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From: Robert Hancock <hancockr@shaw.ca>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Document Linux's memory barriers
Date: Tue, 07 Mar 2006 19:10:00 -0600	[thread overview]
Message-ID: <440E2EE8.10708@shaw.ca> (raw)
In-Reply-To: <5NUSF-30Z-5@gated-at.bofh.it>

Alan Cox wrote:
> On Maw, 2006-03-07 at 22:24 +0100, Andi Kleen wrote:
>>> But on most arches those accesses do indeed seem to happen in-order.  On
>>> i386 and x86_64, it's a natural consequence of program store ordering.
>> Not true for reads on x86.
> 
> 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..

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/


  parent reply	other threads:[~2006-03-08  1:11 UTC|newest]

Thread overview: 61+ 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 [this message]
2006-03-08 11:35           ` Alan Cox
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 18:54     ` linux-os (Dick Johnson)
2006-03-07 19:06     ` Matthew Wilcox
2006-03-07 19:15       ` linux-os (Dick Johnson)
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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