
Wed Nov 4 14:43:21 UTC 2009

On Wed, Nov 04, 2009 at 01:49:41PM +0100, Attilio Rao wrote:
> 2009/11/4 Ed Schouten <ed at>:
> > Hi Attilio,
> >
> > * Attilio Rao <attilio at> 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.
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