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

[Attilio Rao]

2009/11/4, Dag-Erling Smørgrav <des at des.no>:
> Attilio Rao <attilio at FreeBSD.org> writes:
> > Log:
> >   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).
>
> According to the reference you gave, OpenSolaris has a workaround for
> this issue.  Perhaps we should adopt it?

IIRC, based on what I readed on-line, it could be still a WARNING msg,
but I didn't double-check for it.
On the other side, a possible complete solution would involve a
boot-time patching mechanism, but we don't have it right now
(differently from Linux) or disabling the SMP support, but it seems
mostly a too heavy loss of performance due to the rarely appearence of
the bug itself.

I think the WARNING msg is a good compromise to all these other approaches.

Attilio


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