Jesse Barnes wrote:
On Tuesday, March 7, 2006 10:30 am, David Howells wrote:
True, I suppose. I should make it clear that these accessor functions
imply memory barriers, if indeed they do, and that you should use them
rather than accessing I/O registers directly (at least, outside the
arch you should).
But they don't, that's why we have mmiowb().
I don't think that is why that function exists.. It's a no-op on most
architectures, even where you would need to be able to do write barriers
on IO accesses (i.e. x86_64 using CONFIG_UNORDERED_IO). I believe that
function is intended for a more limited special case.
I think any complete memory barrier description should document that
function as well as EXPLICITLY specifying whether or not the
readX/writeX, etc. functions imply barriers or not.
Btw, thanks for putting together this documentation, it's desperately
needed.
Seconded.. The fact that there's debate over what the rules even are
shows why this is needed so badly.
--
Robert Hancock Saskatoon, SK, Canada
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