netdev - Re: [PATCH net-next v3 17/19] net: ravb: Return cached statistics if the interface is down

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Message-ID: <af5ab82e-5904-c33b-983e-b37844dab3f5@omp.ru>
Date: Mon, 8 Jan 2024 23:22:48 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Claudiu <claudiu.beznea@...on.dev>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<richardcochran@...il.com>, <p.zabel@...gutronix.de>,
	<yoshihiro.shimoda.uh@...esas.com>, <wsa+renesas@...g-engineering.com>
CC: <netdev@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <geert+renesas@...der.be>, Claudiu Beznea
	<claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH net-next v3 17/19] net: ravb: Return cached statistics if
 the interface is down

On 1/5/24 11:23 AM, Claudiu wrote:

> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> 
> Return the cached statistics in case the interface is down. There should be
> no drawback to this, as cached statistics are updated in ravb_close().
> 
> The commit prepares the code for the addition of runtime PM support.
> 
> Suggested-by: Sergey Shtylyov <s.shtylyov@....ru>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
[...]

> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 76035afd4054..168b6208db37 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -2117,6 +2117,9 @@ static struct net_device_stats *ravb_get_stats(struct net_device *ndev)
>  	const struct ravb_hw_info *info = priv->info;
>  	struct net_device_stats *nstats, *stats0, *stats1;
>  
> +	if (!(ndev->flags & IFF_UP))

   Well, I guess it's OK to read the counters in the reset mode... BUT
won't this race with pm_runtime_put_autosuspend() when its call gets added
to ravb_close()?

> +		return &ndev->stats;
> +
>  	nstats = &ndev->stats;
>  	stats0 = &priv->stats[RAVB_BE];
>  
[...]

MBR, Sergey