netdev - Re: [PATCH net-next 3/3] r8169: use new macro netif_subqueue_completed

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Message-ID: <ac076400-e086-15be-47db-59556413094f@intel.com>
Date:   Thu, 13 Apr 2023 12:25:50 -0700
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        "Eric Dumazet" <edumazet@...gle.com>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 3/3] r8169: use new macro
 netif_subqueue_completed_wake in the tx cleanup path



On 4/13/2023 12:16 PM, Heiner Kallweit wrote:
> Use new net core macro netif_subqueue_completed_wake to simplify
> the code of the tx cleanup path.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> ---
>  drivers/net/ethernet/realtek/r8169_main.c | 16 ++++------------
>  1 file changed, 4 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> index 3f0b78fd9..5cfdb60ab 100644
> --- a/drivers/net/ethernet/realtek/r8169_main.c
> +++ b/drivers/net/ethernet/realtek/r8169_main.c
> @@ -4372,20 +4372,12 @@ static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
>  	}
>  
>  	if (tp->dirty_tx != dirty_tx) {
> -		netdev_completed_queue(dev, pkts_compl, bytes_compl);
>  		dev_sw_netstats_tx_add(dev, pkts_compl, bytes_compl);
> +		WRITE_ONCE(tp->dirty_tx, dirty_tx);
>  
> -		/* Sync with rtl8169_start_xmit:
> -		 * - publish dirty_tx ring index (write barrier)
> -		 * - refresh cur_tx ring index and queue status (read barrier)
> -		 * May the current thread miss the stopped queue condition,
> -		 * a racing xmit thread can only have a right view of the
> -		 * ring status.
> -		 */
> -		smp_store_mb(tp->dirty_tx, dirty_tx);


We used to use a smp_store_mb here, but now its safe to just WRITE_ONCE?
Assuming that's correct:

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

> -		if (netif_queue_stopped(dev) &&
> -		    rtl_tx_slots_avail(tp) >= R8169_TX_START_THRS)
> -			netif_wake_queue(dev);
> +		netif_subqueue_completed_wake(dev, 0, pkts_compl, bytes_compl,
> +					      rtl_tx_slots_avail(tp),
> +					      R8169_TX_START_THRS);
>  		/*
>  		 * 8168 hack: TxPoll requests are lost when the Tx packets are
>  		 * too close. Let's kick an extra TxPoll request when a burst