Re: Use of barriers in pvclock ABI

[Avi Kivity]

Gerd Hoffmann wrote:
>   Hi,
>
>   
> > However, the pvclock_clocksource_read() implementation is
> > over-engineered, because it checks for an odd version and uses very
> > strong rmb() barriers (which generates either an "lfence" or "lock add
> > $0, (%esp)").
> >
> > If we're happy to guarantee as an ABI issue that the record will never
> > be updated cross-cpu, then we can make the barriers simply barrier() and
> > just check for (src->version != dst->version).
> >
> > Is that OK with you, or do you want to leave open the possibility of
> > doing cross-cpu time updates?
> >     
>
> Due to the TSC being involved here I don't expect cross-cpu time updates
> will ever happen.  IMHO it is fine to change that.
>
>   

I agree.  And if we ever feel the need, we can allocate a feature bit 
for it.

--
error compiling committee.c: too many arguments to function

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