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r8169: improve rtl_tx 

We can simplify the for() condition and eliminate variable tx_left.
The change also considers that tp->cur_tx may be incremented by a
racing rtl8169_start_xmit().
In addition replace the write to tp->dirty_tx and the following
smp_mb() with an equivalent call to smp_store_mb(). This implicitly
adds a WRITE_ONCE() to the write.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/c2e19e5e-3d3f-d663-af32-13c3374f5def@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Heiner Kallweit 2020-11-11 22:56:29 +01:00 committed by Jakub Kicinski
parent 95f3c5458d
commit ca1ab89cd2
1 changed files with 3 additions and 4 deletions
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7
drivers/net/ethernet/realtek/r8169_main.c
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@ -4362,11 +4362,11 @@ static void rtl8169_pcierr_interrupt(struct net_device *dev)
static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
int budget)
{
unsigned int dirty_tx, tx_left, bytes_compl = 0, pkts_compl = 0;
unsigned int dirty_tx, bytes_compl = 0, pkts_compl = 0;
dirty_tx = tp->dirty_tx;
for (tx_left = READ_ONCE(tp->cur_tx) - dirty_tx; tx_left; tx_left--) {
while (READ_ONCE(tp->cur_tx) != dirty_tx) {
unsigned int entry = dirty_tx % NUM_TX_DESC;
struct sk_buff *skb = tp->tx_skb[entry].skb;
u32 status;
@ -4389,7 +4389,6 @@ static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
netdev_completed_queue(dev, pkts_compl, bytes_compl);
dev_sw_netstats_tx_add(dev, pkts_compl, bytes_compl);
tp->dirty_tx = dirty_tx;
/* Sync with rtl8169_start_xmit:
* - publish dirty_tx ring index (write barrier)
* - refresh cur_tx ring index and queue status (read barrier)
@ -4397,7 +4396,7 @@ static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp,
* a racing xmit thread can only have a right view of the
* ring status.
*/
smp_mb();
smp_store_mb(tp->dirty_tx, dirty_tx);
if (netif_queue_stopped(dev) &&
rtl_tx_slots_avail(tp, MAX_SKB_FRAGS)) {
netif_wake_queue(dev);