Re: [PATCH] r8169: fix problem with TSO (TX_BUFFS_AVAIL negative value)

From: Francois Romieu
Date: Mon May 07 2012 - 19:48:52 EST


Julien Ducourthial <jducourt@xxxxxxx> :
> The r8169 may get stuck or show bad behaviour after activating TSO :
> the net_device is not stopped when it has no more TX descriptors.
> This problem comes from TX_BUFS_AVAIL which may reach -1 when all
> transmit descriptors are in use. The patch simply tries to keep positive
> values.

It seems more than good.

Alex, Thomas, can you check if Julien's patch below fixes your broken
kernels as well ?

diff --git a/drivers/net/ethernet/realtek/r8169.c
b/drivers/net/ethernet/realtek/r8169.c
index f545093..d1e3c51 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -61,8 +61,12 @@
#define R8169_MSG_DEFAULT \
(NETIF_MSG_DRV | NETIF_MSG_PROBE | NETIF_MSG_IFUP | NETIF_MSG_IFDOWN)

-#define TX_BUFFS_AVAIL(tp) \
- (tp->dirty_tx + NUM_TX_DESC - tp->cur_tx - 1)
+#define TX_SLOTS_AVAIL(tp) \
+ (tp->dirty_tx + NUM_TX_DESC - tp->cur_tx)
+
+/* A skbuff with nr_frags needs nr_frags+1 entries in the tx queue */
+#define TX_FRAGS_READY_FOR(tp,nr_frags) \
+ (TX_SLOTS_AVAIL(tp) >= (nr_frags + 1))

/* Maximum number of multicast addresses to filter (vs.
Rx-all-multicast).
The RTL chips use a 64 element hash table based on the Ethernet CRC.
*/
@@ -5115,7 +5119,7 @@ static netdev_tx_t rtl8169_start_xmit(struct
sk_buff *skb,
u32 opts[2];
int frags;

- if (unlikely(TX_BUFFS_AVAIL(tp) < skb_shinfo(skb)->nr_frags)) {
+ if (unlikely(!TX_FRAGS_READY_FOR(tp, skb_shinfo(skb)->nr_frags))) {
netif_err(tp, drv, dev, "BUG! Tx Ring full when queue awake!\n");
goto err_stop_0;
}
@@ -5169,7 +5173,7 @@ static netdev_tx_t rtl8169_start_xmit(struct
sk_buff *skb,

mmiowb();

- if (TX_BUFFS_AVAIL(tp) < MAX_SKB_FRAGS) {
+ if (!TX_FRAGS_READY_FOR(tp, MAX_SKB_FRAGS)) {
/* Avoid wrongly optimistic queue wake-up: rtl_tx thread must
* not miss a ring update when it notices a stopped queue.
*/
@@ -5183,7 +5187,7 @@ static netdev_tx_t rtl8169_start_xmit(struct
sk_buff *skb,
* can't.
*/
smp_mb();
- if (TX_BUFFS_AVAIL(tp) >= MAX_SKB_FRAGS)
+ if (TX_FRAGS_READY_FOR(tp, MAX_SKB_FRAGS))
netif_wake_queue(dev);
}

@@ -5306,7 +5310,7 @@ static void rtl_tx(struct net_device *dev, struct
rtl8169_private *tp)
*/
smp_mb();
if (netif_queue_stopped(dev) &&
- (TX_BUFFS_AVAIL(tp) >= MAX_SKB_FRAGS)) {
+ TX_FRAGS_READY_FOR(tp, MAX_SKB_FRAGS)) {
netif_wake_queue(dev);
}
/*
--
1.7.7.6
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