netdev - [PATCH net] net: dsa: felix: fix race between reading PSFP stats and port stats

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Date:   Wed, 29 Jun 2022 21:30:07 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Maxim Kochetkov <fido_max@...ox.ru>,
        Colin Foster <colin.foster@...advantage.com>
Subject: [PATCH net] net: dsa: felix: fix race between reading PSFP stats and port stats

Both PSFP stats and the port stats read by ocelot_check_stats_work() are
indirectly read through the same mechanism - write to STAT_CFG:STAT_VIEW,
read from SYS:STAT:CNT[n].

It's just that for port stats, we write STAT_VIEW with the index of the
port, and for PSFP stats, we write STAT_VIEW with the filter index.

So if we allow them to run concurrently, ocelot_check_stats_work() may
change the view from vsc9959_psfp_counters_get(), and vice versa.

Fixes: 7d4b564d6add ("net: dsa: felix: support psfp filter on vsc9959")
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
 drivers/net/dsa/ocelot/felix_vsc9959.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index dd9085ae0922..693cd6ffbace 100644
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -1956,6 +1956,8 @@ static void vsc9959_psfp_sgi_table_del(struct ocelot *ocelot,
 static void vsc9959_psfp_counters_get(struct ocelot *ocelot, u32 index,
 				      struct felix_stream_filter_counters *counters)
 {
+	mutex_lock(&ocelot->stats_lock);
+
 	ocelot_rmw(ocelot, SYS_STAT_CFG_STAT_VIEW(index),
 		   SYS_STAT_CFG_STAT_VIEW_M,
 		   SYS_STAT_CFG);
@@ -1970,6 +1972,8 @@ static void vsc9959_psfp_counters_get(struct ocelot *ocelot, u32 index,
 		     SYS_STAT_CFG_STAT_VIEW(index) |
 		     SYS_STAT_CFG_STAT_CLEAR_SHOT(0x10),
 		     SYS_STAT_CFG);
+
+	mutex_unlock(&ocelot->stats_lock);
 }
 
 static int vsc9959_psfp_filter_add(struct ocelot *ocelot, int port,
-- 
2.25.1