Re: [patch 134/149] x86, paravirt: Add a global synchronization point for pvclock

[Jeremy Fitzhardinge]

On 07/14/2010 10:30 AM, H. Peter Anvin wrote:
> If gcc ever starts reordering volatile operations, including "asm
> volatile", the kernel will break, and will be unfixable.  Just about
> every single driver will break.  All over the kernel we're explicitly or
> implicitly making the assumption that volatile operations are strictly
> ordered by the compiler with respect to each other.
>   

Can you give an example?  All the cases I've seen rely on the ordering
properties of "memory" clobbers, which is sound.  (And volatile
variables are a completely unrelated issue, of course.)

    J
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