On 1/12/2010 1:35 PM, Michael Breuer wrote:

On 1/12/2010 11:15 AM, Stephen Hemminger wrote:

quoted

This code makes transmit path and transmit reset safer by:
   * adding memory barrier before checking available ring slots
   * reseting state of tx ring elements after free
   * seperate cleanup function from ring done function
   * removing mostly unused tx_next element

Signed-off-by: Stephen Hemminger<redacted>

---
Please apply this instead of the various bits and pieces flying
around labeled as sky2 panic under load

--- a/drivers/net/sky2.c    2010-01-11 10:49:50.907113126 -0800
+++ b/drivers/net/sky2.c    2010-01-11 17:36:22.027429875 -0800

@@ -1596,6 +1596,9 @@ static inline int tx_inuse(const struct
  /* Number of list elements available for next tx */
  static inline int tx_avail(const struct sky2_port *sky2)
  {
+    /* Makes sure update of tx_prod from start_xmit and
+       tx_cons from tx_done are seen. */
+    smp_mb();
      return sky2->tx_pending - tx_inuse(sky2);
  }

@@ -1618,8 +1621,7 @@ static unsigned tx_le_req(const struct s
      return count;
  }

-static void sky2_tx_unmap(struct pci_dev *pdev,
-              const struct tx_ring_info *re)
+static void sky2_tx_unmap(struct pci_dev *pdev, struct tx_ring_info 

*re)
  {
      if (re->flags&  TX_MAP_SINGLE)
          pci_unmap_single(pdev, pci_unmap_addr(re, mapaddr),

@@ -1629,6 +1631,7 @@ static void sky2_tx_unmap(struct pci_dev
          pci_unmap_page(pdev, pci_unmap_addr(re, mapaddr),
                     pci_unmap_len(re, maplen),
                     PCI_DMA_TODEVICE);
+    re->flags = 0;
  }

  /*

@@ -1804,7 +1807,8 @@ mapping_error:
  }

  /*
- * Free ring elements from starting at tx_cons until "done"
+ * Transmit complete processing
+ * Free ring elements from starting at tx_cons until done index
   *
   * NB:
   *  1. The hardware will tell us about partial completion of 

multi-part

@@ -1813,9 +1817,9 @@ mapping_error:
   *     looks at the tail of the queue of FIFO (tx_cons), not
   *     the head (tx_prod)
   */
-static void sky2_tx_complete(struct sky2_port *sky2, u16 done)
+static void sky2_tx_done(struct net_device *dev, u16 done)
  {
-    struct net_device *dev = sky2->netdev;
+    struct sky2_port *sky2 = netdev_priv(dev);
      unsigned idx;

      BUG_ON(done>= sky2->tx_ring_size);

@@ -1828,6 +1832,8 @@ static void sky2_tx_complete(struct sky2
          sky2_tx_unmap(sky2->hw->pdev, re);

          if (skb) {
+            re->skb = NULL;
+
              if (unlikely(netif_msg_tx_done(sky2)))
                  printk(KERN_DEBUG "%s: tx done %u\n",
                         dev->name, idx);

@@ -1836,13 +1842,10 @@ static void sky2_tx_complete(struct sky2
              dev->stats.tx_bytes += skb->len;

              dev_kfree_skb_any(skb);
-
-            sky2->tx_next = RING_NEXT(idx, sky2->tx_ring_size);
          }
      }

      sky2->tx_cons = idx;
-    smp_mb();

      if (tx_avail(sky2)>  MAX_SKB_TX_LE + 4)
          netif_wake_queue(dev);

@@ -1870,6 +1873,21 @@ static void sky2_tx_reset(struct sky2_hw
      sky2_write8(hw, SK_REG(port, TX_GMF_CTRL_T), GMF_RST_SET);
  }

+static void sky2_tx_clean(struct sky2_port *sky2)
+{
+    u16 idx;
+
+    for (idx = 0; idx<  sky2->tx_ring_size; idx++) {
+        struct tx_ring_info *re = sky2->tx_ring + idx;
+
+        sky2_tx_unmap(sky2->hw->pdev, re);
+        if (re->skb) {
+            dev_kfree_skb_any(re->skb);
+            re->skb = NULL;
+        }
+    }
+}
+
  /* Network shutdown */
  static int sky2_down(struct net_device *dev)
  {

@@ -1933,8 +1951,7 @@ static int sky2_down(struct net_device *
      sky2_tx_reset(hw, port);

      /* Free any pending frames stuck in HW queue */
-    sky2_tx_complete(sky2, sky2->tx_prod);
-
+    sky2_tx_clean(sky2);
      sky2_rx_clean(sky2);

      sky2_free_buffers(sky2);

@@ -2411,15 +2428,6 @@ error:
      goto resubmit;
  }

-/* Transmit complete */
-static inline void sky2_tx_done(struct net_device *dev, u16 last)
-{
-    struct sky2_port *sky2 = netdev_priv(dev);
-
-    if (netif_running(dev))
-        sky2_tx_complete(sky2, last);
-}
-
  static inline void sky2_skb_rx(const struct sky2_port *sky2,
                     u32 status, struct sk_buff *skb)
  {

@@ -4201,7 +4209,7 @@ static int sky2_debug_show(struct seq_fi

      /* Dump contents of tx ring */
      sop = 1;
-    for (idx = sky2->tx_next; idx != sky2->tx_prod&&  idx<  

sky2->tx_ring_size;
+    for (idx = sky2->tx_cons; idx != sky2->tx_prod&&  idx<  
sky2->tx_ring_size;
           idx = RING_NEXT(idx, sky2->tx_ring_size)) {
          const struct sky2_tx_le *le = sky2->tx_le + idx;
          u32 a = le32_to_cpu(le->addr);

--- a/drivers/net/sky2.h    2010-01-11 17:29:22.817088617 -0800
+++ b/drivers/net/sky2.h    2010-01-11 17:29:28.197120484 -0800

@@ -2187,7 +2187,6 @@ struct sky2_port {
      u16             tx_ring_size;
      u16             tx_cons;        /* next le to check */
      u16             tx_prod;        /* next le to use */
-    u16             tx_next;        /* debug only */

      u16             tx_pending;
      u16             tx_last_mss;

Test observations:

1. DHCP request/response sequence having some issues... can't confirm 
that it's a result of this patch, but I don't see this with the prior 
patch. Prior to this patch, if I connect a new device (Blackberry in 
this case) I see DHCPDISCOVER;DHCPOFFER;DHCPREQUEST;DHCPACK (just the 
four messages). With this patch I'm seeing repeated attempts - i.e., 
DISCOVER/OFFER 6 times before the REQUEST/ACK. This is repeatable and  
happening whether or not under load. As my original problem started 
with DHCP packets, this seems interesting. I don't see any errors 
logged (dmesg, messages, etc.).
2. Probably not related to this patch, but perhaps to the driver - 
I've finally tracked the source of my dropped RX packets. It's 
happening when a sending data to a CIFS client on a MacOS system. The 
RX drop rate seems proportional to the TX rate for SMB to that client 
- at a tx rate of about 200Kb/s I see about 20 dropped RX packets/sec 
- at 400 I see about 40.  I'm thinking therefore it's ACKs being 
dropped on RX. Why? no idea (yet). Nothing reported by ethtool or 
netstat -s remotely correlates to the number of dropped RX packets.

Let me add: the CIFS client from which the packets are dropped is 
connected via a dd-wrt router (on wifi) connected to the sky2 1G port. A 
Windows client connected directly to the 1G port does not exhibit the 
same symptoms (. I'll try later the Mac directly connected & a Wintel 
box over wifi if possible. The DD-WRT router (linksys wrt54g-tm) is 
bridged (wifi clients on same subnet as wired & serviced by DHCPD 
running on the linux box). This is also the source of the aforementioned 
perhaps-flaky DHCP connections.