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

Jeremy Fitzhardinge
2010-07-14T17:34:19Z

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