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

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Message-ID: <1328005476.26983.335.camel@zakaz.uk.xensource.com>
Date:	Tue, 31 Jan 2012 10:24:36 +0000
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Wei Liu <wei.liu2@...rix.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>
Subject: Re: [RFC PATCH V3 05/16] netback: add module get/put operations
 along with vif connect/disconnect.

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@...cle.com>
> Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> ---
>  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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