r8169: make use of xmit_more

There was a previous attempt to use xmit_more, but the change had to be
reverted because under load sometimes a transmit timeout occurred [0].
Maybe this was caused by a missing memory barrier, the new attempt
keeps the memory barrier before the call to netif_stop_queue like it
is used by the driver as of today. The new attempt also changes the
order of some calls as suggested by Eric.

[0] https://lkml.org/lkml/2019/2/10/39

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index 61a23aee0eef8955962344a7dcbd5e8d3045ea3c..109779e449cdc61c655119768b06ba0acd9dad05 100644 (file)
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -5641,6 +5641,8 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
        struct device *d = tp_to_dev(tp);
        dma_addr_t mapping;
        u32 opts[2], len;
+       bool stop_queue;
+       bool door_bell;
        int frags;
 
        if (unlikely(!rtl_tx_slots_avail(tp, skb_shinfo(skb)->nr_frags))) {
@@ -5684,13 +5686,13 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
 
        txd->opts2 = cpu_to_le32(opts[1]);
 
-       netdev_sent_queue(dev, skb->len);
-
        skb_tx_timestamp(skb);
 
        /* Force memory writes to complete before releasing descriptor */
        dma_wmb();
 
+       door_bell = __netdev_sent_queue(dev, skb->len, netdev_xmit_more());
+
        txd->opts1 = rtl8169_get_txd_opts1(opts[0], len, entry);
 
        /* Force all memory writes to complete before notifying device */
@@ -5698,14 +5700,19 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
 
        tp->cur_tx += frags + 1;
 
-       RTL_W8(tp, TxPoll, NPQ);
-
-       if (!rtl_tx_slots_avail(tp, MAX_SKB_FRAGS)) {
+       stop_queue = !rtl_tx_slots_avail(tp, MAX_SKB_FRAGS);
+       if (unlikely(stop_queue)) {
                /* Avoid wrongly optimistic queue wake-up: rtl_tx thread must
                 * not miss a ring update when it notices a stopped queue.
                 */
                smp_wmb();
                netif_stop_queue(dev);
+       }
+
+       if (door_bell)
+               RTL_W8(tp, TxPoll, NPQ);
+
+       if (unlikely(stop_queue)) {
                /* Sync with rtl_tx:
                 * - publish queue status and cur_tx ring index (write barrier)
                 * - refresh dirty_tx ring index (read barrier).