Re: [PATCH v2 2/2] xen-netback: protect resource cleaning on XenBus disconnect

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Igor Druzhinin [mailto:igor.druzhinin@citrix.com]
> Sent: 17 January 2017 20:50
> To: Wei Liu <wei.liu2@citrix.com>
> Cc: Paul Durrant <Paul.Durrant@citrix.com>; xen-devel@lists.xenproject.org;
> netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Igor Druzhinin
> <igor.druzhinin@citrix.com>
> Subject: [PATCH v2 2/2] xen-netback: protect resource cleaning on XenBus
> disconnect
> 
> vif->lock is used to protect statistics gathering agents from using the
> queue structure during cleaning.
> 
> Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>

Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

> ---
>  drivers/net/xen-netback/interface.c | 6 ++++--
>  drivers/net/xen-netback/xenbus.c    | 2 ++
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-
> netback/interface.c
> index 41c69b3..c48252a 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -230,18 +230,18 @@ static struct net_device_stats
> *xenvif_get_stats(struct net_device *dev)
>  {
>  	struct xenvif *vif = netdev_priv(dev);
>  	struct xenvif_queue *queue = NULL;
> -	unsigned int num_queues = vif->num_queues;
>  	unsigned long rx_bytes = 0;
>  	unsigned long rx_packets = 0;
>  	unsigned long tx_bytes = 0;
>  	unsigned long tx_packets = 0;
>  	unsigned int index;
> 
> +	spin_lock(&vif->lock);
>  	if (vif->queues == NULL)
>  		goto out;
> 
>  	/* Aggregate tx and rx stats from each queue */
> -	for (index = 0; index < num_queues; ++index) {
> +	for (index = 0; index < vif->num_queues; ++index) {
>  		queue = &vif->queues[index];
>  		rx_bytes += queue->stats.rx_bytes;
>  		rx_packets += queue->stats.rx_packets;
> @@ -250,6 +250,8 @@ static struct net_device_stats
> *xenvif_get_stats(struct net_device *dev)
>  	}
> 
>  out:
> +	spin_unlock(&vif->lock);
> +
>  	vif->dev->stats.rx_bytes = rx_bytes;
>  	vif->dev->stats.rx_packets = rx_packets;
>  	vif->dev->stats.tx_bytes = tx_bytes;
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-
> netback/xenbus.c
> index 3e99071..d82cd71 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -503,9 +503,11 @@ static void backend_disconnect(struct backend_info
> *be)
>  		for (queue_index = 0; queue_index < be->vif-
> >num_queues; ++queue_index)
>  			xenvif_deinit_queue(&be->vif-
> >queues[queue_index]);
> 
> +		spin_lock(&be->vif->lock);
>  		vfree(be->vif->queues);
>  		be->vif->num_queues = 0;
>  		be->vif->queues = NULL;
> +		spin_unlock(&be->vif->lock);
> 
>  		xenvif_disconnect_ctrl(be->vif);
>  	}
> --
> 1.8.3.1


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