Re: [Xen-devel] [RFC PATCH V3 05/16] netback: add module get/put operations along with vif connect/disconnect.

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, 2012-01-31 at 10:24 +0000, Ian Campbell wrote:
> On Mon, 2012-01-30 at 14:45 +0000, Wei Liu wrote:
> > If there is vif running and user unloads netback, it will certainly
> > cause problems -- guest's network interface just mysteriously stops
> > working.
> 
> This seems like a bug fix for  02/16 "netback: add module unload
> function". Please could you fold back such fixes where appropriate? I
> think there's a handful of these sorts of patches in the series.
> 

Sure.

> > v2: fix module_put path
> > 
> > disconnect function may get called by the generic framework even
> > before vif connects.
> > 
> > Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > ---
> >  drivers/net/xen-netback/interface.c |   11 ++++++++++-
> >  1 files changed, 10 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/net/xen-netback/interface.c 
> > b/drivers/net/xen-netback/interface.c
> > index dfc04f8..7914f60 100644
> > --- a/drivers/net/xen-netback/interface.c
> > +++ b/drivers/net/xen-netback/interface.c
> > @@ -323,6 +323,8 @@ int xenvif_connect(struct xenvif *vif, unsigned long 
> > tx_ring_ref,
> >     if (vif->irq)
> >             return 0;
> >  
> > +   __module_get(THIS_MODULE);
> > +
> >     err = xen_netbk_map_frontend_rings(vif, tx_ring_ref, rx_ring_ref);
> >     if (err < 0)
> >             goto err;
> > @@ -372,12 +374,14 @@ err_unbind:
> >  err_unmap:
> >     xen_netbk_unmap_frontend_rings(vif);
> >  err:
> > +   module_put(THIS_MODULE);
> >     return err;
> >  }
> >  
> >  void xenvif_disconnect(struct xenvif *vif)
> >  {
> >     struct net_device *dev = vif->dev;
> > +   int need_module_put = 0;
> >  
> >     if (netif_carrier_ok(dev)) {
> >             rtnl_lock();
> > @@ -397,12 +401,17 @@ void xenvif_disconnect(struct xenvif *vif)
> >  
> >     del_timer_sync(&vif->credit_timeout);
> >  
> > -   if (vif->irq)
> > +   if (vif->irq) {
> >             unbind_from_irqhandler(vif->irq, vif);
> > +           need_module_put = 1;
> 
> This seems like a slightly odd condition. Why is the put not
> unconditional?
> 

This is what I observed. The framework will call disconnect
unconditionally in the cleanup phase. If the frontend fails to
initialize, the connect function will not get called, so there lacks a
corresponding module_get().


Wei.

> 
> > +   }
> >  
> >     unregister_netdev(vif->dev);
> >  
> >     xen_netbk_unmap_frontend_rings(vif);
> >  
> >     free_netdev(vif->dev);
> > +
> > +   if (need_module_put)
> > +           module_put(THIS_MODULE);
> >  }
> 
> 



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