DM9000: fix interface hang under load

When transferring data at full speed, the DM9000 network interface
sometimes stops sending/receiving data. Worse, ksoftirqd consumes
100% cpu and the net tx watchdog never triggers.
Fix by spin_lock_irqsave() in dm9000_start_xmit() to prevent the
interrupt handler from interfering.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 7 insertions, 18 deletions

diff --git a/drivers/net/dm9000.c b/drivers/net/dm9000.c
index c3de81bf090a..738aa5906514 100644
--- a/drivers/net/dm9000.c
+++ b/drivers/net/dm9000.c
@@ -700,6 +700,7 @@ dm9000_init_dm9000(struct net_device *dev)
 static int
 dm9000_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
+        unsigned long flags;
         board_info_t *db = (board_info_t *) dev->priv;
 
         PRINTK3("dm9000_start_xmit\n");
@@ -707,10 +708,7 @@ dm9000_start_xmit(struct sk_buff *skb, struct net_device *dev)
         if (db->tx_pkt_cnt > 1)
                 return 1;
 
-        netif_stop_queue(dev);
-
-        /* Disable all interrupts */
-        iow(db, DM9000_IMR, IMR_PAR);
+        spin_lock_irqsave(&db->lock, flags);
 
         /* Move data to DM9000 TX RAM */
         writeb(DM9000_MWCMD, db->io_addr);
@@ -718,12 +716,9 @@ dm9000_start_xmit(struct sk_buff *skb, struct net_device *dev)
         (db->outblk)(db->io_data, skb->data, skb->len);
         db->stats.tx_bytes += skb->len;
 
+        db->tx_pkt_cnt++;
         /* TX control: First packet immediately send, second packet queue */
-        if (db->tx_pkt_cnt == 0) {
-
-                /* First Packet */
-                db->tx_pkt_cnt++;
-
+        if (db->tx_pkt_cnt == 1) {
                 /* Set TX length to DM9000 */
                 iow(db, DM9000_TXPLL, skb->len & 0xff);
                 iow(db, DM9000_TXPLH, (skb->len >> 8) & 0xff);
@@ -732,23 +727,17 @@ dm9000_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 iow(db, DM9000_TCR, TCR_TXREQ); /* Cleared after TX complete */
 
                 dev->trans_start = jiffies;     /* save the time stamp */
-
         } else {
                 /* Second packet */
-                db->tx_pkt_cnt++;
                 db->queue_pkt_len = skb->len;
+                netif_stop_queue(dev);
         }
 
+        spin_unlock_irqrestore(&db->lock, flags);
+
         /* free this SKB */
         dev_kfree_skb(skb);
 
-        /* Re-enable resource check */
-        if (db->tx_pkt_cnt == 1)
-                netif_wake_queue(dev);
-
-        /* Re-enable interrupt */
-        iow(db, DM9000_IMR, IMR_PAR | IMR_PTM | IMR_PRM);
-
         return 0;
 }