From: Benjamin LaHaise <bcrl@kvack.org>
To: "Bryan O'Sullivan" <bos@pathscale.com>
Cc: Andrew Morton <akpm@osdl.org>, Andi Kleen <ak@suse.de>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Define wc_wmb, a write barrier for PCI write combining
Date: Sat, 25 Feb 2006 09:28:14 -0500 [thread overview]
Message-ID: <20060225142814.GB17844@kvack.org> (raw)
In-Reply-To: <1140841250.2587.33.camel@localhost.localdomain>
On Fri, Feb 24, 2006 at 08:20:50PM -0800, Bryan O'Sullivan wrote:
> On some platforms, a regular wmb() is not sufficient to guarantee that
> PCI writes have been flushed to the bus if write combining is in effect.
>
> This change introduces a new macro, wc_wmb(), that makes this guarantee.
>
> It does so by way of a new header file, <linux/system.h>. This header
> can be a site for oft-replicated code from <asm-*/system.h>, but isn't
> just yet.
>
> We also define a version of wc_wmb() with the required semantics
> on x86_64.
This does not do what you're trying to accomplish. sfence has no impact
on the flushing of the write combining buffers -- they're normally flushed
after a few cycles of no subsequent merges. If it is really necessary to
flush such a write, you will have to do a read from the target PCI device
(well, bus would do).
-ben
--
"Ladies and gentlemen, I'm sorry to interrupt, but the police are here
and they've asked us to stop the party." Don't Email: <dont@kvack.org>.
next prev parent reply other threads:[~2006-02-25 14:33 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-25 4:20 [PATCH] Define wc_wmb, a write barrier for PCI write combining Bryan O'Sullivan
2006-02-25 4:43 ` Andi Kleen
2006-02-25 7:34 ` Bryan O'Sullivan
2006-02-25 13:28 ` Andi Kleen
2006-02-25 17:20 ` Bryan O'Sullivan
2006-02-25 19:01 ` Bryan O'Sullivan
2006-02-28 17:44 ` Jesse Barnes
2006-02-28 17:50 ` Roland Dreier
2006-02-28 17:50 ` Jesse Barnes
2006-02-28 17:52 ` Bryan O'Sullivan
2006-02-28 17:59 ` Jesse Barnes
2006-02-25 14:28 ` Benjamin LaHaise [this message]
2006-02-25 17:11 ` Bryan O'Sullivan
2006-02-25 17:41 ` Benjamin LaHaise
2006-02-28 17:50 ` Bryan O'Sullivan
2006-02-28 17:58 ` Benjamin LaHaise
2006-02-28 18:20 ` Bryan O'Sullivan
2006-02-28 19:03 ` Benjamin LaHaise
2006-02-28 19:20 ` Bryan O'Sullivan
2006-02-28 19:33 ` Andi Kleen
2006-02-28 19:44 ` Bryan O'Sullivan
2006-03-01 19:20 ` Bryan O'Sullivan
2006-03-01 19:27 ` Andi Kleen
2006-03-01 19:43 ` Bryan O'Sullivan
2006-03-01 19:49 ` Andi Kleen
2006-03-01 20:05 ` Bryan O'Sullivan
2006-03-01 20:26 ` Benjamin LaHaise
2006-03-01 20:35 ` Bryan O'Sullivan
2006-02-28 19:34 ` Benjamin LaHaise
2006-02-28 18:22 ` Christopher Friesen
2006-02-28 10:01 ` Jes Sorensen
2006-02-28 15:42 ` Roland Dreier
2006-02-28 16:08 ` Jes Sorensen
2006-02-28 17:02 ` Roland Dreier
2006-02-28 17:13 ` Jesse Barnes
2006-02-28 17:20 ` Jes Sorensen
2006-03-01 8:16 ` Jeremy Higdon
2006-03-01 8:24 ` Jeremy Higdon
2006-02-28 17:11 ` Jesse Barnes
2006-02-28 17:57 ` Bryan O'Sullivan
2006-02-28 18:07 ` linux-os (Dick Johnson)
2006-02-28 18:24 ` Christopher Friesen
2006-03-01 10:45 ` Jes Sorensen
2006-03-01 17:04 ` Roland Dreier
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