r8169: remove unneeded memory barrier in rtl_tx

tp->dirty_tx isn't changed outside rtl_tx(). Therefore I see no need
to guarantee a specific order of reading tp->dirty_tx and tp->cur_tx.
Having said that we can remove the memory barrier.
In addition use READ_ONCE() when reading tp->cur_tx because it can
change in parallel to rtl_tx().

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/2264563a-fa9e-11b0-2c42-31bc6b8e2790@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index b6c11aa..75df476 100644 (file)
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -4364,9 +4364,8 @@ static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
        unsigned int dirty_tx, tx_left, bytes_compl = 0, pkts_compl = 0;
 
        dirty_tx = tp->dirty_tx;
-       smp_rmb();
 
-       for (tx_left = tp->cur_tx - dirty_tx; tx_left > 0; tx_left--) {
+       for (tx_left = READ_ONCE(tp->cur_tx) - dirty_tx; tx_left; tx_left--) {
                unsigned int entry = dirty_tx % NUM_TX_DESC;
                struct sk_buff *skb = tp->tx_skb[entry].skb;
                u32 status;