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Re: MMIO and gcc re-ordering issue

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From: Alan Cox <alan@...>
To: David Miller <davem@...>
Cc: <benh@...>, <linux-arch@...>, <scottwood@...>, <linuxppc-dev@...>, <linux-kernel@...>, <torvalds@...>, <tpiepho@...>
Subject: Re: MMIO and gcc re-ordering issue
Date: Tuesday, May 27, 2008 - 4:24 am

> It's just another complicated thing for driver authors to get wrong.

It's unfortunate that the __read/___write versions have other different
semantics. The default should definitely be ordered but having un-ordered
ones as an option would be good for zapping the hot paths that matter.

Most I/O paths aren't even worth the thinking time for non-ordered I/O.

Alan
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[PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 4:40 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Andreas Schwab, (Tue May 20, 6:00 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 6:11 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Andreas Schwab, (Tue May 20, 6:47 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 7:14 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Andreas Schwab, (Wed May 21, 4:03 am)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Wed May 21, 4:25 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Tue May 20, 5:16 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 6:00 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Wed May 21, 10:00 am)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Wed May 21, 3:44 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Wed May 21, 4:41 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Scott Wood, (Tue May 20, 5:38 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Alan Cox, (Tue May 20, 6:15 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Scott Wood, (Tue May 20, 6:35 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 6:55 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Wed May 21, 10:01 am)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, David Miller, (Tue May 20, 6:39 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Scott Wood, (Tue May 20, 6:43 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, David Miller, (Tue May 20, 6:53 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Fri May 23, 12:24 am)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Thu May 22, 6:56 pm)
MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Mon May 26, 9:33 pm)
Re: MMIO and gcc re-ordering issue, Jonathan Corbet, (Tue May 27, 11:28 am)
Re: MMIO and gcc re-ordering issue, David Miller, (Mon May 26, 9:40 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Mon May 26, 10:15 pm)
Re: MMIO and gcc re-ordering issue, David Miller, (Mon May 26, 10:28 pm)
Re: MMIO and gcc re-ordering issue, Alan Cox, (Tue May 27, 4:24 am)
Re: MMIO and gcc re-ordering issue, Arjan van de Ven, (Mon May 26, 11:42 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 3:08 am)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 11:50 am)
Re: MMIO and gcc re-ordering issue, Pavel Machek, (Sat May 31, 4:04 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 5:11 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 5:33 pm)
Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Thu May 29, 10:47 am)
Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Sat May 31, 3:52 am)
Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Mon Jun 2, 5:56 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 12:33 am)
Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Tue Jun 3, 12:52 pm)
Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Thu Jun 5, 4:40 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu Jun 5, 4:43 am)
Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Thu Jun 12, 11:07 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu Jun 12, 8:07 pm)
Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Tue Jun 3, 4:15 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 4:19 am)
Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Tue Jun 3, 4:45 am)
Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Mon Jun 2, 5:02 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Thu May 29, 6:06 pm)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Thu May 29, 6:25 pm)
Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Thu May 29, 11:56 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu May 29, 5:40 pm)
Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Fri May 30, 5:48 am)
Re: MMIO and gcc re-ordering issue, Pavel Machek, (Sat May 31, 4:14 am)
Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Mon Jun 2, 5:48 am)
Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Thu May 29, 5:53 pm)
Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Fri May 30, 5:39 am)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Thu May 29, 5:48 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu May 29, 6:05 pm)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Thu May 29, 9:53 pm)
Re: MMIO and gcc re-ordering issue, James Bottomley, (Thu May 29, 11:01 am)
Re: MMIO and gcc re-ordering issue, Jes Sorensen, (Fri May 30, 5:36 am)
Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Fri May 30, 1:21 pm)
Re: MMIO and gcc re-ordering issue, Jeremy Higdon, (Sat May 31, 3:57 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 6:13 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 6:39 pm)
Re: MMIO and gcc re-ordering issue, James Bottomley, (Tue May 27, 12:37 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 1:38 pm)
Re: MMIO and gcc re-ordering issue, James Bottomley, (Tue May 27, 1:53 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 2:07 pm)
Re: MMIO and gcc re-ordering issue, Chris Friesen, (Tue May 27, 5:23 pm)
Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Tue May 27, 7:04 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 5:29 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 2:17 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue May 27, 12:08 am)
Re: MMIO and gcc re-ordering issue, Arjan van de Ven, (Tue May 27, 12:20 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Mon May 26, 11:39 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 11:35 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 5:10 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 5:30 pm)
Re: MMIO and gcc re-ordering issue, Alan Cox, (Tue May 27, 5:38 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 5:59 pm)
Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue May 27, 5:53 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 6:02 pm)
Re: MMIO and gcc re-ordering issue, Alan Cox, (Tue May 27, 5:46 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 5:38 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 5:55 pm)
Re: MMIO and gcc re-ordering issue, Russell King, (Mon Jun 2, 3:24 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 12:16 am)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 3:43 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue Jun 3, 6:26 pm)
Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue Jun 3, 5:33 pm)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 5:44 pm)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 10:25 pm)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Wed Jun 4, 2:39 am)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue Jun 3, 10:47 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 10:19 pm)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 2:47 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue Jun 3, 3:07 pm)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 10, 2:56 am)
Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Wed Jun 11, 1:20 am)
Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Wed Jun 11, 12:18 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Wed Jun 11, 1:00 am)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Wed Jun 11, 10:46 am)
Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Wed Jun 11, 1:13 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Wed Jun 11, 1:35 am)
Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Thu Jun 12, 8:14 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Thu Jun 12, 9:08 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Wed Jun 11, 2:02 am)
Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Tue Jun 10, 1:41 pm)
Re: MMIO and gcc re-ordering issue, James Bottomley, (Tue Jun 10, 2:10 pm)
Re: MMIO and gcc re-ordering issue, Roland Dreier, (Tue Jun 10, 3:05 pm)
Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Tue Jun 10, 3:19 pm)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 10, 11:29 pm)
Re: MMIO and gcc re-ordering issue, Jesse Barnes, (Wed Jun 11, 12:07 pm)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Thu Jun 12, 7:27 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue Jun 10, 11:40 pm)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Wed Jun 11, 12:06 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 10:05 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue Jun 3, 10:46 pm)
Re: MMIO and gcc re-ordering issue, Alan Cox, (Wed Jun 4, 7:47 am)
Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue Jun 3, 2:55 pm)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 3:57 pm)
Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue Jun 3, 5:35 pm)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue Jun 3, 5:58 pm)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 10:00 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue Jun 3, 12:32 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 2:11 am)
Re: MMIO and gcc re-ordering issue, Paul Mackerras, (Tue Jun 3, 2:53 am)
Re: MMIO and gcc re-ordering issue, Nick Piggin, (Tue Jun 3, 3:18 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue Jun 3, 2:48 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 6:19 pm)
Re: MMIO and gcc re-ordering issue, Arnd Bergmann, (Thu May 29, 3:10 am)
Re: MMIO and gcc re-ordering issue, Alan Cox, (Thu May 29, 6:46 am)
Re: MMIO and gcc re-ordering issue, Matthew Wilcox, (Tue May 27, 5:42 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 6:17 pm)
Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Wed May 28, 4:36 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Thu May 29, 9:13 pm)
Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Fri May 30, 2:07 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Fri May 30, 3:24 am)
Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Fri May 30, 4:27 am)
Re: MMIO and gcc re-ordering issue, Geert Uytterhoeven, (Fri May 30, 5:22 am)
Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Mon Jun 2, 4:11 am)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Wed Jun 4, 11:31 am)
Re: MMIO and gcc re-ordering issue, Scott Wood, (Mon Jun 2, 11:48 am)
Re: MMIO and gcc re-ordering issue, Haavard Skinnemoen, (Tue Jun 3, 3:46 am)
Re: MMIO and gcc re-ordering issue, Pantelis Antoniou, (Thu May 29, 7:05 am)
Re: MMIO and gcc re-ordering issue, Trent Piepho, (Tue May 27, 2:23 pm)
Re: MMIO and gcc re-ordering issue, Scott Wood, (Tue May 27, 2:33 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 12:47 pm)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Tue May 27, 5:12 pm)
Re: MMIO and gcc re-ordering issue, Linus Torvalds, (Tue May 27, 1:31 pm)
Re: MMIO and gcc re-ordering issue, Ingo Molnar, (Mon Jun 2, 6:36 am)
Re: MMIO and gcc re-ordering issue, Benjamin Herrenschmidt, (Mon Jun 2, 5:53 pm)
MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve (in..., Benjamin Herrenschmidt, (Fri May 23, 8:36 am)
Re: MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve..., Benjamin Herrenschmidt, (Fri May 23, 8:50 am)
Re: MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve..., Scott Wood, (Fri May 23, 5:14 pm)
Re: MMIO and gcc re-ordering (Was: [PATCH] [POWERPC] Improve..., Benjamin Herrenschmidt, (Fri May 23, 6:47 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Benjamin Herrenschmidt, (Tue May 20, 6:02 pm)
Re: [PATCH] [POWERPC] Improve (in|out)_beXX() asm code, Trent Piepho, (Tue May 20, 6:21 pm)