net: mscc: ocelot: turn stats_lock into a spinlock

ocelot_get_stats64() currently runs unlocked and therefore may collide
with ocelot_port_update_stats() which indirectly accesses the same
counters. However, ocelot_get_stats64() runs in atomic context, and we
cannot simply take the sleepable ocelot->stats_lock mutex. We need to
convert it to an atomic spinlock first. Do that as a preparatory change.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/ocelot/felix_vsc9959.c

@@ -2171,7 +2171,7 @@ 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);
+	spin_lock(&ocelot->stats_lock);
 
 	ocelot_rmw(ocelot, SYS_STAT_CFG_STAT_VIEW(index),
 		   SYS_STAT_CFG_STAT_VIEW_M,
@@ -2188,7 +2188,7 @@ static void vsc9959_psfp_counters_get(struct ocelot *ocelot, u32 index,
 		     SYS_STAT_CFG_STAT_CLEAR_SHOT(0x10),
 		     SYS_STAT_CFG);
 
-	mutex_unlock(&ocelot->stats_lock);
+	spin_unlock(&ocelot->stats_lock);
 }
 
 static int vsc9959_psfp_filter_add(struct ocelot *ocelot, int port,

drivers/net/ethernet/mscc/ocelot.c

@@ -1906,13 +1906,13 @@ static void ocelot_check_stats_work(struct work_struct *work)
 					     stats_work);
 	int i, err;
 
-	mutex_lock(&ocelot->stats_lock);
+	spin_lock(&ocelot->stats_lock);
 	for (i = 0; i < ocelot->num_phys_ports; i++) {
 		err = ocelot_port_update_stats(ocelot, i);
 		if (err)
 			break;
 	}
-	mutex_unlock(&ocelot->stats_lock);
+	spin_unlock(&ocelot->stats_lock);
 
 	if (err)
 		dev_err(ocelot->dev, "Error %d updating ethtool stats\n",  err);
@@ -1925,7 +1925,7 @@ void ocelot_get_ethtool_stats(struct ocelot *ocelot, int port, u64 *data)
 {
 	int i, err;
 
-	mutex_lock(&ocelot->stats_lock);
+	spin_lock(&ocelot->stats_lock);
 
 	/* check and update now */
 	err = ocelot_port_update_stats(ocelot, port);
@@ -1934,7 +1934,7 @@ void ocelot_get_ethtool_stats(struct ocelot *ocelot, int port, u64 *data)
 	for (i = 0; i < ocelot->num_stats; i++)
 		*data++ = ocelot->stats[port * ocelot->num_stats + i];
 
-	mutex_unlock(&ocelot->stats_lock);
+	spin_unlock(&ocelot->stats_lock);
 
 	if (err)
 		dev_err(ocelot->dev, "Error %d updating ethtool stats\n", err);
@@ -3363,7 +3363,7 @@ int ocelot_init(struct ocelot *ocelot)
 	if (!ocelot->stats)
 		return -ENOMEM;
 
-	mutex_init(&ocelot->stats_lock);
+	spin_lock_init(&ocelot->stats_lock);
 	mutex_init(&ocelot->ptp_lock);
 	mutex_init(&ocelot->mact_lock);
 	mutex_init(&ocelot->fwd_domain_lock);
@@ -3511,7 +3511,6 @@ void ocelot_deinit(struct ocelot *ocelot)
 	cancel_delayed_work(&ocelot->stats_work);
 	destroy_workqueue(ocelot->stats_queue);
 	destroy_workqueue(ocelot->owq);
-	mutex_destroy(&ocelot->stats_lock);
 }
 EXPORT_SYMBOL(ocelot_deinit);
 

include/soc/mscc/ocelot.h

@@ -752,7 +752,7 @@ struct ocelot {
 	struct ocelot_psfp_list		psfp;
 
 	/* Workqueue to check statistics for overflow with its lock */
-	struct mutex			stats_lock;
+	spinlock_t			stats_lock;
 	u64				*stats;
 	struct delayed_work		stats_work;
 	struct workqueue_struct		*stats_queue;