Re: [PATCH 1/5] Add a global synchronization point for pvclock

[Avi Kivity]

On 04/17/2010 09:48 PM, Avi Kivity wrote:
> > +static u64 last_value = 0;
>
> Needs to be atomic64_t.
>
> > +
> >   cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
> >   {
> >       struct pvclock_shadow_time shadow;
> >       unsigned version;
> >       cycle_t ret, offset;
> > +    u64 last;
> >
> >
> > +    do {
> > +        last = last_value;
>
> Otherwise, this assignment can see a partial update.

On a 32-bit guest, that is.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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