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Date: Tue, 12 Jan 2010 13:42:38 -0500
From: Michael Breuer <mbreuer@...jas.com>
To: Stephen Hemminger <shemminger@...tta.com>
Cc: David Miller <davem@...emloft.net>, jarkao2@...il.com,
mikem@...g3k.org, flyboy@...il.com, rjw@...k.pl,
netdev@...r.kernel.org
Subject: Re: [PATCH] sky2: safer transmit ring cleaning
On 1/12/2010 1:35 PM, Michael Breuer wrote:
> On 1/12/2010 11:15 AM, Stephen Hemminger wrote:
>> 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<shemminger@...tta.com>
>>
>> ---
>> 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.
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