linux-kernel - Re: [PATCH net-next v3 2/2] net: dsa: yt921x: Protect MIB stats with a lock

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Message-ID: <20260105173342.65654f22@kernel.org>
Date: Mon, 5 Jan 2026 17:33:42 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: David Yang <mmyangfl@...il.com>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>, Vladimir Oltean
 <olteanv@...il.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 2/2] net: dsa: yt921x: Protect MIB stats
 with a lock

On Mon,  5 Jan 2026 10:09:01 +0800 David Yang wrote:
> -	pp->rx_frames = mib->rx_64byte + mib->rx_65_127byte +
> -			mib->rx_128_255byte + mib->rx_256_511byte +
> -			mib->rx_512_1023byte + mib->rx_1024_1518byte +
> -			mib->rx_jumbo;
> -	pp->tx_frames = mib->tx_64byte + mib->tx_65_127byte +
> -			mib->tx_128_255byte + mib->tx_256_511byte +
> -			mib->tx_512_1023byte + mib->tx_1024_1518byte +
> -			mib->tx_jumbo;
> -
> -	if (res)
> +	if (res) {
>  		dev_err(dev, "Failed to %s port %d: %i\n", "read stats for",
>  			port, res);
> -	return res;
> +		return res;
> +	}
> +
> +	rx_frames = mib->rx_64byte + mib->rx_65_127byte +
> +		    mib->rx_128_255byte + mib->rx_256_511byte +
> +		    mib->rx_512_1023byte + mib->rx_1024_1518byte +
> +		    mib->rx_jumbo;
> +	tx_frames = mib->tx_64byte + mib->tx_65_127byte +
> +		    mib->tx_128_255byte + mib->tx_256_511byte +
> +		    mib->tx_512_1023byte + mib->tx_1024_1518byte +
> +		    mib->tx_jumbo;

Should this not use mib_new now? (or live inside the spin lock after
copying over?)

> +	spin_lock(&pp->stats_lock);
> +	*mib = *mib_new;
> +	pp->rx_frames = rx_frames;
> +	pp->tx_frames = tx_frames;
> +	spin_unlock(&pp->stats_lock);

> diff --git a/drivers/net/dsa/yt921x.h b/drivers/net/dsa/yt921x.h
> index 61bb0ab3b09a..0c9d1b6cbc23 100644
> --- a/drivers/net/dsa/yt921x.h
> +++ b/drivers/net/dsa/yt921x.h
> @@ -533,9 +533,14 @@ struct yt921x_port {
>  	bool isolated;
>  
>  	struct delayed_work mib_read;
> +	/* protect the access to mib, rx_frames and tx_frames */
> +	spinlock_t stats_lock;

looks like spin_lock_init() is missing