From: Arjan van de Ven <arjan@infradead.org>
To: David Miller <davem@davemloft.net>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
linuxppc-dev@ozlabs.org, scottwood@freescale.com,
torvalds@linux-foundation.org, tpiepho@freescale.com,
alan@lxorguk.ukuu.org.uk
Subject: Re: MMIO and gcc re-ordering issue
Date: Mon, 26 May 2008 20:42:33 -0700 [thread overview]
Message-ID: <20080526204233.75b71bb8@infradead.org> (raw)
In-Reply-To: <20080526.192812.184590464.davem@davemloft.net>
On Mon, 26 May 2008 19:28:12 -0700 (PDT)
David Miller <davem@davemloft.net> wrote:
> From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Date: Tue, 27 May 2008 12:15:40 +1000
>
> > Some of them. USB comes to mind. I'd be happy to make it "the rule"
> > and document that MMIO vs. coherent access aren't implicitely
> > ordered. I would still keep them ordered on powerpc for a little
> > while tho until I'm happy enough with driver auditing.
> >
> > But heh, it's you who was telling me that it would be a bad
> > engineering decision and we had to make everybody look like x86 &
> > fully ordered :-) I decided to agree back then and stuck all those
> > nasty heavy barriers in the powerpc variants of readl/writel/...
>
> I still believe this.
>
> It's just another complicated thing for driver authors to get wrong.
> The other side of the coin is of course the cost.
>
> The only thing I am absolutely sure of is that we should make a
> decision fast, document it, and just stick to it.
... and try to find a way to test for it at runtime or compile time.
either via sparse or some fancy lockdep like "device store" thing?
If we can't test for it and it doesn't show up on x86 ... it'll just be
an eterrnal chase.
--
If you want to reach me at my work email, use arjan@linux.intel.com
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
next prev parent reply other threads:[~2008-05-27 3:42 UTC|newest]
Thread overview: 160+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-20 20:40 [PATCH] [POWERPC] Improve (in|out)_beXX() asm code Trent Piepho
2008-05-20 21:16 ` Benjamin Herrenschmidt
2008-05-20 21:38 ` Scott Wood
2008-05-20 22:02 ` Benjamin Herrenschmidt
2008-05-20 22:21 ` Trent Piepho
2008-05-20 22:15 ` Alan Cox
2008-05-20 22:35 ` Scott Wood
2008-05-20 22:39 ` David Miller
2008-05-20 22:43 ` Scott Wood
2008-05-20 22:53 ` David Miller
2008-05-23 4:24 ` Benjamin Herrenschmidt
2008-05-22 22:56 ` Trent Piepho
2008-05-23 12:36 ` MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code) Benjamin Herrenschmidt
2008-05-23 12:50 ` Benjamin Herrenschmidt
2008-05-23 21:14 ` Scott Wood
2008-05-23 22:47 ` Benjamin Herrenschmidt
2008-05-27 1:33 ` MMIO and gcc re-ordering issue Benjamin Herrenschmidt
2008-05-27 1:40 ` David Miller
2008-05-27 2:15 ` Benjamin Herrenschmidt
2008-05-27 2:28 ` David Miller
2008-05-27 3:39 ` Benjamin Herrenschmidt
2008-05-27 15:35 ` Linus Torvalds
2008-05-27 16:47 ` Linus Torvalds
2008-05-27 17:31 ` Linus Torvalds
2008-06-02 10:36 ` Ingo Molnar
2008-06-02 21:53 ` Benjamin Herrenschmidt
2008-05-27 21:12 ` Benjamin Herrenschmidt
2008-05-27 18:23 ` Trent Piepho
2008-05-27 18:33 ` Scott Wood
2008-05-27 21:10 ` Benjamin Herrenschmidt
2008-05-27 21:30 ` Linus Torvalds
2008-05-27 21:38 ` Alan Cox
2008-05-27 21:53 ` Matthew Wilcox
2008-05-27 21:46 ` Alan Cox
2008-05-27 22:02 ` Linus Torvalds
2008-05-27 21:59 ` Linus Torvalds
2008-05-27 21:38 ` Benjamin Herrenschmidt
2008-05-27 21:42 ` Matthew Wilcox
2008-05-27 22:17 ` Benjamin Herrenschmidt
2008-05-28 8:36 ` Haavard Skinnemoen
2008-05-29 11:05 ` Pantelis Antoniou
2008-05-30 1:13 ` Benjamin Herrenschmidt
2008-05-30 6:07 ` Haavard Skinnemoen
2008-05-30 7:24 ` Benjamin Herrenschmidt
2008-05-30 8:27 ` Haavard Skinnemoen
2008-05-30 9:22 ` Geert Uytterhoeven
2008-06-02 8:11 ` Haavard Skinnemoen
2008-06-02 15:48 ` Scott Wood
2008-06-03 7:46 ` Haavard Skinnemoen
2008-06-04 15:31 ` Linus Torvalds
2008-05-27 21:55 ` Linus Torvalds
2008-05-27 22:19 ` Benjamin Herrenschmidt
2008-05-29 7:10 ` Arnd Bergmann
2008-05-29 10:46 ` Alan Cox
2008-06-02 7:24 ` Russell King
2008-06-03 4:16 ` Nick Piggin
2008-06-03 4:32 ` Benjamin Herrenschmidt
2008-06-03 6:11 ` Nick Piggin
2008-06-03 6:48 ` Benjamin Herrenschmidt
2008-06-03 6:53 ` Paul Mackerras
2008-06-03 7:18 ` Nick Piggin
2008-06-03 14:47 ` Linus Torvalds
2008-06-03 18:47 ` Trent Piepho
2008-06-03 18:55 ` Matthew Wilcox
2008-06-03 19:57 ` Trent Piepho
2008-06-03 21:35 ` Matthew Wilcox
2008-06-03 21:58 ` Trent Piepho
2008-06-04 2:00 ` Nick Piggin
2008-06-03 19:07 ` Linus Torvalds
2008-06-04 2:05 ` Nick Piggin
2008-06-04 2:46 ` Linus Torvalds
2008-06-04 11:47 ` Alan Cox
2008-06-10 6:56 ` Nick Piggin
2008-06-10 17:41 ` Jesse Barnes
2008-06-10 18:10 ` James Bottomley
2008-06-10 19:05 ` Roland Dreier
2008-06-10 19:19 ` Jesse Barnes
2008-06-11 3:29 ` Nick Piggin
2008-06-11 3:40 ` Benjamin Herrenschmidt
2008-06-11 4:06 ` Nick Piggin
2008-06-11 16:07 ` Jesse Barnes
2008-06-12 11:27 ` Nick Piggin
2008-06-11 4:18 ` Paul Mackerras
2008-06-11 5:00 ` Nick Piggin
2008-06-11 5:13 ` Paul Mackerras
2008-06-11 5:35 ` Nick Piggin
2008-06-11 6:02 ` Nick Piggin
2008-06-12 12:14 ` Paul Mackerras
2008-06-12 13:08 ` Nick Piggin
2008-06-11 14:46 ` Linus Torvalds
2008-06-11 5:20 ` Paul Mackerras
2008-06-04 2:19 ` Nick Piggin
2008-06-03 19:43 ` Trent Piepho
2008-06-03 21:33 ` Matthew Wilcox
2008-06-03 21:44 ` Trent Piepho
2008-06-04 2:25 ` Nick Piggin
2008-06-04 6:39 ` Trent Piepho
2008-06-03 22:26 ` Benjamin Herrenschmidt
2008-05-27 3:42 ` Arjan van de Ven [this message]
2008-05-27 4:08 ` Roland Dreier
2008-05-27 4:20 ` Arjan van de Ven
2008-05-27 7:08 ` Benjamin Herrenschmidt
2008-05-27 15:50 ` Roland Dreier
2008-05-27 16:37 ` James Bottomley
2008-05-27 17:38 ` Roland Dreier
2008-05-27 17:53 ` James Bottomley
2008-05-27 18:07 ` Roland Dreier
2008-05-27 18:17 ` Roland Dreier
2008-05-27 21:23 ` Chris Friesen
2008-05-27 21:29 ` Roland Dreier
2008-05-27 23:04 ` Paul Mackerras
2008-05-27 21:11 ` Benjamin Herrenschmidt
2008-05-27 21:33 ` Roland Dreier
2008-05-27 22:13 ` Benjamin Herrenschmidt
2008-05-27 22:39 ` Roland Dreier
2008-05-29 14:47 ` Jes Sorensen
2008-05-29 15:01 ` James Bottomley
2008-05-30 9:36 ` Jes Sorensen
2008-05-30 17:21 ` Jesse Barnes
2008-05-31 7:57 ` Jeremy Higdon
2008-05-29 21:40 ` Benjamin Herrenschmidt
2008-05-29 21:48 ` Trent Piepho
2008-05-29 22:05 ` Benjamin Herrenschmidt
2008-05-30 1:53 ` Trent Piepho
2008-05-29 21:53 ` Jesse Barnes
2008-05-30 9:39 ` Jes Sorensen
2008-05-30 9:48 ` Jes Sorensen
2008-05-31 8:14 ` Pavel Machek
2008-06-02 9:48 ` Jes Sorensen
2008-05-29 22:06 ` Roland Dreier
2008-05-29 22:25 ` Trent Piepho
2008-05-30 3:56 ` Paul Mackerras
2008-05-31 7:52 ` Jeremy Higdon
2008-06-02 9:56 ` Jes Sorensen
2008-06-02 21:02 ` Jeremy Higdon
2008-06-03 4:33 ` Nick Piggin
2008-06-03 8:15 ` Jeremy Higdon
2008-06-03 8:19 ` Nick Piggin
2008-06-03 8:45 ` Jeremy Higdon
2008-06-03 16:52 ` Jesse Barnes
2008-06-05 8:40 ` Jes Sorensen
2008-06-05 8:43 ` Benjamin Herrenschmidt
2008-06-12 15:07 ` Matthew Wilcox
2008-06-13 0:07 ` Benjamin Herrenschmidt
2008-05-31 8:04 ` Pavel Machek
2008-05-27 8:24 ` Alan Cox
2008-05-27 15:28 ` Jonathan Corbet
2008-05-20 22:55 ` [PATCH] [POWERPC] Improve (in|out)_beXX() asm code Trent Piepho
2008-05-21 14:01 ` Benjamin Herrenschmidt
2008-05-20 22:00 ` Trent Piepho
2008-05-21 14:00 ` Benjamin Herrenschmidt
2008-05-21 19:44 ` Trent Piepho
2008-05-21 20:41 ` Benjamin Herrenschmidt
2008-05-20 22:00 ` Andreas Schwab
2008-05-20 22:11 ` Trent Piepho
2008-05-20 22:47 ` Andreas Schwab
2008-05-20 23:14 ` Trent Piepho
2008-05-21 8:03 ` Andreas Schwab
2008-05-21 20:25 ` Trent Piepho
2008-05-27 23:48 ` [PATCH V2] [POWERPC] Improve (in|out)_[bl]eXX() " Trent Piepho
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