netdev - Re: [PATCH][net-next,v2] virtio_net: Remove u64_stats_update

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Message-ID: <20240621060504-mutt-send-email-mst@kernel.org>
Date: Fri, 21 Jun 2024 06:05:32 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Li RongQing <lirongqing@...du.com>
Cc: jasowang@...hat.com, xuanzhuo@...ux.alibaba.com, eperezma@...hat.com,
	hengqi@...ux.alibaba.com, virtualization@...ts.linux.dev,
	netdev@...r.kernel.org, kuba@...nel.org
Subject: Re: [PATCH][net-next,v2] virtio_net: Remove
 u64_stats_update_begin()/end() for stats fetch

On Fri, Jun 21, 2024 at 05:45:52PM +0800, Li RongQing wrote:
> This place is fetching the stats, u64_stats_update_begin()/end()
> should not be used, and the fetcher of stats is in the same context
> as the updater of the stats, so don't need any protection
> 
> Suggested-by: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Li RongQing <lirongqing@...du.com>


I like the added comment, makes things clearer.

Acked-by: Michael S. Tsirkin <mst@...hat.com>


> ---
>  drivers/net/virtio_net.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 61a57d1..6604339 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2336,12 +2336,12 @@ static void virtnet_rx_dim_update(struct virtnet_info *vi, struct receive_queue
>  	if (!rq->packets_in_napi)
>  		return;
>  
> -	u64_stats_update_begin(&rq->stats.syncp);
> +	/* Don't need protection when fetching stats, since fetcher and
> +	 * updater of the stats are in same context */
>  	dim_update_sample(rq->calls,
>  			  u64_stats_read(&rq->stats.packets),
>  			  u64_stats_read(&rq->stats.bytes),
>  			  &cur_sample);
> -	u64_stats_update_end(&rq->stats.syncp);
>  
>  	net_dim(&rq->dim, cur_sample);
>  	rq->packets_in_napi = 0;
> -- 
> 2.9.4