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

H. Peter Anvin
2010-07-13T22:18:37Z

On 07/13/2010 11:21 AM, Jeremy Fitzhardinge wrote:
>
> "asm volatile"'s only real meaning is that it will not get elided if it
> appears its output is unused (assuming it is reachable at all). I don't
> think you can consider it having any meaningful effects on ordering.
>

Actually, I believe volatile operations (including asm volatile) are
strictly ordered *with respect to other volatile operations*. As such I
would think we'd want to keep the "memory" clobber here, to make it
strictly ordered with regards to *all* memory operations.

As for the concept in this patch, it's obviously the right thing, but as
Linus said elsewhere it's incomplete.

Conceptually:

Acked-by: H. Peter Anvin <hpa@zytor.com>

Unfortunately I can't write the productization patch right now since I
have a plane to catch in about an hour, but if noone beats me to it I'll
to it Thursday.

-hpa