From: Ralf Baechle <ralf@oss.sgi.com>
To: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Cc: Jason Gunthorpe <jgg@debian.org>,
linux-mips@fnet.fr, linux-mips@oss.sgi.com
Subject: Re: [patch] linux 2.4.17: An mb() rework
Date: Mon, 4 Feb 2002 18:02:58 +0100 [thread overview]
Message-ID: <20020204180258.A6124@dea.linux-mips.net> (raw)
In-Reply-To: <Pine.GSO.3.96.1020131115837.5578A-100000@delta.ds2.pg.gda.pl>; from macro@ds2.pg.gda.pl on Thu, Jan 31, 2002 at 01:17:39PM +0100
On Thu, Jan 31, 2002 at 01:17:39PM +0100, Maciej W. Rozycki wrote:
> Certain DECstation models have a write-back buffer that needs to be
> handled explicitly. For example rmb() is "1: bc0f 1b" for the R3220 WB
> chip. Wmb() is null, certainly, as the buffer is strongly-ordered. See
> arch/mips/dec/wbflush.c for details.
Just as an aside that isn't directly relevant to DECstations. To date
all MIPS _processors_ are strongly ordered. I now know of at least one
processor that implements a weakly ordered memory model, so the assumption
of a strongly ordered memory model has become void for large parts of the
kernel. Even before that some systems had strongly ordered processors in
system environments that may reorder requests.
Bugs due to surprise memory reordering are entirely unfun to debug, so be
paranoid. They're out there to get you ...
Ralf
next prev parent reply other threads:[~2002-02-04 19:19 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-30 14:56 [patch] linux 2.4.17: An mb() rework Maciej W. Rozycki
2002-01-30 20:02 ` Jason Gunthorpe
2002-01-31 12:17 ` Maciej W. Rozycki
2002-01-31 20:35 ` Jason Gunthorpe
2002-01-31 21:50 ` Maciej W. Rozycki
2002-02-01 6:44 ` Jason Gunthorpe
2002-02-01 8:55 ` Dominic Sweetman
2002-02-01 12:04 ` Maciej W. Rozycki
2002-02-01 9:52 ` Hartvig Ekner
2002-02-01 9:52 ` Hartvig Ekner
2002-02-01 12:01 ` Maciej W. Rozycki
2002-01-31 23:38 ` Alan Cox
2002-01-31 23:38 ` Alan Cox
2002-02-01 12:27 ` Maciej W. Rozycki
2002-02-02 12:09 ` Maciej W. Rozycki
2002-02-04 17:02 ` Ralf Baechle [this message]
2002-02-05 10:33 ` Maciej W. Rozycki
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