Re: [Xen-devel] [PATCH net-next 2/2] xen-netback: handle frontends that fail to transition through Closing

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: David Vrabel
> Sent: 20 September 2013 14:39
> To: Wei Liu
> Cc: Paul Durrant; netdev@xxxxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; Ian
> Campbell
> Subject: Re: [PATCH net-next 2/2] xen-netback: handle frontends that fail to
> transition through Closing
> 
> On 20/09/13 14:34, Wei Liu wrote:
> > On Fri, Sep 20, 2013 at 01:56:31PM +0100, Paul Durrant wrote:
> >> Some old Windows frontends fail to transition through the xenbus Closing
> >> state and move directly from Connected to Closed. Handle this case
> properly.
> >>
> >> --- a/drivers/net/xen-netback/xenbus.c
> >> +++ b/drivers/net/xen-netback/xenbus.c
> >> @@ -265,6 +265,8 @@ static void frontend_changed(struct
> xenbus_device *dev,
> >>            break;
> >>
> >>    case XenbusStateClosed:
> >> +          if (dev->state == XenbusStateConnected)
> >> +                  disconnect_backend(dev);
> >
> > Could you please add a comment above this change stating that this is a
> > workaround for some old frontend that we cannot fix / upgrade.
> 
> Handling frontend CONNECTED -> CLOSED is a sensible thing for a backend
> to do regardless of whether there are old frontends that do this or not.
> 

Agreed, but probably still worth the comment in case someone gets the wrong 
idea.

  Paul

> > We would still like to later frontend goes through the normal connected
> > -> closing -> closed path.
> 
> This should be documented as a full description of the two state
> machines in public/io/netif.h in Xen.  Not scattered about in comments
> in a particular backend implementation.
> 
> David

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