8139too: fix a TX timeout watchdog thread against NAPI softirq race

Ingo's stealth lock validator detected that both thread acquire
dev->xmit_lock and tp->rx_lock in reverse order.
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>

drivers/net/8139too.c

@@ -586,6 +586,7 @@ struct rtl8139_private {
 	dma_addr_t tx_bufs_dma;
 	signed char phys[4];		/* MII device addresses. */
 	char twistie, twist_row, twist_col;	/* Twister tune state. */
+	unsigned int watchdog_fired : 1;
 	unsigned int default_port : 4;	/* Last dev->if_port value. */
 	unsigned int have_thread : 1;
 	spinlock_t lock;
@@ -638,6 +639,7 @@ static void rtl8139_set_rx_mode (struct net_device *dev);
 static void __set_rx_mode (struct net_device *dev);
 static void rtl8139_hw_start (struct net_device *dev);
 static void rtl8139_thread (void *_data);
+static void rtl8139_tx_timeout_task(void *_data);
 static struct ethtool_ops rtl8139_ethtool_ops;
 
 /* write MMIO register, with flush */
@@ -1598,13 +1600,14 @@ static void rtl8139_thread (void *_data)
 {
 	struct net_device *dev = _data;
 	struct rtl8139_private *tp = netdev_priv(dev);
-	unsigned long thr_delay;
+	unsigned long thr_delay = next_tick;
 
-	if (rtnl_shlock_nowait() == 0) {
+	if (tp->watchdog_fired) {
+		tp->watchdog_fired = 0;
+		rtl8139_tx_timeout_task(_data);
+	} else if (rtnl_shlock_nowait() == 0) {
 		rtl8139_thread_iter (dev, tp, tp->mmio_addr);
 		rtnl_unlock ();
-
-		thr_delay = next_tick;
 	} else {
 		/* unlikely race.  mitigate with fast poll. */
 		thr_delay = HZ / 2;
@@ -1631,7 +1634,8 @@ static void rtl8139_stop_thread(struct rtl8139_private *tp)
 	if (tp->have_thread) {
 		cancel_rearming_delayed_work(&tp->thread);
 		tp->have_thread = 0;
-	}
+	} else
+		flush_scheduled_work();
 }
 
 static inline void rtl8139_tx_clear (struct rtl8139_private *tp)
@@ -1642,14 +1646,13 @@ static inline void rtl8139_tx_clear (struct rtl8139_private *tp)
 	/* XXX account for unsent Tx packets in tp->stats.tx_dropped */
 }
 
-
-static void rtl8139_tx_timeout (struct net_device *dev)
+static void rtl8139_tx_timeout_task (void *_data)
 {
+	struct net_device *dev = _data;
 	struct rtl8139_private *tp = netdev_priv(dev);
 	void __iomem *ioaddr = tp->mmio_addr;
 	int i;
 	u8 tmp8;
-	unsigned long flags;
 
 	printk (KERN_DEBUG "%s: Transmit timeout, status %2.2x %4.4x %4.4x "
 		"media %2.2x.\n", dev->name, RTL_R8 (ChipCmd),
@@ -1670,23 +1673,34 @@ static void rtl8139_tx_timeout (struct net_device *dev)
 	if (tmp8 & CmdTxEnb)
 		RTL_W8 (ChipCmd, CmdRxEnb);
 
-	spin_lock(&tp->rx_lock);
+	spin_lock_bh(&tp->rx_lock);
 	/* Disable interrupts by clearing the interrupt mask. */
 	RTL_W16 (IntrMask, 0x0000);
 
 	/* Stop a shared interrupt from scavenging while we are. */
-	spin_lock_irqsave (&tp->lock, flags);
+	spin_lock_irq(&tp->lock);
 	rtl8139_tx_clear (tp);
-	spin_unlock_irqrestore (&tp->lock, flags);
+	spin_unlock_irq(&tp->lock);
 
 	/* ...and finally, reset everything */
 	if (netif_running(dev)) {
 		rtl8139_hw_start (dev);
 		netif_wake_queue (dev);
 	}
-	spin_unlock(&tp->rx_lock);
+	spin_unlock_bh(&tp->rx_lock);
 }
 
+static void rtl8139_tx_timeout (struct net_device *dev)
+{
+	struct rtl8139_private *tp = netdev_priv(dev);
+
+	if (!tp->have_thread) {
+		INIT_WORK(&tp->thread, rtl8139_tx_timeout_task, dev);
+		schedule_delayed_work(&tp->thread, next_tick);
+	} else
+		tp->watchdog_fired = 1;
+
+}
 
 static int rtl8139_start_xmit (struct sk_buff *skb, struct net_device *dev)
 {