* Keir Fraser <[EMAIL PROTECTED]> wrote:
> On 16/3/07 08:54, "Ingo Molnar" <[EMAIL PROTECTED]> wrote:
>
> >> + prod = intf->in_prod;
> >> + mb();
> >> + BUG_ON((prod - cons) > sizeof(intf->in));
> >
> > such mb()'s are typically a sign of "i have no clear idea what SMP
> > serialization rules apply here, but something is needed because
> > otherwise it breaks" ?
>
> These mb()'s are pretty standard for lock-free producer/consumer
> rings. Write descriptor /then/ write the updated producer. Read the
> producer /then/ read any descriptors revealed by this new producer
> value.
then use rmb()/wmb(). Rarely does a ring protocol truly need mb().
Ingo
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