linux-kernel - Re: [PATCH 1/2] net: ravb: Always process TX descriptor ring

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Date: Wed, 27 Mar 2024 23:59:53 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Paul Barker <paul.barker.ct@...renesas.com>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
CC: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>,
	<netdev@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] net: ravb: Always process TX descriptor ring

On 3/26/24 11:37 AM, Paul Barker wrote:

> The TX queue should be serviced each time the poll function is called,
> even if the full RX work budget has been consumed. This prevents
> starvation of the TX queue when RX bandwidth usage is high.
> 
> Fixes: a0d2f20650e8 ("Renesas Ethernet AVB PTP clock driver")
> Signed-off-by: Paul Barker <paul.barker.ct@...renesas.com>

[...]

> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index d1be030c8848..4f98e4e2badb 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -1324,12 +1324,12 @@ static int ravb_poll(struct napi_struct *napi, int budget)
>  	int q = napi - priv->napi;
>  	int mask = BIT(q);
>  	int quota = budget;
> +	bool rearm = true;

   I don't think we need an initializer, it gets reassigned below.
   And I'd rather call it unmask...

>  
>  	/* Processing RX Descriptor Ring */
>  	/* Clear RX interrupt */
>  	ravb_write(ndev, ~(mask | RIS0_RESERVED), RIS0);
> -	if (ravb_rx(ndev, &quota, q))
> -		goto out;
> +	rearm = !ravb_rx(ndev, &quota, q);
>  
>  	/* Processing TX Descriptor Ring */
>  	spin_lock_irqsave(&priv->lock, flags);
[...]

MBR, Sergey