MMIO and gcc re-ordering issue

[Benjamin Herrenschmidt]

On Tue, 2008-05-27 at 09:47 -0700, Linus Torvalds wrote:
> 
> __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).

Nah, asm volatile doesn't help, it does need the "memory" clobber too.

Cheers,
Ben.