net/cxgb4: Don't retrieve stats during recovery

We possibly retrieve the adapter's statistics during EEH recovery
and that should be disallowed. Otherwise, it would possibly incur
replicate EEH error and EEH recovery is going to fail eventually.

The patch reuses statistics lock and checks net_device is attached
before going to retrieve statistics, so that the problem can be
avoided.
Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c

@@ -4288,7 +4288,15 @@ static struct rtnl_link_stats64 *cxgb_get_stats(struct net_device *dev,
 	struct port_info *p = netdev_priv(dev);
 	struct adapter *adapter = p->adapter;
 
+	/* Block retrieving statistics during EEH error
+	 * recovery. Otherwise, the recovery might fail
+	 * and the PCI device will be removed permanently
+	 */
 	spin_lock(&adapter->stats_lock);
+	if (!netif_device_present(dev)) {
+		spin_unlock(&adapter->stats_lock);
+		return ns;
+	}
 	t4_get_port_stats(adapter, p->tx_chan, &stats);
 	spin_unlock(&adapter->stats_lock);
 
@@ -5496,12 +5504,14 @@ static pci_ers_result_t eeh_err_detected(struct pci_dev *pdev,
 	rtnl_lock();
 	adap->flags &= ~FW_OK;
 	notify_ulds(adap, CXGB4_STATE_START_RECOVERY);
+	spin_lock(&adap->stats_lock);
 	for_each_port(adap, i) {
 		struct net_device *dev = adap->port[i];
 
 		netif_device_detach(dev);
 		netif_carrier_off(dev);
 	}
+	spin_unlock(&adap->stats_lock);
 	if (adap->flags & FULL_INIT_DONE)
 		cxgb_down(adap);
 	rtnl_unlock();