Re: [Xen-devel] [PATCH net-next] xen-netback: stop vif thread spinning if frontend is unresponsive

[David Laight <David.Laight@xxxxxxxxxx>]

> From: David Miller
...
> > -   if (!npo.copy_prod)
> > +   if (!npo.copy_prod) {
> > +           if (ring_full)
> > +                   vif->rx_queue_stopped = true;
> >             goto done;
> > +   }
> > +
> > +   vif->rx_queue_stopped = false;
> 
> And then you can code this as:
> 
>       vif->rx_queue_stopped = (!npo.copy_prod && ring_full);
>       if (!npo.copy_prod)
>               goto done;

Which isn't quite the same...
1) It always writes vif->rx_queue_stopped, the old code could
   leave it unchanged.
2) If 'npo' is global then the compiler can't assume that 'vif'
   doesn't alias it so may have to re-read it following the
   write to 'vif->rx_queue_stopped'.

        David




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