netdev - RE: [PATCH net-next v4] Don't destroy the netdev until the vif is shut down

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Message-ID: <9AAE0902D5BC7E449B7C8E4E778ABCD010DCCE@AMSPEX01CL01.citrite.net>
Date:	Thu, 19 Sep 2013 11:55:37 +0000
From:	Paul Durrant <Paul.Durrant@...rix.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
CC:	Wei Liu <wei.liu2@...rix.com>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	David Vrabel <david.vrabel@...rix.com>
Subject: RE: [PATCH net-next v4] Don't destroy the netdev until the vif is
 shut down

> -----Original Message-----
> From: Ian Campbell [mailto:ian.campbell@...rix.com]
> Sent: 18 September 2013 17:25
> To: Paul Durrant
> Cc: Wei Liu; xen-devel@...ts.xen.org; netdev@...r.kernel.org; David Vrabel
> Subject: Re: [PATCH net-next v4] Don't destroy the netdev until the vif is
> shut down
> 
> On Wed, 2013-09-18 at 17:04 +0100, Paul Durrant wrote:
> > > -----Original Message-----
> > > From: Ian Campbell [mailto:ian.campbell@...rix.com]
> > > Sent: 18 September 2013 16:58
> > > To: Wei Liu
> > > Cc: Paul Durrant; xen-devel@...ts.xen.org; netdev@...r.kernel.org;
> David
> > > Vrabel
> > > Subject: Re: [PATCH net-next v4] Don't destroy the netdev until the vif is
> > > shut down
> > >
> > > On Wed, 2013-09-18 at 11:37 +0100, Wei Liu wrote:
> > > > On Tue, Sep 17, 2013 at 05:46:08PM +0100, Paul Durrant wrote:
> > > > > Without this patch, if a frontend cycles through states Closing
> > > > > and Closed (which Windows frontends need to do) then the netdev
> > > > > will be destroyed and requires re-invocation of hotplug scripts
> > > > > to restore state before the frontend can move to Connected. Thus
> > > > > when udev is not in use the backend gets stuck in InitWait.
> > > > >
> > > > > With this patch, the netdev is left alone whilst the backend is
> > > > > still online and is only de-registered and freed just prior to
> > > > > destroying the vif (which is also nicely symmetrical with the
> > > > > netdev allocation and registration being done during probe) so
> > > > > no re-invocation of hotplug scripts is required.
> > > > >
> > > > > Signed-off-by: Paul Durrant <paul.durrant@...rix.com>
> > > > > Cc: David Vrabel <david.vrabel@...rix.com>
> > > > > Cc: Wei Liu <wei.liu2@...rix.com>
> > > > > Cc: Ian Campbell <ian.campbell@...rix.com>
> > > >
> > > > Acked-by: Wei Liu <wei.liu2@...rix.com>
> > >
> > > yeah, looks good, thanks.
> > >
> > > Paul, did you test this with non-Windows frontends too? and do things
> > > like vif hot(un)plug still work?
> > >
> >
> > Ian,
> >
> > I tested with a debian (wheezy) PV guest but I didn't test unplug. I
> > cycled a windows frontend several times (which is how I spotted the
> > tx_irq thing), and shutdown and brought up both the debian and windows
> > guests several times. I can test unplug too if you'd like.
> 
> I don't think it needs to be a blocker for accepting this patch but it
> would be good to try it, it's the sort of area which historically gets
> broken by this sort of change.
> 

FWIW I just checked network-detach with a windows frontend and it worked ok.

  Paul