bnx2x: Prevent restarting Tx during bnx2x_nic_unload

Tx queues were stopped before  bp->state was changed to a value different 
from BNX2X_STATE_OPEN, which allowed the bnx2x_tx_int() called from the 
NAPI context to re-enable it. This then allowed the netdev->ndo_start_xmit() 
to be called in the middle of the function reset and rings freeing. 

This patch changes bp->state to a value different 
from BNX2X_STATE_OPEN BEFORE disabling the Tx queues in order to restore the
broken protection against the above race in the bnx2x_tx_int().
Signed-off-by: NVladislav Zolotarov <vladz@broadcom.com>
Signed-off-by: NEilon Greenstein <eilong@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/bnx2x/bnx2x_cmn.c

@@ -1989,14 +1989,20 @@ int bnx2x_nic_unload(struct bnx2x *bp, int unload_mode)
 		return -EINVAL;
 	}
 
+	/*
+	 * It's important to set the bp->state to the value different from
+	 * BNX2X_STATE_OPEN and only then stop the Tx. Otherwise bnx2x_tx_int()
+	 * may restart the Tx from the NAPI context (see bnx2x_tx_int()).
+	 */
+	bp->state = BNX2X_STATE_CLOSING_WAIT4_HALT;
+	smp_mb();
+
 	/* Stop Tx */
 	bnx2x_tx_disable(bp);
 
 #ifdef BCM_CNIC
 	bnx2x_cnic_notify(bp, CNIC_CTL_STOP_CMD);
 #endif
-	bp->state = BNX2X_STATE_CLOSING_WAIT4_HALT;
-	smp_mb();
 
 	bp->rx_mode = BNX2X_RX_MODE_NONE;