[PATCH] virtio: remove overzealous BUG_ON.

[Anthony Liguori]

Rusty Russell wrote:
> The 'disable_cb' callback is designed as an optimization to tell the host
> we don't need callbacks now.  As it is not reliable, the debug check is
> overzealous: it can happen on two CPUs at the same time.  Document this.
> 
> Even if it were reliable, the virtio_net driver doesn't disable
> callbacks on transmit so the START_USE/END_USE debugging reentrance
> protection can be easily tripped even on UP.
> 
> Thanks to Balaji Rao for the bug report and testing.

I think the printk() in start_xmit should be removed too (or at least 
rate limited).

Regards,

Anthony Liguori