From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Robert Hancock <hancockr@shaw.ca>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Document Linux's memory barriers
Date: Wed, 08 Mar 2006 11:35:13 +0000 [thread overview]
Message-ID: <1141817713.7605.9.camel@localhost.localdomain> (raw)
In-Reply-To: <440E2EE8.10708@shaw.ca>
On Maw, 2006-03-07 at 19:10 -0600, Robert Hancock wrote:
> Alan Cox wrote:
> > You must have a strange kernel Andi. Mine marks them as volatile
> > unsigned char * references.
>
> Well, that and the fact that IO memory should be mapped as uncacheable
> in the MTRRs should ensure that readl and writel won't be reordered on
> i386 and x86_64.. except in the case where CONFIG_UNORDERED_IO is
> enabled on x86_64 which can reorder writes since it uses nontemporal
> stores..
You need both
real/writel need the volatile to stop gcc removing/reordering the
accesses at compiler level, and the mtrr/pci bridge stuff then deals
with bus level ordering for that CPU.
next prev parent reply other threads:[~2006-03-08 11:29 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <5NONi-2hp-3@gated-at.bofh.it>
[not found] ` <5NOtZ-1FO-27@gated-at.bofh.it>
[not found] ` <5NPgs-2Rw-37@gated-at.bofh.it>
[not found] ` <5NPq4-34a-23@gated-at.bofh.it>
2006-03-08 0:22 ` [PATCH] Document Linux's memory barriers Robert Hancock
[not found] ` <5NQ2U-462-29@gated-at.bofh.it>
[not found] ` <5NRLg-6LJ-31@gated-at.bofh.it>
[not found] ` <5NRUR-6Yo-11@gated-at.bofh.it>
[not found] ` <5NUSF-30Z-5@gated-at.bofh.it>
2006-03-08 1:10 ` Robert Hancock
2006-03-08 11:35 ` Alan Cox [this message]
2006-03-08 14:55 ` Andi Kleen
2006-03-07 23:17 Chuck Ebbert
2006-03-08 0:15 ` David S. Miller
2006-03-08 0:24 ` Roberto Nibali
-- strict thread matches above, loose matches on Subject: below --
2006-03-07 17:40 David Howells
2006-03-07 10:34 ` Andi Kleen
2006-03-07 18:30 ` David Howells
2006-03-07 11:13 ` Andi Kleen
2006-03-07 19:24 ` David Howells
2006-03-07 19:46 ` Stephen Hemminger
2006-03-07 18:46 ` Jesse Barnes
2006-03-07 19:23 ` Bryan O'Sullivan
2006-03-07 11:57 ` Andi Kleen
2006-03-07 20:01 ` Jesse Barnes
2006-03-07 21:14 ` Bryan O'Sullivan
2006-03-07 21:24 ` Andi Kleen
2006-03-08 0:36 ` Alan Cox
2006-03-08 0:35 ` Alan Cox
2006-03-07 17:47 ` Stephen Hemminger
2006-03-07 18:40 ` Alan Cox
2006-03-07 18:54 ` linux-os (Dick Johnson)
2006-03-07 19:06 ` Matthew Wilcox
2006-03-07 19:15 ` linux-os (Dick Johnson)
2006-03-09 11:26 ` Sergei Organov
2006-03-07 19:33 ` Alan Cox
2006-03-07 20:09 ` David Howells
2006-03-08 0:32 ` Alan Cox
2006-03-08 8:25 ` Duncan Sands
2006-03-08 22:06 ` Paul Mackerras
2006-03-08 22:24 ` David S. Miller
2006-03-08 22:31 ` Linus Torvalds
2006-03-08 22:42 ` Alan Cox
2006-03-08 2:07 ` Nick Piggin
2006-03-08 3:10 ` Paul Mackerras
2006-03-08 3:30 ` Linus Torvalds
2006-03-08 12:34 ` David Howells
2006-03-08 16:40 ` Bryan O'Sullivan
2006-03-08 7:41 ` Nick Piggin
2006-03-08 13:19 ` David Howells
2006-03-08 21:49 ` Paul Mackerras
2006-03-08 22:05 ` Alan Cox
2006-03-10 0:49 ` H. Peter Anvin
2006-03-08 16:18 ` Pavel Machek
2006-03-08 20:16 ` David Howells
2006-03-08 22:01 ` Alan Cox
2006-03-09 11:41 ` David Howells
2006-03-09 12:28 ` Alan Cox
2006-03-09 13:02 ` David Howells
2006-03-09 16:32 ` Linus Torvalds
2006-03-09 17:39 ` David Howells
2006-03-09 17:54 ` Linus Torvalds
2006-03-09 17:56 ` Linus Torvalds
2006-03-08 16:26 ` Christoph Lameter
2006-03-08 17:35 ` David Howells
2006-03-08 17:46 ` Christoph Lameter
2006-03-08 17:59 ` Alan Cox
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