ixgbe: fix race conditions on queuing skb for HW time stamp

ixgbe has a single set of TX time stamping resources per NIC.
Use a simple bit lock to avoid race conditions and leaking skbs
when multiple TX rings try to claim time stamping.

Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c
index 8b527d7..63515a6 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c
@@ -493,6 +493,7 @@
 
 	dev_kfree_skb_any(adapter->ptp_tx_skb);
 	adapter->ptp_tx_skb = NULL;
+	clear_bit_unlock(__IXGBE_PTP_TX_IN_PROGRESS, &adapter->state);
 }
 
 /**
@@ -515,6 +516,7 @@
 	if (timeout) {
 		dev_kfree_skb_any(adapter->ptp_tx_skb);
 		adapter->ptp_tx_skb = NULL;
+		clear_bit_unlock(__IXGBE_PTP_TX_IN_PROGRESS, &adapter->state);
 		e_warn(drv, "clearing Tx Timestamp hang");
 		return;
 	}
@@ -925,6 +927,7 @@
 	if (adapter->ptp_tx_skb) {
 		dev_kfree_skb_any(adapter->ptp_tx_skb);
 		adapter->ptp_tx_skb = NULL;
+		clear_bit_unlock(__IXGBE_PTP_TX_IN_PROGRESS, &adapter->state);
 	}
 
 	if (adapter->ptp_clock) {