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Date: Thu, 13 Mar 2008 09:44:02 -0700
From: "Vernon Mauery" <vmauery@...il.com>
To: "Dhananjay Phadke" <dhananjay@...xen.com>
Cc: netdev@...r.kernel.org, "Jeff Garzik" <jeff@...zik.org>
Subject: Re: [PATCH 3/4] netxen: remove low level tx lock
On 3/12/08, Dhananjay Phadke <dhananjay@...xen.com> wrote:
>
> o eliminate tx lock in netxen adapter struct, instead pound on netdev
> tx lock appropriately.
> o remove old "concurrent transmit" code that unnecessarily drops and
> reacquires tx lock in hard_xmit_frame(), this is already serialized
> the netdev xmit lock.
> o reduce scope of tx lock in tx cleanup. tx cleanup operates on
> different section of the ring than transmitting cpus and is
> guarded by producer and consumer indices. This fixes a race
> caused by rx softirq preemption on realtime kernels.
>
> Signed-off-by: Dhananjay Phadke <dhananjay@...xen.com>
I have tested this patch on my netxen hardware and found that it fixes
a TX timeout hang that I was seeing previously.
Tested-by: Vernon Mauery <vernux@...ibm.com>
--Vernon
> ---
> drivers/net/netxen/netxen_nic.h | 14 +----
> drivers/net/netxen/netxen_nic_ethtool.c | 2 -
> drivers/net/netxen/netxen_nic_init.c | 89 ++++++-----------------------
> drivers/net/netxen/netxen_nic_main.c | 95 +++++++-----------------------
> 4 files changed, 43 insertions(+), 157 deletions(-)
>
> diff --git a/drivers/net/netxen/netxen_nic.h b/drivers/net/netxen/netxen_nic.h
> index 8b6546c..070421b 100644
> --- a/drivers/net/netxen/netxen_nic.h
> +++ b/drivers/net/netxen/netxen_nic.h
> @@ -85,7 +85,7 @@
> (sizeof(struct netxen_cmd_buffer) * adapter->max_tx_desc_count)
> #define RCV_BUFFSIZE \
> (sizeof(struct netxen_rx_buffer) * rcv_desc->max_rx_desc_count)
> -#define find_diff_among(a,b,range) ((a)<=(b)?((b)-(a)):((b)+(range)-(a)))
> +#define find_diff_among(a,b,range) ((a)<(b)?((b)-(a)):((b)+(range)-(a)))
>
> #define NETXEN_NETDEV_STATUS 0x1
> #define NETXEN_RCV_PRODUCER_OFFSET 0
> @@ -204,7 +204,7 @@ enum {
> ? RCV_DESC_LRO : \
> (RCV_DESC_NORMAL)))
>
> -#define MAX_CMD_DESCRIPTORS 1024
> +#define MAX_CMD_DESCRIPTORS 4096
> #define MAX_RCV_DESCRIPTORS 16384
> #define MAX_CMD_DESCRIPTORS_HOST (MAX_CMD_DESCRIPTORS / 4)
> #define MAX_RCV_DESCRIPTORS_1G (MAX_RCV_DESCRIPTORS / 4)
> @@ -824,9 +824,7 @@ struct netxen_adapter_stats {
> u64 uphcong;
> u64 upmcong;
> u64 updunno;
> - u64 skbfreed;
> u64 txdropped;
> - u64 txnullskb;
> u64 csummed;
> u64 no_rcv;
> u64 rxbytes;
> @@ -888,8 +886,6 @@ struct netxen_adapter {
> int mtu;
> int portnum;
>
> - spinlock_t tx_lock;
> - spinlock_t lock;
> struct work_struct watchdog_task;
> struct timer_list watchdog_timer;
> struct work_struct tx_timeout_task;
> @@ -898,16 +894,12 @@ struct netxen_adapter {
>
> u32 cmd_producer;
> __le32 *cmd_consumer;
> -
> u32 last_cmd_consumer;
> +
> u32 max_tx_desc_count;
> u32 max_rx_desc_count;
> u32 max_jumbo_rx_desc_count;
> u32 max_lro_rx_desc_count;
> - /* Num of instances active on cmd buffer ring */
> - u32 proc_cmd_buf_counter;
> -
> - u32 num_threads, total_threads; /*Use to keep track of xmit threads */
>
> u32 flags;
> u32 irq;
> diff --git a/drivers/net/netxen/netxen_nic_ethtool.c b/drivers/net/netxen/netxen_nic_ethtool.c
> index 7a876f4..d324ea3 100644
> --- a/drivers/net/netxen/netxen_nic_ethtool.c
> +++ b/drivers/net/netxen/netxen_nic_ethtool.c
> @@ -70,9 +70,7 @@ static const struct netxen_nic_stats netxen_nic_gstrings_stats[] = {
> {"uphcong", NETXEN_NIC_STAT(stats.uphcong)},
> {"upmcong", NETXEN_NIC_STAT(stats.upmcong)},
> {"updunno", NETXEN_NIC_STAT(stats.updunno)},
> - {"skb_freed", NETXEN_NIC_STAT(stats.skbfreed)},
> {"tx_dropped", NETXEN_NIC_STAT(stats.txdropped)},
> - {"tx_null_skb", NETXEN_NIC_STAT(stats.txnullskb)},
> {"csummed", NETXEN_NIC_STAT(stats.csummed)},
> {"no_rcv", NETXEN_NIC_STAT(stats.no_rcv)},
> {"rx_bytes", NETXEN_NIC_STAT(stats.rxbytes)},
> diff --git a/drivers/net/netxen/netxen_nic_init.c b/drivers/net/netxen/netxen_nic_init.c
> index 64fc18d..fe64618 100644
> --- a/drivers/net/netxen/netxen_nic_init.c
> +++ b/drivers/net/netxen/netxen_nic_init.c
> @@ -1197,96 +1197,50 @@ u32 netxen_process_rcv_ring(struct netxen_adapter *adapter, int ctxid, int max)
> /* Process Command status ring */
> int netxen_process_cmd_ring(struct netxen_adapter *adapter)
> {
> - u32 last_consumer;
> - u32 consumer;
> - int count1 = 0;
> - int count2 = 0;
> + u32 last_consumer, consumer;
> + int count = 0, i;
> struct netxen_cmd_buffer *buffer;
> - struct pci_dev *pdev;
> + struct pci_dev *pdev = adapter->pdev;
> + struct net_device *netdev = adapter->netdev;
> struct netxen_skb_frag *frag;
> - u32 i;
> - int done;
> + int done = 0;
>
> - spin_lock(&adapter->tx_lock);
> last_consumer = adapter->last_cmd_consumer;
> - DPRINTK(INFO, "procesing xmit complete\n");
> - /* we assume in this case that there is only one port and that is
> - * port #1...changes need to be done in firmware to indicate port
> - * number as part of the descriptor. This way we will be able to get
> - * the netdev which is associated with that device.
> - */
> -
> consumer = le32_to_cpu(*(adapter->cmd_consumer));
> - if (last_consumer == consumer) { /* Ring is empty */
> - DPRINTK(INFO, "last_consumer %d == consumer %d\n",
> - last_consumer, consumer);
> - spin_unlock(&adapter->tx_lock);
> - return 1;
> - }
> -
> - adapter->proc_cmd_buf_counter++;
> - /*
> - * Not needed - does not seem to be used anywhere.
> - * adapter->cmd_consumer = consumer;
> - */
> - spin_unlock(&adapter->tx_lock);
>
> - while ((last_consumer != consumer) && (count1 < MAX_STATUS_HANDLE)) {
> + while (last_consumer != consumer) {
> buffer = &adapter->cmd_buf_arr[last_consumer];
> - pdev = adapter->pdev;
> if (buffer->skb) {
> frag = &buffer->frag_array[0];
> pci_unmap_single(pdev, frag->dma, frag->length,
> PCI_DMA_TODEVICE);
> frag->dma = 0ULL;
> for (i = 1; i < buffer->frag_count; i++) {
> - DPRINTK(INFO, "getting fragment no %d\n", i);
> frag++; /* Get the next frag */
> pci_unmap_page(pdev, frag->dma, frag->length,
> PCI_DMA_TODEVICE);
> frag->dma = 0ULL;
> }
>
> - adapter->stats.skbfreed++;
> + adapter->stats.xmitfinished++;
> dev_kfree_skb_any(buffer->skb);
> buffer->skb = NULL;
> - } else if (adapter->proc_cmd_buf_counter == 1) {
> - adapter->stats.txnullskb++;
> - }
> - if (unlikely(netif_queue_stopped(adapter->netdev)
> - && netif_carrier_ok(adapter->netdev))
> - && ((jiffies - adapter->netdev->trans_start) >
> - adapter->netdev->watchdog_timeo)) {
> - SCHEDULE_WORK(&adapter->tx_timeout_task);
> }
>
> last_consumer = get_next_index(last_consumer,
> adapter->max_tx_desc_count);
> - count1++;
> + if (++count >= MAX_STATUS_HANDLE)
> + break;
> }
>
> - count2 = 0;
> - spin_lock(&adapter->tx_lock);
> - if ((--adapter->proc_cmd_buf_counter) == 0) {
> + if (count) {
> adapter->last_cmd_consumer = last_consumer;
> - while ((adapter->last_cmd_consumer != consumer)
> - && (count2 < MAX_STATUS_HANDLE)) {
> - buffer =
> - &adapter->cmd_buf_arr[adapter->last_cmd_consumer];
> - count2++;
> - if (buffer->skb)
> - break;
> - else
> - adapter->last_cmd_consumer =
> - get_next_index(adapter->last_cmd_consumer,
> - adapter->max_tx_desc_count);
> - }
> - }
> - if (count1 || count2) {
> - if (netif_queue_stopped(adapter->netdev)
> - && (adapter->flags & NETXEN_NETDEV_STATUS)) {
> - netif_wake_queue(adapter->netdev);
> - adapter->flags &= ~NETXEN_NETDEV_STATUS;
> + smp_mb();
> + if (netif_queue_stopped(netdev) && netif_running(netdev)) {
> + netif_tx_lock(netdev);
> + netif_wake_queue(netdev);
> + smp_mb();
> + netif_tx_unlock(netdev);
> }
> }
> /*
> @@ -1302,16 +1256,9 @@ int netxen_process_cmd_ring(struct netxen_adapter *adapter)
> * There is still a possible race condition and the host could miss an
> * interrupt. The card has to take care of this.
> */
> - if (adapter->last_cmd_consumer == consumer &&
> - (((adapter->cmd_producer + 1) %
> - adapter->max_tx_desc_count) == adapter->last_cmd_consumer)) {
> - consumer = le32_to_cpu(*(adapter->cmd_consumer));
> - }
> - done = (adapter->last_cmd_consumer == consumer);
> + consumer = le32_to_cpu(*(adapter->cmd_consumer));
> + done = (last_consumer == consumer);
>
> - spin_unlock(&adapter->tx_lock);
> - DPRINTK(INFO, "last consumer is %d in %s\n", last_consumer,
> - __FUNCTION__);
> return (done);
> }
>
> diff --git a/drivers/net/netxen/netxen_nic_main.c b/drivers/net/netxen/netxen_nic_main.c
> index 9595520..dc4d593 100644
> --- a/drivers/net/netxen/netxen_nic_main.c
> +++ b/drivers/net/netxen/netxen_nic_main.c
> @@ -317,7 +317,6 @@ netxen_nic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>
> adapter->ahw.pdev = pdev;
> adapter->ahw.pci_func = pci_func_id;
> - spin_lock_init(&adapter->tx_lock);
>
> /* remap phys address */
> mem_base = pci_resource_start(pdev, 0); /* 0 is for BAR 0 */
> @@ -533,7 +532,6 @@ netxen_nic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> adapter->watchdog_timer.data = (unsigned long)adapter;
> INIT_WORK(&adapter->watchdog_task, netxen_watchdog_task);
> adapter->ahw.pdev = pdev;
> - adapter->proc_cmd_buf_counter = 0;
> adapter->ahw.revision_id = pdev->revision;
>
> /* make sure Window == 1 */
> @@ -952,41 +950,17 @@ static int netxen_nic_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> struct netxen_skb_frag *buffrag;
> unsigned int i;
>
> - u32 producer = 0;
> + u32 producer, consumer;
> u32 saved_producer = 0;
> struct cmd_desc_type0 *hwdesc;
> int k;
> struct netxen_cmd_buffer *pbuf = NULL;
> - static int dropped_packet = 0;
> int frag_count;
> - u32 local_producer = 0;
> - u32 max_tx_desc_count = 0;
> - u32 last_cmd_consumer = 0;
> int no_of_desc;
> + u32 num_txd = adapter->max_tx_desc_count;
>
> - adapter->stats.xmitcalled++;
> frag_count = skb_shinfo(skb)->nr_frags + 1;
>
> - if (unlikely(skb->len <= 0)) {
> - dev_kfree_skb_any(skb);
> - adapter->stats.badskblen++;
> - return NETDEV_TX_OK;
> - }
> -
> - if (frag_count > MAX_BUFFERS_PER_CMD) {
> - printk("%s: %s netxen_nic_xmit_frame: frag_count (%d) "
> - "too large, can handle only %d frags\n",
> - netxen_nic_driver_name, netdev->name,
> - frag_count, MAX_BUFFERS_PER_CMD);
> - adapter->stats.txdropped++;
> - if ((++dropped_packet & 0xff) == 0xff)
> - printk("%s: %s droppped packets = %d\n",
> - netxen_nic_driver_name, netdev->name,
> - dropped_packet);
> -
> - return NETDEV_TX_OK;
> - }
> -
> /* There 4 fragments per descriptor */
> no_of_desc = (frag_count + 3) >> 2;
> if (netdev->features & NETIF_F_TSO) {
> @@ -1001,27 +975,16 @@ static int netxen_nic_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> }
> }
>
> - spin_lock_bh(&adapter->tx_lock);
> - if (adapter->total_threads >= MAX_XMIT_PRODUCERS) {
> - goto out_requeue;
> + producer = adapter->cmd_producer;
> + smp_mb();
> + consumer = adapter->last_cmd_consumer;
> + if ((no_of_desc+2) > find_diff_among(producer, consumer, num_txd)) {
> + netif_stop_queue(netdev);
> + smp_mb();
> + return NETDEV_TX_BUSY;
> }
> - local_producer = adapter->cmd_producer;
> - k = adapter->cmd_producer;
> - max_tx_desc_count = adapter->max_tx_desc_count;
> - last_cmd_consumer = adapter->last_cmd_consumer;
> - if ((k + no_of_desc) >=
> - ((last_cmd_consumer <= k) ? last_cmd_consumer + max_tx_desc_count :
> - last_cmd_consumer)) {
> - goto out_requeue;
> - }
> - k = get_index_range(k, max_tx_desc_count, no_of_desc);
> - adapter->cmd_producer = k;
> - adapter->total_threads++;
> - adapter->num_threads++;
>
> - spin_unlock_bh(&adapter->tx_lock);
> /* Copy the descriptors into the hardware */
> - producer = local_producer;
> saved_producer = producer;
> hwdesc = &hw->cmd_desc_head[producer];
> memset(hwdesc, 0, sizeof(struct cmd_desc_type0));
> @@ -1061,8 +1024,7 @@ static int netxen_nic_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> /* move to next desc. if there is a need */
> if ((i & 0x3) == 0) {
> k = 0;
> - producer = get_next_index(producer,
> - adapter->max_tx_desc_count);
> + producer = get_next_index(producer, num_txd);
> hwdesc = &hw->cmd_desc_head[producer];
> memset(hwdesc, 0, sizeof(struct cmd_desc_type0));
> pbuf = &adapter->cmd_buf_arr[producer];
> @@ -1080,7 +1042,6 @@ static int netxen_nic_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> buffrag->dma = temp_dma;
> buffrag->length = temp_len;
>
> - DPRINTK(INFO, "for loop. i=%d k=%d\n", i, k);
> switch (k) {
> case 0:
> hwdesc->buffer1_length = cpu_to_le16(temp_len);
> @@ -1101,7 +1062,7 @@ static int netxen_nic_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> }
> frag++;
> }
> - producer = get_next_index(producer, adapter->max_tx_desc_count);
> + producer = get_next_index(producer, num_txd);
>
> /* might change opcode to TX_TCP_LSO */
> netxen_tso_check(adapter, &hw->cmd_desc_head[saved_producer], skb);
> @@ -1128,7 +1089,7 @@ static int netxen_nic_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> /* copy the first 64 bytes */
> memcpy(((void *)hwdesc) + 2,
> (void *)(skb->data), first_hdr_len);
> - producer = get_next_index(producer, max_tx_desc_count);
> + producer = get_next_index(producer, num_txd);
>
> if (more_hdr) {
> hwdesc = &hw->cmd_desc_head[producer];
> @@ -1141,35 +1102,19 @@ static int netxen_nic_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
> hwdesc,
> (hdr_len -
> first_hdr_len));
> - producer = get_next_index(producer, max_tx_desc_count);
> + producer = get_next_index(producer, num_txd);
> }
> }
>
> - spin_lock_bh(&adapter->tx_lock);
> + adapter->cmd_producer = producer;
> adapter->stats.txbytes += skb->len;
>
> - /* Code to update the adapter considering how many producer threads
> - are currently working */
> - if ((--adapter->num_threads) == 0) {
> - /* This is the last thread */
> - u32 crb_producer = adapter->cmd_producer;
> - netxen_nic_update_cmd_producer(adapter, crb_producer);
> - wmb();
> - adapter->total_threads = 0;
> - }
> + netxen_nic_update_cmd_producer(adapter, adapter->cmd_producer);
>
> - adapter->stats.xmitfinished++;
> + adapter->stats.xmitcalled++;
> netdev->trans_start = jiffies;
>
> - spin_unlock_bh(&adapter->tx_lock);
> return NETDEV_TX_OK;
> -
> -out_requeue:
> - netif_stop_queue(netdev);
> - adapter->flags |= NETXEN_NETDEV_STATUS;
> -
> - spin_unlock_bh(&adapter->tx_lock);
> - return NETDEV_TX_BUSY;
> }
>
> static void netxen_watchdog(unsigned long v)
> @@ -1194,9 +1139,13 @@ static void netxen_tx_timeout_task(struct work_struct *work)
> printk(KERN_ERR "%s %s: transmit timeout, resetting.\n",
> netxen_nic_driver_name, adapter->netdev->name);
>
> - netxen_nic_close(adapter->netdev);
> - netxen_nic_open(adapter->netdev);
> + netxen_nic_disable_int(adapter);
> + napi_disable(&adapter->napi);
> +
> adapter->netdev->trans_start = jiffies;
> +
> + napi_enable(&adapter->napi);
> + netxen_nic_enable_int(adapter);
> netif_wake_queue(adapter->netdev);
> }
>
>
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