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

[Ingo Molnar <mingo@xxxxxxx>]

* Jeremy Fitzhardinge <jeremy@xxxxxxxx> 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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