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    SubjectRe: [patch 21/26] Xen-paravirt_ops: Use the hvc console infrastructure for Xen console

    * Jeremy Fitzhardinge <jeremy@goop.org> wrote:

    > Implement a Xen back-end for hvc console.

    > + cons = intf->out_cons;
    > + prod = intf->out_prod;
    > + mb();
    > + BUG_ON((prod - cons) > sizeof(intf->out));
    > +
    > + while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
    > + intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
    > +
    > + wmb();
    > + intf->out_prod = prod;

    > + 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" ?

    Ingo
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