netdev - [PATCH net 5/8] net: mscc: ocelot: fix race between ndo_get_stats64 and ocelot_check_stats

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Message-Id: <20220816135352.1431497-6-vladimir.oltean@nxp.com>
Date:   Tue, 16 Aug 2022 16:53:49 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Colin Foster <colin.foster@...advantage.com>,
        Maxim Kochetkov <fido_max@...ox.ru>
Subject: [PATCH net 5/8] net: mscc: ocelot: fix race between ndo_get_stats64 and ocelot_check_stats_work

The 2 methods can run concurrently, and one will change the window of
counters (SYS_STAT_CFG_STAT_VIEW) that the other sees. The fix is
similar to what commit 7fbf6795d127 ("net: mscc: ocelot: fix mutex lock
error during ethtool stats read") has done for ethtool -S.

Fixes: a556c76adc05 ("net: mscc: Add initial Ocelot switch support")
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 drivers/net/ethernet/mscc/ocelot_net.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/mscc/ocelot_net.c b/drivers/net/ethernet/mscc/ocelot_net.c
index 9d8cea16245e..6b9d37138844 100644
--- a/drivers/net/ethernet/mscc/ocelot_net.c
+++ b/drivers/net/ethernet/mscc/ocelot_net.c
@@ -726,6 +726,8 @@ static void ocelot_get_stats64(struct net_device *dev,
 	struct ocelot *ocelot = priv->port.ocelot;
 	int port = priv->port.index;
 
+	spin_lock(&ocelot->stats_lock);
+
 	/* Configure the port to read the stats from */
 	ocelot_write(ocelot, SYS_STAT_CFG_STAT_VIEW(port),
 		     SYS_STAT_CFG);
@@ -758,6 +760,8 @@ static void ocelot_get_stats64(struct net_device *dev,
 	stats->tx_dropped = ocelot_read(ocelot, SYS_COUNT_TX_DROPS) +
 			    ocelot_read(ocelot, SYS_COUNT_TX_AGING);
 	stats->collisions = ocelot_read(ocelot, SYS_COUNT_TX_COLLISION);
+
+	spin_unlock(&ocelot->stats_lock);
 }
 
 static int ocelot_port_fdb_add(struct ndmsg *ndm, struct nlattr *tb[],
-- 
2.34.1