From: Jesse Barnes <jbarnes@sgi.com>
To: Keith Owens <kaos@ocs.com.au>
Cc: David Mosberger <davidm@hpl.hp.com>, Dan Maas <dmaas@dcine.com>,
linux-kernel@vger.kernel.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Ben Collins <bcollins@debian.org>
Subject: Re: readl/writel and memory barriers
Date: Tue, 19 Feb 2002 14:17:04 -0800 [thread overview]
Message-ID: <20020219141704.B1510654@sgi.com> (raw)
In-Reply-To: <20020219103506.A1511175@sgi.com> <13997.1014156337@ocs3.intra.ocs.com.au>
In-Reply-To: <13997.1014156337@ocs3.intra.ocs.com.au>
On Wed, Feb 20, 2002 at 09:05:37AM +1100, Keith Owens wrote:
> On Tue, 19 Feb 2002 10:35:06 -0800,
> Jesse Barnes <jbarnes@sgi.com> wrote:
> >Making a variable volatile doesn't guarantee that the compiler won't
> >reorder references to it, AFAIK.
>
> Ignoring the issue of hardware that reorders I/O, volatile accesses
> must not be reordered by the compiler. From a C9X draft (1999, anybody
> have the current C standard online?) :-
Of course volatile references must be ordered wrt each other, but a
reference to a volatile doesn't preclude the compiler from moving it
above or below accesses to other variables. That is, it doesn't act
as an optimization barrier. Sound right? I guess I'm getting a
little off-topic here...
Jesse
next prev parent reply other threads:[~2002-02-19 22:17 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-02-19 1:45 readl/writel and memory barriers Dan Maas
2002-02-19 9:31 ` Alan Cox
2002-02-19 17:10 ` David Mosberger
2002-02-19 18:35 ` Jesse Barnes
2002-02-19 19:33 ` David Mosberger
2002-02-19 19:42 ` Jesse Barnes
2002-02-19 20:11 ` Dan Maas
2002-02-19 20:23 ` Jesse Barnes
2002-02-19 22:05 ` Keith Owens
2002-02-19 22:17 ` Jesse Barnes [this message]
2002-02-21 0:29 ` Randy.Dunlap
2002-02-23 4:48 ` Daniel Phillips
2002-02-25 16:19 ` Randy.Dunlap
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