Subject: Re: [PATCH] net: remove LLTX in atl2 driver

From: Jay Cliburn <[email-masked]>
Date: Thu, 25 Sep 2008 20:24:49 -0500

On Thu, 25 Sep 2008 08:35:22 +0800
Kevin Hao <[email-masked]> wrote:

> When NETIF_F_LLTX is set, the atlx driver will use a private lock.
> But in recent kernels this implementation seems redundant and
> can cause problems where AF_PACKET sees things twice. Since
> NETIF_F_LLTX is marked as deprecated and shouldn't be used in
> new driver, this patch removes NETIF_F_LLTX and adds a mmiowb
> before sending packet.
> 
> Signed-off-by: Kevin Hao <[email-masked]>

Seems to work fine with large file (3.5 GiB) two-way scp and two-way
iperf runs.

[root@osprey ~]# ifconfig eth1
eth1      Link encap:Ethernet  HWaddr 00:13:74:00:5C:38  
          inet addr:192.168.1.33  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::213:74ff:fe00:5c38/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1492  Metric:1
          RX packets:10054352 errors:0 dropped:0 overruns:0 frame:1
          TX packets:12364268 errors:0 dropped:0 overruns:0 carrier:6
          collisions:0 txqueuelen:1000 
          RX bytes:11990462653 (11.1 GiB)  TX bytes:12351847745 (11.5 GiB)
          Memory:dbfc0000-dc000000 

Acked-by: Jay Cliburn <[email-masked]>

> ---
>  drivers/net/atlx/atl2.c |   24 +-----------------------
>  drivers/net/atlx/atl2.h |    1 -
>  2 files changed, 1 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/net/atlx/atl2.c b/drivers/net/atlx/atl2.c
> index b2995ac..3df4ee1 100644
> --- a/drivers/net/atlx/atl2.c
> +++ b/drivers/net/atlx/atl2.c
> @@ -116,7 +116,6 @@ static int __devinit atl2_sw_init(struct
> atl2_adapter *adapter) hw->max_frame_size = adapter->netdev->mtu;
>  
>  	spin_lock_init(&adapter->stats_lock);
> -	spin_lock_init(&adapter->tx_lock);
>  
>  	set_bit(__ATL2_DOWN, &adapter->flags);
>  
> @@ -749,11 +748,7 @@ static void atl2_down(struct atl2_adapter
> *adapter)
>  	 * reschedule our watchdog timer */
>  	set_bit(__ATL2_DOWN, &adapter->flags);
>  
> -#ifdef NETIF_F_LLTX
> -	netif_stop_queue(netdev);
> -#else
>  	netif_tx_disable(netdev);
> -#endif
>  
>  	/* reset MAC to disable all RX/TX */
>  	atl2_reset_hw(&adapter->hw);
> @@ -829,7 +824,6 @@ static inline int TxdFreeBytes(struct
> atl2_adapter *adapter) static int atl2_xmit_frame(struct sk_buff
> *skb, struct net_device *netdev) {
>  	struct atl2_adapter *adapter = netdev_priv(netdev);
> -	unsigned long flags;
>  	struct tx_pkt_header *txph;
>  	u32 offset, copy_len;
>  	int txs_unused;
> @@ -845,16 +839,6 @@ static int atl2_xmit_frame(struct sk_buff *skb,
> struct net_device *netdev) return NETDEV_TX_OK;
>  	}
>  
> -#ifdef NETIF_F_LLTX
> -	local_irq_save(flags);
> -	if (!spin_trylock(&adapter->tx_lock)) {
> -		/* Collision - tell upper layer to requeue */
> -		local_irq_restore(flags);
> -		return NETDEV_TX_LOCKED;
> -	}
> -#else
> -	spin_lock_irqsave(&adapter->tx_lock, flags);
> -#endif
>  	txs_unused = TxsFreeUnit(adapter);
>  	txbuf_unused = TxdFreeBytes(adapter);
>  
> @@ -862,7 +846,6 @@ static int atl2_xmit_frame(struct sk_buff *skb,
> struct net_device *netdev) txs_unused < 1) {
>  		/* not enough resources */
>  		netif_stop_queue(netdev);
> -		spin_unlock_irqrestore(&adapter->tx_lock, flags);
>  		return NETDEV_TX_BUSY;
>  	}
>  
> @@ -908,8 +891,7 @@ static int atl2_xmit_frame(struct sk_buff *skb,
> struct net_device *netdev) ATL2_WRITE_REGW(&adapter->hw,
> REG_MB_TXD_WR_IDX, (adapter->txd_write_ptr >> 2));
>  
> -	spin_unlock_irqrestore(&adapter->tx_lock, flags);
> -
> +	mmiowb();
>  	netdev->trans_start = jiffies;
>  	dev_kfree_skb_any(skb);
>  	return NETDEV_TX_OK;
> @@ -1447,10 +1429,6 @@ static int __devinit atl2_probe(struct pci_dev
> *pdev, netdev->features |= (NETIF_F_HW_VLAN_TX | NETIF_F_HW_VLAN_RX);
>  #endif
>  
> -#ifdef NETIF_F_LLTX
> -	netdev->features |= NETIF_F_LLTX;
> -#endif
> -
>  	/* Init PHY as early as possible due to power saving issue
> */ atl2_phy_init(&adapter->hw);
>  
> diff --git a/drivers/net/atlx/atl2.h b/drivers/net/atlx/atl2.h
> index 6e1f28f..09974df 100644
> --- a/drivers/net/atlx/atl2.h
> +++ b/drivers/net/atlx/atl2.h
> @@ -462,7 +462,6 @@ struct atl2_adapter {
>  	u16 link_duplex;
>  
>  	spinlock_t stats_lock;
> -	spinlock_t tx_lock;
>  
>  	struct work_struct reset_task;
>  	struct work_struct link_chg_task;