From: Linus Torvalds Date: Tue, 27 May 2008 16:47:13 +0000 (-0700) Subject: x86: MMIO and gcc re-ordering issue X-Git-Tag: v2.6.27-rc1~1106^2~249^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c1f64a58003fd2efaa725a857e269a15f765791a;p=pandora-kernel.git x86: MMIO and gcc re-ordering issue On Tue, 27 May 2008, Linus Torvalds wrote: > > Expecting people to fix up all drivers is simply not going to happen. And > serializing things shouldn't be *that* expensive. People who cannot take > the expense can continue to use the magic __raw_writel() etc stuff. Of course, for non-x86, you kind of have to expect drivers to be well-behaved, so non-x86 can probably avoid this simply because there are less relevant drivers involved. Here's a UNTESTED patch for x86 that may or may not compile and work, and which serializes (on a compiler level) the IO accesses against regular memory accesses. __read[bwlq]()/__write[bwlq]() are not serialized with a :"memory" barrier, although since they still use "asm volatile" I suspect that i practice they are probably serial too. Did not look very closely at any generated code (only did a trivial test to see that the code looks *roughly* correct). Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed