diff options
| -rw-r--r-- | drivers/net/ethernet/via/via-rhine.c | 51 |
1 files changed, 45 insertions, 6 deletions
diff --git a/drivers/net/ethernet/via/via-rhine.c b/drivers/net/ethernet/via/via-rhine.c index 86ca8b2..725106f 100644 --- a/drivers/net/ethernet/via/via-rhine.c +++ b/drivers/net/ethernet/via/via-rhine.c @@ -1779,6 +1779,11 @@ static void rhine_tx_timeout(struct net_device *dev) schedule_work(&rp->reset_task); } +static inline bool rhine_tx_queue_full(struct rhine_private *rp) +{ + return (rp->cur_tx - rp->dirty_tx) >= TX_QUEUE_LEN; +} + static netdev_tx_t rhine_start_tx(struct sk_buff *skb, struct net_device *dev) { @@ -1854,6 +1859,12 @@ static netdev_tx_t rhine_start_tx(struct sk_buff *skb, wmb(); rp->cur_tx++; + /* + * Nobody wants cur_tx write to rot for ages after the NIC will have + * seen the transmit request, especially as the transmit completion + * handler could miss it. + */ + smp_wmb(); /* Non-x86 Todo: explicitly flush cache lines here. */ @@ -1866,8 +1877,14 @@ static netdev_tx_t rhine_start_tx(struct sk_buff *skb, ioaddr + ChipCmd1); IOSYNC; - if (rp->cur_tx == rp->dirty_tx + TX_QUEUE_LEN) + /* dirty_tx may be pessimistically out-of-sync. See rhine_tx. */ + if (rhine_tx_queue_full(rp)) { netif_stop_queue(dev); + smp_rmb(); + /* Rejuvenate. */ + if (!rhine_tx_queue_full(rp)) + netif_wake_queue(dev); + } netif_dbg(rp, tx_queued, dev, "Transmit frame #%d queued in slot %d\n", rp->cur_tx - 1, entry); @@ -1915,13 +1932,24 @@ static void rhine_tx(struct net_device *dev) { struct rhine_private *rp = netdev_priv(dev); struct device *hwdev = dev->dev.parent; - int txstatus = 0, entry = rp->dirty_tx % TX_RING_SIZE; unsigned int pkts_compl = 0, bytes_compl = 0; + unsigned int dirty_tx = rp->dirty_tx; + unsigned int cur_tx; struct sk_buff *skb; + /* + * The race with rhine_start_tx does not matter here as long as the + * driver enforces a value of cur_tx that was relevant when the + * packet was scheduled to the network chipset. + * Executive summary: smp_rmb() balances smp_wmb() in rhine_start_tx. + */ + smp_rmb(); + cur_tx = rp->cur_tx; /* find and cleanup dirty tx descriptors */ - while (rp->dirty_tx != rp->cur_tx) { - txstatus = le32_to_cpu(rp->tx_ring[entry].tx_status); + while (dirty_tx != cur_tx) { + unsigned int entry = dirty_tx % TX_RING_SIZE; + u32 txstatus = le32_to_cpu(rp->tx_ring[entry].tx_status); + netif_dbg(rp, tx_done, dev, "Tx scavenge %d status %08x\n", entry, txstatus); if (txstatus & DescOwn) @@ -1970,12 +1998,23 @@ static void rhine_tx(struct net_device *dev) pkts_compl++; dev_consume_skb_any(skb); rp->tx_skbuff[entry] = NULL; - entry = (++rp->dirty_tx) % TX_RING_SIZE; + dirty_tx++; } + rp->dirty_tx = dirty_tx; + /* Pity we can't rely on the nearby BQL completion implicit barrier. */ + smp_wmb(); + netdev_completed_queue(dev, pkts_compl, bytes_compl); - if ((rp->cur_tx - rp->dirty_tx) < TX_QUEUE_LEN - 4) + + /* cur_tx may be optimistically out-of-sync. See rhine_start_tx. */ + if (!rhine_tx_queue_full(rp) && netif_queue_stopped(dev)) { netif_wake_queue(dev); + smp_rmb(); + /* Rejuvenate. */ + if (rhine_tx_queue_full(rp)) + netif_stop_queue(dev); + } } /** |