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Commit 1cb34522 authored by Ben Hutchings's avatar Ben Hutchings
Browse files

sfc: Hold efx_nic::stats_lock while reading efx_nic::mac_stats 



efx_nic::stats_lock is used to serialise stats updates, but each
reader was dropping it before it finished reading efx_nic::mac_stats.

If there were concurrent stats reads using procfs, or one using procfs
and one using ethtool, an update could race with a read.  On a 32-bit
system, the reader could see word-tearing of 64-bit stats (32 bits of
the old value and 32 bits of the new).

Signed-off-by: default avatarBen Hutchings <bhutchings@solarflare.com>
parent 788ec41c

drivers/net/ethernet/sfc/efx.c

+3 −1
Original line number Diff line number Diff line
@@ -1743,8 +1743,8 @@ static struct rtnl_link_stats64 *efx_net_stats(struct net_device *net_dev, struc 
	struct efx_mac_stats *mac_stats = &efx->mac_stats;



	spin_lock_bh(&efx->stats_lock);



	efx->type->update_stats(efx);

	spin_unlock_bh(&efx->stats_lock);



	stats->rx_packets = mac_stats->rx_packets;

	stats->tx_packets = mac_stats->tx_packets;
@@ -1768,6 +1768,8 @@ static struct rtnl_link_stats64 *efx_net_stats(struct net_device *net_dev, struc 
	stats->tx_errors = (stats->tx_window_errors +

			    mac_stats->tx_bad);



	spin_unlock_bh(&efx->stats_lock);



	return stats;

}

drivers/net/ethernet/sfc/ethtool.c

+5 −2
Original line number Diff line number Diff line
@@ -489,13 +489,14 @@ static void efx_ethtool_get_stats(struct net_device *net_dev, 
	const struct efx_ethtool_stat *stat;

	struct efx_channel *channel;

	struct efx_tx_queue *tx_queue;

	struct rtnl_link_stats64 temp;

	int i;



	EFX_BUG_ON_PARANOID(stats->n_stats != EFX_ETHTOOL_NUM_STATS);



	spin_lock_bh(&efx->stats_lock);



	/* Update MAC and NIC statistics */

	dev_get_stats(net_dev, &temp);

	efx->type->update_stats(efx);



	/* Fill detailed statistics buffer */

	for (i = 0; i < EFX_ETHTOOL_NUM_STATS; i++) {
@@ -525,6 +526,8 @@ static void efx_ethtool_get_stats(struct net_device *net_dev, 
			break;

		}

	}



	spin_unlock_bh(&efx->stats_lock);

}



static void efx_ethtool_self_test(struct net_device *net_dev,

drivers/net/ethernet/sfc/net_driver.h

+1 −0
Original line number Diff line number Diff line
@@ -704,6 +704,7 @@ struct efx_filter_state; 
 *	can provide.  Generic code converts these into a standard

 *	&struct net_device_stats.

 * @stats_lock: Statistics update lock. Serialises statistics fetches

 *	and access to @mac_stats.

 *

 * This is stored in the private area of the &struct net_device.

 */