netxen: remove low level tx lock

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@netxen.com>
Tested-by: Vernon Mauery <mauery@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

4 files changed, 43 insertions, 157 deletions

diff --git a/drivers/net/netxen/netxen_nic.h b/drivers/net/netxen/netxen_nic.h
index 8b6546ccb47b..070421b9e4f9 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 7a876f4b8db2..d324ea3bc7ba 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 64fc18d4afb6..fe646187aa86 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 95955204ef59..dc4d593217c9 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);
 }