Re: [Xen-devel] [PATCH net V2] xen-netback: don't move event pointer in TX credit timeout callback

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, May 15, 2014 at 02:40:58PM +0100, David Vrabel wrote:
> On 15/05/14 12:59, Wei Liu wrote:
> > ... otherwise the frontend will try to send TX event all the time, even
> > if no progress can be made. The pointer should only be advanced by the
> > routine that actually processes the ring (that is, xenvif_poll).
> 
> No it does not.  RING_FINAL_CHECK_FOR_REQUESTS() only advances the event
> index if the ring is empty.
> 
> This will also result in xenvif_up() failing to properly enable the event.
> 
> I think Jacek's bug may be that netback fails to call napi_complete()
> when credit is exceeded and there still outstanding requests on the
> from-guest ring and thus napi repeatedly polls.
> 

Correct. We should call napi_complete if this vif is rate limited.

Wei.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel