[PATCH net 2/3] igb: skip reset in igb_tx_timeout() during XDP transition

[Alex Dvoretsky <advoretsky@gmail.com>]

When igb_xdp_setup() transitions between XDP and non-XDP mode on a
running device, it calls igb_close() followed by igb_open(). During
this window the adapter is down and trans_start is stale, so the TX
watchdog can fire a spurious timeout.

The resulting schedule_work(&adapter->reset_task) races with the
igb_open() path: the reset task may run while the device is being
brought back up, or immediately after, causing unexpected ring
reinitialisation and register writes.

Fix this by checking __IGB_DOWN at the top of igb_tx_timeout(). If the
adapter is down (either during normal close or during the XDP close/open
transition), there is nothing useful a reset can do — the subsequent
igb_open() will reinitialise everything.

Fixes: 9cbc948b5a20 ("igb: add XDP support")
Cc: stable@vger.kernel.org
Signed-off-by: Alex Dvoretsky <advoretsky@gmail.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 223a10cae4a9..ddb7ce9e97bf 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6651,6 +6651,15 @@ static void igb_tx_timeout(struct net_device *netdev, unsigned int __always_unus
 	struct igb_adapter *adapter = netdev_priv(netdev);
 	struct e1000_hw *hw = &adapter->hw;
 
+	/* Do not schedule a reset if the adapter is already going down or
+	 * being reconfigured (e.g., XDP program transition via igb_close/
+	 * igb_open). The stale trans_start from before the close will
+	 * trigger a spurious timeout that resolves once igb_open()
+	 * completes.
+	 */
+	if (test_bit(__IGB_DOWN, &adapter->state))
+		return;
+
 	/* Do the reset outside of interrupt context */
 	adapter->tx_timeout_count++;
 
-- 
2.51.0