diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2008-05-27 09:47:13 -0700 |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-06-02 12:29:31 +0200 |
commit | c1f64a58003fd2efaa725a857e269a15f765791a (patch) | |
tree | 68a09bddb1c16fbcc748df41ddca4edb4442cb56 /Documentation/cputopology.txt | |
parent | 1beee8dc8cf58e3f605bd7b34d7a39939be7d8d2 (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>
Diffstat (limited to 'Documentation/cputopology.txt')
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