netdev - Re: [PATCH net-next 1/2] xen-netback: add a vif-is-connected flag

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Date:	Fri, 20 Sep 2013 14:31:06 +0100
From:	Wei Liu <wei.liu2@...rix.com>
To:	Paul Durrant <paul.durrant@...rix.com>
CC:	<netdev@...r.kernel.org>, <xen-devel@...ts.xen.org>,
	David Vrabel <david.vrabel@...rix.com>,
	Wei Liu <wei.liu2@...rix.com>,
	Ian Campbell <ian.campbell@...rix.com>
Subject: Re: [PATCH net-next 1/2] xen-netback: add a vif-is-connected flag

On Fri, Sep 20, 2013 at 01:56:30PM +0100, Paul Durrant wrote:
> Having applied my patch to separate vif disconnect and free, I ran into a
> BUG when testing resume from S3 with a Windows frontend because the vif task
> pointer was not cleared by xenvif_disconnect() and so a double call to this
> function tries to stop the thread twice.
> Rather than applying a point fix for that issue it seems better to introduce
> a boolean to indicate whether the vif is connected or not such that repeated
> calls to either xenvif_connect() or xenvif_disconnect() behave appropriately.
> 
> 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>

Reasonable change.

Acked-by: Wei Liu <wei.liu2@...rix.com>

Thanks
Wei.

> ---
>  drivers/net/xen-netback/common.h    |    1 +
>  drivers/net/xen-netback/interface.c |   24 +++++++++++++-----------
>  2 files changed, 14 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
> index 5715318..860d92c 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -169,6 +169,7 @@ struct xenvif {
>  
>  	/* Miscellaneous private stuff. */
>  	struct net_device *dev;
> +	bool connected;
>  };
>  
>  static inline struct xenbus_device *xenvif_to_xenbus_device(struct xenvif *vif)
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index 01bb854..94b47f5 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -366,7 +366,7 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
>  	int err = -ENOMEM;
>  
>  	/* Already connected through? */
> -	if (vif->tx_irq)
> +	if (vif->connected)
>  		return 0;
>  
>  	err = xenvif_map_frontend_rings(vif, tx_ring_ref, rx_ring_ref);
> @@ -425,6 +425,7 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
>  
>  	wake_up_process(vif->task);
>  
> +	vif->connected = 1;
>  	return 0;
>  
>  err_rx_unbind:
> @@ -453,23 +454,24 @@ void xenvif_carrier_off(struct xenvif *vif)
>  
>  void xenvif_disconnect(struct xenvif *vif)
>  {
> +	if (!vif->connected)
> +		return;
> +
>  	if (netif_carrier_ok(vif->dev))
>  		xenvif_carrier_off(vif);
>  
> -	if (vif->tx_irq) {
> -		if (vif->tx_irq == vif->rx_irq)
> -			unbind_from_irqhandler(vif->tx_irq, vif);
> -		else {
> -			unbind_from_irqhandler(vif->tx_irq, vif);
> -			unbind_from_irqhandler(vif->rx_irq, vif);
> -		}
> -		vif->tx_irq = 0;
> +	if (vif->tx_irq == vif->rx_irq)
> +		unbind_from_irqhandler(vif->tx_irq, vif);
> +	else {
> +		unbind_from_irqhandler(vif->tx_irq, vif);
> +		unbind_from_irqhandler(vif->rx_irq, vif);
>  	}
>  
> -	if (vif->task)
> -		kthread_stop(vif->task);
> +	kthread_stop(vif->task);
>  
>  	xenvif_unmap_frontend_rings(vif);
> +
> +	vif->connected = 0;
>  }
>  
>  void xenvif_free(struct xenvif *vif)
> -- 
> 1.7.10.4
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