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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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.

> 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?


> +     }
>  
>       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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