From: "Bryan O'Sullivan" <bos@pathscale.com>
To: Andi Kleen <ak@suse.de>
Cc: Andrew Morton <akpm@osdl.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Define wc_wmb, a write barrier for PCI write combining
Date: Fri, 24 Feb 2006 23:34:53 -0800 [thread overview]
Message-ID: <1140852894.2587.43.camel@localhost.localdomain> (raw)
In-Reply-To: <200602250543.22421.ak@suse.de>
On Sat, 2006-02-25 at 05:43 +0100, Andi Kleen wrote:
> On Saturday 25 February 2006 05:20, 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.
>
> On what platforms?
On x86_64 in particular, if CONFIG_UNORDERED_IO is defined. Regular
wmb() is implemented as a compiler memory barrier then, which isn't
sufficient for PCI write combining.
> linux/system.h looks unnatural to me.
I used this for symmetry with <asm/system.h> where other barriers are
defined. It could obviously go into io.h instead, since it's an
MMIO-related barrier, but I didn't want to separate it from other
barriers.
If you have a location you'd prefer, please let me know.
> > We also define a version of wc_wmb() with the required semantics
> > on x86_64.
>
> Leaving i386 out in the cold?
Looks like it should be defined there, too, something like this perhaps:
#define wc_wmb() alternative("lock; addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)
Does that look right?
<b
next prev parent reply other threads:[~2006-02-25 7:34 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1140852894.2587.43.camel@localhost.localdomain \
--to=bos@pathscale.com \
--cc=ak@suse.de \
--cc=akpm@osdl.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).