[TG3]: Fix irq_sync race condition.

Gagan Arneja <gaagaan@gmail.com> pointed out that tg3_reset_task()
could potentially race with another thread calling tg3_full_lock()
such as the ethtool_set_xxx() functions.  This may trigger the
BUG_ON() in tg3_irq_quiesce() or cause the irq_sync flag to be out-
of-sync.

I think the easiest way to fix this is to get the tp->lock first
before setting the irq_sync flag.  This is safe to do because the
tp->lock is never grabbed by the irq handler.  This change will
guarantee that the irq_sync flag updates will be serialized.  We also
have to change one spot to call tg3_netif_start() (which clears the
irq_sync flag) before releasing the tp->lock.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tg3.c

@@ -3512,9 +3512,9 @@ static inline int tg3_irq_sync(struct tg3 *tp)
  */
 static inline void tg3_full_lock(struct tg3 *tp, int irq_sync)
 {
+	spin_lock_bh(&tp->lock);
 	if (irq_sync)
 		tg3_irq_quiesce(tp);
-	spin_lock_bh(&tp->lock);
 }
 
 static inline void tg3_full_unlock(struct tg3 *tp)
@@ -9116,10 +9116,10 @@ static void tg3_vlan_rx_register(struct net_device *dev, struct vlan_group *grp)
 	/* Update RX_MODE_KEEP_VLAN_TAG bit in RX_MODE register. */
 	__tg3_set_rx_mode(dev);
 
-	tg3_full_unlock(tp);
-
 	if (netif_running(dev))
 		tg3_netif_start(tp);
+
+	tg3_full_unlock(tp);
 }
 #endif