[TG3]: Convert to non-LLTX

Herbert Xu pointed out that it is unsafe to call netif_tx_disable()
from LLTX drivers because it uses dev->xmit_lock to synchronize
whereas LLTX drivers use private locks.

Convert tg3 to non-LLTX to fix this issue. tg3 is a lockless driver
where hard_start_xmit and tx completion handling can run concurrently
under normal conditions. A tx_lock is only needed to prevent
netif_stop_queue and netif_wake_queue race condtions when the queue
is full.

So whether we use LLTX or non-LLTX, it makes practically no
difference.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 542d4c3..b2ddd45 100644 (file)
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -3759,14 +3759,11 @@ static int tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
        len = skb_headlen(skb);
 
-       /* No BH disabling for tx_lock here.  We are running in BH disabled
-        * context and TX reclaim runs via tp->poll inside of a software
+       /* We are running in BH disabled context with netif_tx_lock
+        * and TX reclaim runs via tp->poll inside of a software
         * interrupt.  Furthermore, IRQ processing runs lockless so we have
         * no IRQ context deadlocks to worry about either.  Rejoice!
         */
-       if (!spin_trylock(&tp->tx_lock))
-               return NETDEV_TX_LOCKED;
-
        if (unlikely(TX_BUFFS_AVAIL(tp) <= (skb_shinfo(skb)->nr_frags + 1))) {
                if (!netif_queue_stopped(dev)) {
                        netif_stop_queue(dev);
@@ -3775,7 +3772,6 @@ static int tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
                        printk(KERN_ERR PFX "%s: BUG! Tx Ring full when "
                               "queue awake!\n", dev->name);
                }
-               spin_unlock(&tp->tx_lock);
                return NETDEV_TX_BUSY;
        }
 
@@ -3858,15 +3854,16 @@ static int tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
        tw32_tx_mbox((MAILBOX_SNDHOST_PROD_IDX_0 + TG3_64BIT_REG_LOW), entry);
 
        tp->tx_prod = entry;
-       if (TX_BUFFS_AVAIL(tp) <= (MAX_SKB_FRAGS + 1)) {
+       if (unlikely(TX_BUFFS_AVAIL(tp) <= (MAX_SKB_FRAGS + 1))) {
+               spin_lock(&tp->tx_lock);
                netif_stop_queue(dev);
                if (TX_BUFFS_AVAIL(tp) > TG3_TX_WAKEUP_THRESH)
                        netif_wake_queue(tp->dev);
+               spin_unlock(&tp->tx_lock);
        }
 
 out_unlock:
        mmiowb();
-       spin_unlock(&tp->tx_lock);
 
        dev->trans_start = jiffies;
 
@@ -3885,14 +3882,11 @@ static int tg3_start_xmit_dma_bug(struct sk_buff *skb, struct net_device *dev)
 
        len = skb_headlen(skb);
 
-       /* No BH disabling for tx_lock here.  We are running in BH disabled
-        * context and TX reclaim runs via tp->poll inside of a software
+       /* We are running in BH disabled context with netif_tx_lock
+        * and TX reclaim runs via tp->poll inside of a software
         * interrupt.  Furthermore, IRQ processing runs lockless so we have
         * no IRQ context deadlocks to worry about either.  Rejoice!
         */
-       if (!spin_trylock(&tp->tx_lock))
-               return NETDEV_TX_LOCKED; 
-
        if (unlikely(TX_BUFFS_AVAIL(tp) <= (skb_shinfo(skb)->nr_frags + 1))) {
                if (!netif_queue_stopped(dev)) {
                        netif_stop_queue(dev);
@@ -3901,7 +3895,6 @@ static int tg3_start_xmit_dma_bug(struct sk_buff *skb, struct net_device *dev)
                        printk(KERN_ERR PFX "%s: BUG! Tx Ring full when "
                               "queue awake!\n", dev->name);
                }
-               spin_unlock(&tp->tx_lock);
                return NETDEV_TX_BUSY;
        }
 
@@ -4039,15 +4032,16 @@ static int tg3_start_xmit_dma_bug(struct sk_buff *skb, struct net_device *dev)
        tw32_tx_mbox((MAILBOX_SNDHOST_PROD_IDX_0 + TG3_64BIT_REG_LOW), entry);
 
        tp->tx_prod = entry;
-       if (TX_BUFFS_AVAIL(tp) <= (MAX_SKB_FRAGS + 1)) {
+       if (unlikely(TX_BUFFS_AVAIL(tp) <= (MAX_SKB_FRAGS + 1))) {
+               spin_lock(&tp->tx_lock);
                netif_stop_queue(dev);
                if (TX_BUFFS_AVAIL(tp) > TG3_TX_WAKEUP_THRESH)
                        netif_wake_queue(tp->dev);
+               spin_unlock(&tp->tx_lock);
        }
 
 out_unlock:
        mmiowb();
-       spin_unlock(&tp->tx_lock);
 
        dev->trans_start = jiffies;
 
@@ -11284,7 +11278,6 @@ static int __devinit tg3_init_one(struct pci_dev *pdev,
        SET_MODULE_OWNER(dev);
        SET_NETDEV_DEV(dev, &pdev->dev);
 
-       dev->features |= NETIF_F_LLTX;
 #if TG3_VLAN_TAG_USED
        dev->features |= NETIF_F_HW_VLAN_TX | NETIF_F_HW_VLAN_RX;
        dev->vlan_rx_register = tg3_vlan_rx_register;

diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index 35669e1..8209da5 100644 (file)
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -2074,12 +2074,22 @@ struct tg3 {
 
        /* SMP locking strategy:
         *
-        * lock: Held during all operations except TX packet
-        *       processing.
+        * lock: Held during reset, PHY access, timer, and when
+        *       updating tg3_flags and tg3_flags2.
         *
-        * tx_lock: Held during tg3_start_xmit and tg3_tx
+        * tx_lock: Held during tg3_start_xmit and tg3_tx only
+        *          when calling netif_[start|stop]_queue.
+        *          tg3_start_xmit is protected by netif_tx_lock.
         *
         * Both of these locks are to be held with BH safety.
+        *
+        * Because the IRQ handler, tg3_poll, and tg3_start_xmit
+        * are running lockless, it is necessary to completely
+        * quiesce the chip with tg3_netif_stop and tg3_full_lock
+        * before reconfiguring the device.
+        *
+        * indirect_lock: Held when accessing registers indirectly
+        *                with IRQ disabling.
         */
        spinlock_t                      lock;
        spinlock_t                      indirect_lock;