net: watchdog: add net device refcount tracker

Add a netdevice_tracker inside struct net_device, to track
the self reference when a device has an active watchdog timer.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netdevice.h

@@ -1951,6 +1951,7 @@ enum netdev_ml_priv_type {
  *
  *	@dev_addr_shadow:	Copy of @dev_addr to catch direct writes.
  *	@linkwatch_dev_tracker:	refcount tracker used by linkwatch.
+ *	@watchdog_dev_tracker:	refcount tracker used by watchdog.
  *
  *	FIXME: cleanup struct net_device such that network protocol info
  *	moves out.
@@ -2282,6 +2283,7 @@ struct net_device {
 
 	u8 dev_addr_shadow[MAX_ADDR_LEN];
 	netdevice_tracker	linkwatch_dev_tracker;
+	netdevice_tracker	watchdog_dev_tracker;
 };
 #define to_net_dev(d) container_of(d, struct net_device, dev)
 

net/sched/sch_generic.c

@@ -499,6 +499,7 @@ EXPORT_SYMBOL(netif_tx_unlock);
 static void dev_watchdog(struct timer_list *t)
 {
 	struct net_device *dev = from_timer(dev, t, watchdog_timer);
+	bool release = true;
 
 	spin_lock(&dev->tx_global_lock);
 	if (!qdisc_tx_is_noop(dev)) {
@@ -534,12 +535,13 @@ static void dev_watchdog(struct timer_list *t)
 			if (!mod_timer(&dev->watchdog_timer,
 				       round_jiffies(jiffies +
 						     dev->watchdog_timeo)))
-				dev_hold(dev);
+				release = false;
 		}
 	}
 	spin_unlock(&dev->tx_global_lock);
 
-	dev_put(dev);
+	if (release)
+		dev_put_track(dev, &dev->watchdog_dev_tracker);
 }
 
 void __netdev_watchdog_up(struct net_device *dev)
@@ -549,7 +551,7 @@ void __netdev_watchdog_up(struct net_device *dev)
 			dev->watchdog_timeo = 5*HZ;
 		if (!mod_timer(&dev->watchdog_timer,
 			       round_jiffies(jiffies + dev->watchdog_timeo)))
-			dev_hold(dev);
+			dev_hold_track(dev, &dev->watchdog_dev_tracker, GFP_ATOMIC);
 	}
 }
 EXPORT_SYMBOL_GPL(__netdev_watchdog_up);
@@ -563,7 +565,7 @@ static void dev_watchdog_down(struct net_device *dev)
 {
 	netif_tx_lock_bh(dev);
 	if (del_timer(&dev->watchdog_timer))
-		dev_put(dev);
+		dev_put_track(dev, &dev->watchdog_dev_tracker);
 	netif_tx_unlock_bh(dev);
 }