From: Roland Dreier <rdreier@cisco.com>
To: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: "Bryan O'Sullivan" <bos@pathscale.com>, Andi Kleen <ak@suse.de>,
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: Tue, 28 Feb 2006 09:50:48 -0800 [thread overview]
Message-ID: <ada7j7fl6dj.fsf@cisco.com> (raw)
In-Reply-To: <200602280944.32210.jbarnes@virtuousgeek.org> (Jesse Barnes's message of "Tue, 28 Feb 2006 09:44:31 -0800")
Jesse> I don't think it addresses the flushing issue you seem to
Jesse> be concerned about though. I don't know the exact
Jesse> semantics of sfence, but I think bcrl is likely right that
Jesse> it won't absolutely guarantee that your writes have hit the
Jesse> device before proceeding (though it may do that on some CPU
Jesse> implementations).
Yeah, I think that Bryan just wrote something different than what he
meant: there is no desire for wc_wmb() to make sure that writes via a
write-combining mapping have gone all the way to the device, any more
than a normal wmb() makes sure normal writes have gone all the way to
the device. All that wc_wmb() needs to do is make sure that writes
via a write-combining mapping don't get passed by later writes.
This does speak to the need for precise documentation though :)
- R.
next prev parent reply other threads:[~2006-02-28 17:51 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 [this message]
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
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