[ 70/82] r8169: fix unsigned int wraparound with TSO

Ben Hutchings
2012-06-08T05:14:13Z

From: Julien Ducourthial <jducourt@free.fr>

[ Upstream commit 477206a018f902895bfcd069dd820bfe94c187b1 ]

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.

Tested with 8111d(onboard) on a D510MO, and with 8111e(onboard) on a
Zotac 890GXITX.

Signed-off-by: Julien Ducourthial <jducourt@free.fr>
Acked-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/net/ethernet/realtek/r8169.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 5f3fa32..cc2565c 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -62,8 +62,12 @@
#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. */
@@ -5512,7 +5516,7 @@ 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;
}
@@ -5560,7 +5564,7 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,

RTL_W8(TxPoll, NPQ);

- 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.
*/
@@ -5574,7 +5578,7 @@ 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);
}

@@ -5683,7 +5687,7 @@ static void rtl8169_tx_interrupt(struct net_device *dev,
*/
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);
}
/*