[PATCHv1 net] tg3: fix deadlock in tg3_change_mtu()

[David Vrabel <david.vrabel@citrix.com>]

5780 cards cannot have jumbo frames and TSO enabled together.  When
jumbo frames are enabled by setting the MTU, the TSO feature must be
cleared.  This is done indirectly by calling netdev_update_features()
which will call tg3_fix_features() to actually clear the flags.

netdev_update_features() will also trigger a new netlink message for
the feature change event which will result in a call to
tg3_get_stats64() which deadlocks on the tg3 lock.

Fix this by dropping the tg3 lock while calling
netdev_update_features().  This is safe as the device is down and the
hardware is stopped.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 drivers/net/ethernet/broadcom/tg3.c |   18 +++++++++++-------
 1 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index e2ca03e..0b344c0 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -14077,17 +14077,13 @@ static inline void tg3_set_mtu(struct net_device *dev, struct tg3 *tp,
 	dev->mtu = new_mtu;
 
 	if (new_mtu > ETH_DATA_LEN) {
-		if (tg3_flag(tp, 5780_CLASS)) {
-			netdev_update_features(dev);
+		if (tg3_flag(tp, 5780_CLASS))
 			tg3_flag_clear(tp, TSO_CAPABLE);
-		} else {
+		else
 			tg3_flag_set(tp, JUMBO_RING_ENABLE);
-		}
 	} else {
-		if (tg3_flag(tp, 5780_CLASS)) {
+		if (tg3_flag(tp, 5780_CLASS))
 			tg3_flag_set(tp, TSO_CAPABLE);
-			netdev_update_features(dev);
-		}
 		tg3_flag_clear(tp, JUMBO_RING_ENABLE);
 	}
 }
@@ -14119,6 +14115,14 @@ static int tg3_change_mtu(struct net_device *dev, int new_mtu)
 
 	tg3_set_mtu(dev, tp, new_mtu);
 
+	tg3_full_unlock(tp);
+
+	/* Adjusting MTU may add/remove TSO feature. */
+	if (tg3_flag(tp, 5780_CLASS))
+		netdev_update_features(dev);
+
+	tg3_full_lock(tp, 0);
+
 	/* Reset PHY, otherwise the read DMA engine will be in a mode that
 	 * breaks all requests to 256 bytes.
 	 */
-- 
1.7.2.5