netdev - Re: [Xen-devel] [PATCH net v2 1/3] xen-netback: move NAPI add/remove calls

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Date:	Mon, 11 Aug 2014 13:35:00 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Wei Liu <wei.liu2@...rix.com>, <netdev@...r.kernel.org>,
	<xen-devel@...ts.xen.org>
CC:	Ian Campbell <ian.campbell@...rix.com>,
	Zoltan Kiss <zoltan.kiss@...rix.com>
Subject: Re: [Xen-devel] [PATCH net v2 1/3] xen-netback: move NAPI add/remove
 calls

On 08/08/14 17:37, Wei Liu wrote:
> Originally napi_add was in init_queue and napi_del was in deinit_queue,
> while kthreads were handled in _connect and _disconnect. Move napi_add
> and napi_remove to _connect and _disconnect so that they reside togother
> with kthread operations.
> 
> Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> Cc: Ian Campbell <ian.campbell@...rix.com>
> Cc: Zoltan Kiss <zoltan.kiss@...rix.com>
> ---
>  drivers/net/xen-netback/interface.c |   12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index 48a55cd..fdb4fca 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -528,9 +528,6 @@ int xenvif_init_queue(struct xenvif_queue *queue)
>  
>  	init_timer(&queue->rx_stalled);
>  
> -	netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll,
> -			XENVIF_NAPI_WEIGHT);
> -
>  	return 0;
>  }
>  
> @@ -618,6 +615,9 @@ int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
>  	wake_up_process(queue->task);
>  	wake_up_process(queue->dealloc_task);
>  
> +	netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll,
> +			XENVIF_NAPI_WEIGHT);
> +
>  	return 0;
>  
>  err_rx_unbind:
> @@ -675,6 +675,11 @@ void xenvif_disconnect(struct xenvif *vif)
>  
>  	for (queue_index = 0; queue_index < num_queues; ++queue_index) {
>  		queue = &vif->queues[queue_index];
> +		netif_napi_del(&queue->napi);
> +	}

Why have you added an additional loop over all the queues?  The ordering
looks wrong as well.  I think you want

  1. unbind from irqhandler
  2. napi del
  3. stop task
  4. stop dealloc task
  5. unmap frontend rings.

David
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