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authorLinus Torvalds <torvalds@linux-foundation.org>2008-05-27 09:47:13 -0700
committerIngo Molnar <mingo@elte.hu>2008-06-02 12:29:31 +0200
commitc1f64a58003fd2efaa725a857e269a15f765791a (patch)
tree68a09bddb1c16fbcc748df41ddca4edb4442cb56 /Documentation/zh_CN
parent1beee8dc8cf58e3f605bd7b34d7a39939be7d8d2 (diff)
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 <mingo@elte.hu>
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