ixgbe: Do no clear Tx status bits since eop_desc provides enough info

There isn't any need to clear the status bits in the descriptors due to the
fact that the eop_desc provides enough information for us to know
that we have cleaned to the last packet that the software has put on the
ring.  The status bits are cleared as a part of putting the frame on the
ring so as long as we do not read the descriptor bit prior to reading the
value eop_desc we should be able to guarantee that we will not clean beyond
the end of the current data stream.

(cherry picked from commit 7f83a9e6292b49d1540f82f295ac8710ba562c5f)
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Joe Jin <joe.jin@oracle.com>

diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c
index f46e4124407657b422dc6faa5e3b5ea1a3d1f806..2cd7186760765f3a2b7ec3c0b8323d408adfc713 100644 (file)
--- a/drivers/net/ixgbe/ixgbe_main.c
+++ b/drivers/net/ixgbe/ixgbe_main.c
@@ -760,6 +760,9 @@ static bool ixgbe_clean_tx_irq(struct ixgbe_q_vector *q_vector,
                if (!eop_desc)
                        break;
 
+               /* prevent any other reads prior to eop_desc */
+               rmb();
+
                /* if DD is not set pending work has not been completed */
                if (!(eop_desc->wb.status & cpu_to_le32(IXGBE_TXD_STAT_DD)))
                        break;
@@ -770,12 +773,8 @@ static bool ixgbe_clean_tx_irq(struct ixgbe_q_vector *q_vector,
                /* clear next_to_watch to prevent false hangs */
                tx_buffer->next_to_watch = NULL;
 
-               /* prevent any other reads prior to eop_desc being verified */
-               rmb();
-
                do {
                        ixgbe_unmap_tx_resource(tx_ring, tx_buffer);
-                       tx_desc->wb.status = 0;
                        if (likely(tx_desc == eop_desc)) {
                                eop_desc = NULL;
                                dev_kfree_skb_any(tx_buffer->skb);