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: Ben Hutchings <bhutchings@solarflare.com>

diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index eff5d300aa0a5273356d05e950a1e326115e3706..8f4cbb642bf2f0c1e4ab8c31d09a59dca568dbc6 100644 (file)
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -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;
 }
 

diff --git a/drivers/net/ethernet/sfc/ethtool.c b/drivers/net/ethernet/sfc/ethtool.c
index 52c9ee4c8aa338f835778ad9074e9995ee1be415..55a25b14d304caffd6c416e7056b1b6404fcd459 100644 (file)
--- a/drivers/net/ethernet/sfc/ethtool.c
+++ b/drivers/net/ethernet/sfc/ethtool.c
@@ -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,

diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index 9353ce801752f0c22cf7b400f1b8eb373852655e..b6040141ef7950df4a2f158e8cf5ba8da8eb27f6 100644 (file)
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -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.
  */