linux-kernel - Re: [PATCH net-next v1 1/1] net: dsa: microchip: ksz9477: export HW stats over stats64 interface

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Message-ID: <20220217155554.bo6gcva6h2pkryou@skbuf>
Date:   Thu, 17 Feb 2022 17:55:54 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, kernel@...gutronix.de,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v1 1/1] net: dsa: microchip: ksz9477: export HW
 stats over stats64 interface

On Thu, Feb 17, 2022 at 03:07:26PM +0100, Oleksij Rempel wrote:
> +static void ksz9477_get_stats64(struct dsa_switch *ds, int port,
> +				struct rtnl_link_stats64 *stats)
> +{
> +	struct ksz_device *dev = ds->priv;
> +	struct ksz9477_stats_raw *raw;
> +	struct ksz_port_mib *mib;
> +	int ret;
> +
> +	mib = &dev->ports[port].mib;
> +	raw = (struct ksz9477_stats_raw *)mib->counters;
> +
> +	mutex_lock(&mib->cnt_mutex);

The eternal problem, ndo_get_stats64 runs in atomic context,
mutex_lock() sleeps. Please test your patches with
CONFIG_DEBUG_ATOMIC_SLEEP=y.

> +
> +	stats->rx_packets = raw->rx_bcast + raw->rx_mcast + raw->rx_ucast;
> +	stats->tx_packets = raw->tx_bcast + raw->tx_mcast + raw->tx_ucast;
> +
> +	/* HW counters are counting bytes + FCS which is not acceptable
> +	 * for rtnl_link_stats64 interface
> +	 */
> +	stats->rx_bytes = raw->rx_total - stats->rx_packets * ETH_FCS_LEN;
> +	stats->tx_bytes = raw->tx_total - stats->tx_packets * ETH_FCS_LEN;
> +
> +	stats->rx_length_errors = raw->rx_undersize + raw->rx_fragments +
> +		raw->rx_oversize;
> +
> +	stats->rx_crc_errors = raw->rx_crc_err;
> +	stats->rx_frame_errors = raw->rx_align_err;
> +	stats->rx_dropped = raw->rx_discards;
> +	stats->rx_errors = stats->rx_length_errors + stats->rx_crc_errors +
> +		stats->rx_frame_errors  + stats->rx_dropped;
> +
> +	stats->tx_window_errors = raw->tx_late_col;
> +	stats->tx_fifo_errors = raw->tx_discards;
> +	stats->tx_aborted_errors = raw->tx_exc_col;
> +	stats->tx_errors = stats->tx_window_errors + stats->tx_fifo_errors +
> +		stats->tx_aborted_errors;
> +
> +	stats->multicast = raw->rx_mcast;
> +	stats->collisions = raw->tx_total_col;
> +
> +	mutex_unlock(&mib->cnt_mutex);
> +}
> +
>  static void ksz_cfg(struct ksz_device *dev, u32 addr, u8 bits, bool set)
>  {
>  	regmap_update_bits(dev->regmap[0], addr, bits, set ? bits : 0);
> @@ -1365,6 +1447,7 @@ static const struct dsa_switch_ops ksz9477_switch_ops = {
>  	.port_mdb_del           = ksz9477_port_mdb_del,
>  	.port_mirror_add	= ksz9477_port_mirror_add,
>  	.port_mirror_del	= ksz9477_port_mirror_del,
> +	.get_stats64		= ksz9477_get_stats64,
>  };
>  
>  static u32 ksz9477_get_port_addr(int port, int offset)
> -- 
> 2.30.2
>