Re: [Xen-devel] [PATCH 3/8] netback: get/put module along with vif connect/disconnect

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Feb 15, 2013 at 04:00:04PM +0000, Wei Liu wrote:
> If there is vif running and user unloads netback, guest's network interface
> just mysteriously stops working. So we need to prevent unloading netback
> module if there is vif running.
> 
> The disconnect function of vif may get called by the generic framework even
> before vif connects, so thers is an extra check on whether we actually need to
> put module when disconnecting a vif.

Ah, I think this patch should come before the "netback: add module unload 
function"

> 
> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  drivers/net/xen-netback/interface.c |   18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/xen-netback/interface.c 
> b/drivers/net/xen-netback/interface.c
> index 221f426..db638e1 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -314,6 +314,8 @@ 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;
> @@ -341,6 +343,7 @@ int xenvif_connect(struct xenvif *vif, unsigned long 
> tx_ring_ref,
>  err_unmap:
>       xen_netbk_unmap_frontend_rings(vif);
>  err:
> +     module_put(THIS_MODULE);
>       return err;
>  }
>  
> @@ -358,18 +361,31 @@ void xenvif_carrier_off(struct xenvif *vif)
>  
>  void xenvif_disconnect(struct xenvif *vif)
>  {
> +     /*
> +      * This function may get called even before vif connets, set

connects

> +      * need_module_put if vif->irq != 0, which means vif has
> +      * already connected, we should call module_put to balance the
> +      * previous __module_get.
> +      */
> +     int need_module_put = 0;
> +
>       if (netif_carrier_ok(vif->dev))
>               xenvif_carrier_off(vif);
>  
>       atomic_dec(&vif->refcnt);
>       wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0);
>  
> -     if (vif->irq)
> +     if (vif->irq) {
>               unbind_from_irqhandler(vif->irq, vif);
> +             need_module_put = 1;
> +     }
>  
>       unregister_netdev(vif->dev);
>  
>       xen_netbk_unmap_frontend_rings(vif);
>  
>       free_netdev(vif->dev);
> +
> +     if (need_module_put)
> +             module_put(THIS_MODULE);
>  }
> -- 
> 1.7.10.4
> 

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