@@ -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);
+ }
}
/**
7ab87ff4c770eed71e3777936299292739fcd0fe ("via-rhine: move work from irq handler to softirq and beyond") forgot to explicitely control the lifespan of the tx_dirty and tx_cur pointers. Signed-off-by: Francois Romieu <romieu@fr.zoreil.com> --- drivers/net/ethernet/via/via-rhine.c | 51 +++++++++++++++++++++++++++++++----- 1 file changed, 45 insertions(+), 6 deletions(-)