Cset exclude: davem@nuts.davemloft.net|ChangeSet|20050120063740|10274

Documentation/networking/netdevices.txt

@@ -45,9 +45,10 @@ dev->hard_start_xmit:
 	Synchronization: dev->xmit_lock spinlock.
 	When the driver sets NETIF_F_LLTX in dev->features this will be
 	called without holding xmit_lock. In this case the driver 
-	has to execute it's transmission routine in a completely lockless
-	manner.  It is recommended only for queueless devices such
-	loopback and tunnels.
+	has to lock by itself when needed. It is recommended to use a try lock
+	for this and return -1 when the spin lock fails. 
+	The locking there should also properly protect against 
+	set_multicast_list
 	Context: BHs disabled
 	Notes: netif_queue_stopped() is guaranteed false
 	Return codes: 
@@ -55,6 +56,8 @@ dev->hard_start_xmit:
 	o NETDEV_TX_BUSY Cannot transmit packet, try later 
 	  Usually a bug, means queue start/stop flow control is broken in
 	  the driver. Note: the driver must NOT put the skb in its DMA ring.
+	o NETDEV_TX_LOCKED Locking failed, please retry quickly.
+	  Only valid when NETIF_F_LLTX is set.
 
 dev->tx_timeout:
 	Synchronization: dev->xmit_lock spinlock.

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -104,10 +104,10 @@ struct ipoib_buf {
 };
 
 /*
- * Device private locking: netdev->xmit_lock protects members used
- * in TX fast path.
- * lock protects everything else.  lock nests inside of xmit_lock (ie
- * xmit_lock must be acquired first if needed).
+ * Device private locking: tx_lock protects members used in TX fast
+ * path (and we use LLTX so upper layers don't do extra locking).
+ * lock protects everything else.  lock nests inside of tx_lock (ie
+ * tx_lock must be acquired first if needed).
  */
 struct ipoib_dev_priv {
 	spinlock_t lock;
@@ -150,6 +150,7 @@ struct ipoib_dev_priv {
 
 	struct ipoib_buf *rx_ring;
 
+	spinlock_t        tx_lock;
 	struct ipoib_buf *tx_ring;
 	unsigned          tx_head;
 	unsigned          tx_tail;

drivers/infiniband/ulp/ipoib/ipoib_ib.c

@@ -247,12 +247,12 @@ static void ipoib_ib_handle_wc(struct net_device *dev,
 
 		dev_kfree_skb_any(tx_req->skb);
 
-		spin_lock_irqsave(&dev->xmit_lock, flags);
+		spin_lock_irqsave(&priv->tx_lock, flags);
 		++priv->tx_tail;
 		if (netif_queue_stopped(dev) &&
 		    priv->tx_head - priv->tx_tail <= IPOIB_TX_RING_SIZE / 2)
 			netif_wake_queue(dev);
-		spin_unlock_irqrestore(&dev->xmit_lock, flags);
+		spin_unlock_irqrestore(&priv->tx_lock, flags);
 
 		if (wc->status != IB_WC_SUCCESS &&
 		    wc->status != IB_WC_WR_FLUSH_ERR)

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -411,7 +411,7 @@ static void neigh_add_path(struct sk_buff *skb, struct net_device *dev)
 
 	/*
 	 * We can only be called from ipoib_start_xmit, so we're
-	 * inside dev->xmit_lock -- no need to save/restore flags.
+	 * inside tx_lock -- no need to save/restore flags.
 	 */
 	spin_lock(&priv->lock);
 
@@ -483,7 +483,7 @@ static void unicast_arp_send(struct sk_buff *skb, struct net_device *dev,
 
 	/*
 	 * We can only be called from ipoib_start_xmit, so we're
-	 * inside dev->xmit_lock -- no need to save/restore flags.
+	 * inside tx_lock -- no need to save/restore flags.
 	 */
 	spin_lock(&priv->lock);
 
@@ -526,11 +526,27 @@ static void unicast_arp_send(struct sk_buff *skb, struct net_device *dev,
 	spin_unlock(&priv->lock);
 }
 
-/* Called with dev->xmit_lock held and IRQs disabled.  */
 static int ipoib_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 	struct ipoib_neigh *neigh;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	if (!spin_trylock(&priv->tx_lock)) {
+		local_irq_restore(flags);
+		return NETDEV_TX_LOCKED;
+	}
+
+	/*
+	 * Check if our queue is stopped.  Since we have the LLTX bit
+	 * set, we can't rely on netif_stop_queue() preventing our
+	 * xmit function from being called with a full queue.
+	 */
+	if (unlikely(netif_queue_stopped(dev))) {
+		spin_unlock_irqrestore(&priv->tx_lock, flags);
+		return NETDEV_TX_BUSY;
+	}
 
 	if (skb->dst && skb->dst->neighbour) {
 		if (unlikely(!*to_ipoib_neigh(skb->dst->neighbour))) {
@@ -585,6 +601,7 @@ static int ipoib_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 out:
+	spin_unlock_irqrestore(&priv->tx_lock, flags);
 
 	return NETDEV_TX_OK;
 }
@@ -780,7 +797,7 @@ static void ipoib_setup(struct net_device *dev)
 	dev->addr_len 		 = INFINIBAND_ALEN;
 	dev->type 		 = ARPHRD_INFINIBAND;
 	dev->tx_queue_len 	 = IPOIB_TX_RING_SIZE * 2;
-	dev->features            = NETIF_F_VLAN_CHALLENGED;
+	dev->features            = NETIF_F_VLAN_CHALLENGED | NETIF_F_LLTX;
 
 	/* MTU will be reset when mcast join happens */
 	dev->mtu 		 = IPOIB_PACKET_SIZE - IPOIB_ENCAP_LEN;
@@ -795,6 +812,7 @@ static void ipoib_setup(struct net_device *dev)
 	priv->dev = dev;
 
 	spin_lock_init(&priv->lock);
+	spin_lock_init(&priv->tx_lock);
 
 	init_MUTEX(&priv->mcast_mutex);
 	init_MUTEX(&priv->vlan_mutex);

drivers/net/e1000/e1000.h

@@ -209,6 +209,7 @@ struct e1000_adapter {
 
 	/* TX */
 	struct e1000_desc_ring tx_ring;
+	spinlock_t tx_lock;
 	uint32_t txd_cmd;
 	uint32_t tx_int_delay;
 	uint32_t tx_abs_int_delay;

drivers/net/e1000/e1000_main.c

@@ -291,9 +291,7 @@ e1000_up(struct e1000_adapter *adapter)
 			e1000_phy_reset(&adapter->hw);
 	}
 
-	spin_lock_irq(&netdev->xmit_lock);
 	e1000_set_multi(netdev);
-	spin_unlock_irq(&netdev->xmit_lock);
 
 	e1000_restore_vlan(adapter);
 
@@ -522,6 +520,9 @@ e1000_probe(struct pci_dev *pdev,
 	if(pci_using_dac)
 		netdev->features |= NETIF_F_HIGHDMA;
 
+ 	/* hard_start_xmit is safe against parallel locking */
+ 	netdev->features |= NETIF_F_LLTX; 
+ 
 	/* before reading the EEPROM, reset the controller to 
 	 * put the device in a known good starting state */
 	
@@ -731,6 +732,7 @@ e1000_sw_init(struct e1000_adapter *adapter)
 
 	atomic_set(&adapter->irq_sem, 1);
 	spin_lock_init(&adapter->stats_lock);
+	spin_lock_init(&adapter->tx_lock);
 
 	return 0;
 }
@@ -1291,8 +1293,6 @@ e1000_set_mac(struct net_device *netdev, void *p)
  * list or the network interface flags are updated.  This routine is
  * responsible for configuring the hardware for proper multicast,
  * promiscuous mode, and all-multi behavior.
- *
- * Called with netdev->xmit_lock held and IRQs disabled.
  **/
 
 static void
@@ -1304,9 +1304,12 @@ e1000_set_multi(struct net_device *netdev)
 	uint32_t rctl;
 	uint32_t hash_value;
 	int i;
+	unsigned long flags;
 
 	/* Check for Promiscuous and All Multicast modes */
 
+	spin_lock_irqsave(&adapter->tx_lock, flags);
+
 	rctl = E1000_READ_REG(hw, RCTL);
 
 	if(netdev->flags & IFF_PROMISC) {
@@ -1355,6 +1358,8 @@ e1000_set_multi(struct net_device *netdev)
 
 	if(hw->mac_type == e1000_82542_rev2_0)
 		e1000_leave_82542_rst(adapter);
+
+	spin_unlock_irqrestore(&adapter->tx_lock, flags);
 }
 
 /* Need to wait a few seconds after link up to get diagnostic information from
@@ -1781,8 +1786,6 @@ e1000_82547_fifo_workaround(struct e1000_adapter *adapter, struct sk_buff *skb)
 }
 
 #define TXD_USE_COUNT(S, X) (((S) >> (X)) + 1 )
-
-/* Called with dev->xmit_lock held and interrupts disabled.  */
 static int
 e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 {
@@ -1791,6 +1794,7 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 	unsigned int max_txd_pwr = E1000_MAX_TXD_PWR;
 	unsigned int tx_flags = 0;
 	unsigned int len = skb->len;
+	unsigned long flags;
 	unsigned int nr_frags = 0;
 	unsigned int mss = 0;
 	int count = 0;
@@ -1834,10 +1838,18 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 	if(adapter->pcix_82544)
 		count += nr_frags;
 
+ 	local_irq_save(flags); 
+ 	if (!spin_trylock(&adapter->tx_lock)) { 
+ 		/* Collision - tell upper layer to requeue */ 
+ 		local_irq_restore(flags); 
+ 		return NETDEV_TX_LOCKED; 
+ 	} 
+
 	/* need: count + 2 desc gap to keep tail from touching
 	 * head, otherwise try next time */
 	if(unlikely(E1000_DESC_UNUSED(&adapter->tx_ring) < count + 2)) {
 		netif_stop_queue(netdev);
+		spin_unlock_irqrestore(&adapter->tx_lock, flags);
 		return NETDEV_TX_BUSY;
 	}
 
@@ -1845,6 +1857,7 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 		if(unlikely(e1000_82547_fifo_workaround(adapter, skb))) {
 			netif_stop_queue(netdev);
 			mod_timer(&adapter->tx_fifo_stall_timer, jiffies);
+			spin_unlock_irqrestore(&adapter->tx_lock, flags);
 			return NETDEV_TX_BUSY;
 		}
 	}
@@ -1871,6 +1884,7 @@ e1000_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
 	if(unlikely(E1000_DESC_UNUSED(&adapter->tx_ring) < MAX_SKB_FRAGS + 2))
 		netif_stop_queue(netdev);
 
+	spin_unlock_irqrestore(&adapter->tx_lock, flags);
 	return NETDEV_TX_OK;
 }
 
@@ -2220,13 +2234,13 @@ e1000_clean_tx_irq(struct e1000_adapter *adapter)
 
 	tx_ring->next_to_clean = i;
 
-	spin_lock(&netdev->xmit_lock);
+	spin_lock(&adapter->tx_lock);
 
 	if(unlikely(cleaned && netif_queue_stopped(netdev) &&
 		    netif_carrier_ok(netdev)))
 		netif_wake_queue(netdev);
 
-	spin_unlock(&netdev->xmit_lock);
+	spin_unlock(&adapter->tx_lock);
 
 	return cleaned;
 }
@@ -2805,10 +2819,7 @@ e1000_suspend(struct pci_dev *pdev, uint32_t state)
 
 	if(wufc) {
 		e1000_setup_rctl(adapter);
-
-		spin_lock_irq(&netdev->xmit_lock);
 		e1000_set_multi(netdev);
-		spin_unlock_irq(&netdev->xmit_lock);
 
 		/* turn on all-multi mode if wake on multicast is enabled */
 		if(adapter->wol & E1000_WUFC_MC) {

drivers/net/sungem.h

@@ -953,6 +953,7 @@ enum link_state {
 
 struct gem {
 	spinlock_t lock;
+	spinlock_t tx_lock;
 	void __iomem *regs;
 	int rx_new, rx_old;
 	int tx_new, tx_old;

drivers/net/tg3.h

@@ -1980,11 +1980,12 @@ struct tg3 {
 	 * lock: Held during all operations except TX packet
 	 *       processing.
 	 *
-	 * dev->xmit_lock: Held during tg3_start_xmit and tg3_tx
+	 * tx_lock: Held during tg3_start_xmit{,_4gbug} and tg3_tx
 	 *
 	 * If you want to shut up all asynchronous processing you must
-	 * acquire both locks, 'lock' taken before 'xmit_lock'.  IRQs must
-	 * be disabled to take either lock.
+	 * acquire both locks, 'lock' taken before 'tx_lock'.  IRQs must
+	 * be disabled to take 'lock' but only softirq disabling is
+	 * necessary for acquisition of 'tx_lock'.
 	 */
 	spinlock_t			lock;
 	spinlock_t			indirect_lock;
@@ -2003,6 +2004,8 @@ struct tg3 {
 	u32				tx_cons;
 	u32				tx_pending;
 
+	spinlock_t			tx_lock;
+
 	struct tg3_tx_buffer_desc	*tx_ring;
 	struct tx_ring_info		*tx_buffers;
 	dma_addr_t			tx_desc_mapping;

include/linux/netdevice.h

@@ -76,6 +76,7 @@ struct ethtool_ops;
 /* Driver transmit return codes */
 #define NETDEV_TX_OK 0		/* driver took care of packet */
 #define NETDEV_TX_BUSY 1	/* driver tx path was busy*/
+#define NETDEV_TX_LOCKED -1	/* driver tx lock was already taken */
 
 /*
  *	Compute the worst case header length according to the protocols
@@ -414,7 +415,7 @@ struct net_device
 #define NETIF_F_HW_VLAN_FILTER	512	/* Receive filtering on VLAN */
 #define NETIF_F_VLAN_CHALLENGED	1024	/* Device cannot handle VLAN packets */
 #define NETIF_F_TSO		2048	/* Can offload TCP/IP segmentation */
-#define NETIF_F_LLTX		4096	/* Do not grab xmit_lock during ->hard_start_xmit */
+#define NETIF_F_LLTX		4096	/* LockLess TX */
 
 	/* Called after device is detached from network. */
 	void			(*uninit)(struct net_device *dev);
@@ -893,11 +894,9 @@ static inline void __netif_rx_complete(struct net_device *dev)
 
 static inline void netif_tx_disable(struct net_device *dev)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&dev->xmit_lock, flags);
+	spin_lock_bh(&dev->xmit_lock);
 	netif_stop_queue(dev);
-	spin_unlock_irqrestore(&dev->xmit_lock, flags);
+	spin_unlock_bh(&dev->xmit_lock);
 }
 
 /* These functions live elsewhere (drivers/net/net_init.c, but related) */

net/atm/clip.c

@@ -97,7 +97,7 @@ static void unlink_clip_vcc(struct clip_vcc *clip_vcc)
 		printk(KERN_CRIT "!clip_vcc->entry (clip_vcc %p)\n",clip_vcc);
 		return;
 	}
-	spin_lock_irq(&entry->neigh->dev->xmit_lock);	/* block clip_start_xmit() */
+	spin_lock_bh(&entry->neigh->dev->xmit_lock);	/* block clip_start_xmit() */
 	entry->neigh->used = jiffies;
 	for (walk = &entry->vccs; *walk; walk = &(*walk)->next)
 		if (*walk == clip_vcc) {
@@ -121,7 +121,7 @@ static void unlink_clip_vcc(struct clip_vcc *clip_vcc)
 	printk(KERN_CRIT "ATMARP: unlink_clip_vcc failed (entry %p, vcc "
 	  "0x%p)\n",entry,clip_vcc);
 out:
-	spin_unlock_irq(&entry->neigh->dev->xmit_lock);
+	spin_unlock_bh(&entry->neigh->dev->xmit_lock);
 }
 
 /* The neighbour entry n->lock is held. */

net/core/dev.c

@@ -1190,7 +1190,7 @@ int __skb_linearize(struct sk_buff *skb, int gfp_mask)
 
 #define HARD_TX_LOCK(dev, cpu) {			\
 	if ((dev->features & NETIF_F_LLTX) == 0) {	\
-		spin_lock_irq(&dev->xmit_lock);		\
+		spin_lock(&dev->xmit_lock);		\
 		dev->xmit_lock_owner = cpu;		\
 	}						\
 }
@@ -1198,7 +1198,7 @@ int __skb_linearize(struct sk_buff *skb, int gfp_mask)
 #define HARD_TX_UNLOCK(dev) {				\
 	if ((dev->features & NETIF_F_LLTX) == 0) {	\
 		dev->xmit_lock_owner = -1;		\
-		spin_unlock_irq(&dev->xmit_lock);	\
+		spin_unlock(&dev->xmit_lock);		\
 	}						\
 }
 

net/core/dev_mcast.c

@@ -93,9 +93,9 @@ static void __dev_mc_upload(struct net_device *dev)
 
 void dev_mc_upload(struct net_device *dev)
 {
-	spin_lock_irq(&dev->xmit_lock);
+	spin_lock_bh(&dev->xmit_lock);
 	__dev_mc_upload(dev);
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock_bh(&dev->xmit_lock);
 }
 
 /*
@@ -107,7 +107,7 @@ int dev_mc_delete(struct net_device *dev, void *addr, int alen, int glbl)
 	int err = 0;
 	struct dev_mc_list *dmi, **dmip;
 
-	spin_lock_irq(&dev->xmit_lock);
+	spin_lock_bh(&dev->xmit_lock);
 
 	for (dmip = &dev->mc_list; (dmi = *dmip) != NULL; dmip = &dmi->next) {
 		/*
@@ -139,13 +139,13 @@ int dev_mc_delete(struct net_device *dev, void *addr, int alen, int glbl)
 			 */
 			__dev_mc_upload(dev);
 			
-			spin_unlock_irq(&dev->xmit_lock);
+			spin_unlock_bh(&dev->xmit_lock);
 			return 0;
 		}
 	}
 	err = -ENOENT;
 done:
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock_bh(&dev->xmit_lock);
 	return err;
 }
 
@@ -160,7 +160,7 @@ int dev_mc_add(struct net_device *dev, void *addr, int alen, int glbl)
 
 	dmi1 = (struct dev_mc_list *)kmalloc(sizeof(*dmi), GFP_ATOMIC);
 
-	spin_lock_irq(&dev->xmit_lock);
+	spin_lock_bh(&dev->xmit_lock);
 	for (dmi = dev->mc_list; dmi != NULL; dmi = dmi->next) {
 		if (memcmp(dmi->dmi_addr, addr, dmi->dmi_addrlen) == 0 &&
 		    dmi->dmi_addrlen == alen) {
@@ -176,7 +176,7 @@ int dev_mc_add(struct net_device *dev, void *addr, int alen, int glbl)
 	}
 
 	if ((dmi = dmi1) == NULL) {
-		spin_unlock_irq(&dev->xmit_lock);
+		spin_unlock_bh(&dev->xmit_lock);
 		return -ENOMEM;
 	}
 	memcpy(dmi->dmi_addr, addr, alen);
@@ -189,11 +189,11 @@ int dev_mc_add(struct net_device *dev, void *addr, int alen, int glbl)
 
 	__dev_mc_upload(dev);
 	
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock_bh(&dev->xmit_lock);
 	return 0;
 
 done:
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock_bh(&dev->xmit_lock);
 	if (dmi1)
 		kfree(dmi1);
 	return err;
@@ -205,7 +205,7 @@ int dev_mc_add(struct net_device *dev, void *addr, int alen, int glbl)
 
 void dev_mc_discard(struct net_device *dev)
 {
-	spin_lock_irq(&dev->xmit_lock);
+	spin_lock_bh(&dev->xmit_lock);
 	
 	while (dev->mc_list != NULL) {
 		struct dev_mc_list *tmp = dev->mc_list;
@@ -216,7 +216,7 @@ void dev_mc_discard(struct net_device *dev)
 	}
 	dev->mc_count = 0;
 
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock_bh(&dev->xmit_lock);
 }
 
 #ifdef CONFIG_PROC_FS
@@ -251,7 +251,7 @@ static int dev_mc_seq_show(struct seq_file *seq, void *v)
 	struct dev_mc_list *m;
 	struct net_device *dev = v;
 
-	spin_lock_irq(&dev->xmit_lock);
+	spin_lock_bh(&dev->xmit_lock);
 	for (m = dev->mc_list; m; m = m->next) {
 		int i;
 
@@ -263,7 +263,7 @@ static int dev_mc_seq_show(struct seq_file *seq, void *v)
 
 		seq_putc(seq, '\n');
 	}
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock_bh(&dev->xmit_lock);
 	return 0;
 }
 

net/core/netpoll.c

@@ -188,7 +188,7 @@ static void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 		return;
 	}
 
-	spin_lock_irq(&np->dev->xmit_lock);
+	spin_lock(&np->dev->xmit_lock);
 	np->dev->xmit_lock_owner = smp_processor_id();
 
 	/*
@@ -197,7 +197,7 @@ static void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 	 */
 	if (netif_queue_stopped(np->dev)) {
 		np->dev->xmit_lock_owner = -1;
-		spin_unlock_irq(&np->dev->xmit_lock);
+		spin_unlock(&np->dev->xmit_lock);
 
 		netpoll_poll(np);
 		goto repeat;
@@ -205,7 +205,7 @@ static void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 
 	status = np->dev->hard_start_xmit(skb, np->dev);
 	np->dev->xmit_lock_owner = -1;
-	spin_unlock_irq(&np->dev->xmit_lock);
+	spin_unlock(&np->dev->xmit_lock);
 
 	/* transmit busy */
 	if(status) {

net/core/pktgen.c

@@ -2664,11 +2664,12 @@ __inline__ void pktgen_xmit(struct pktgen_dev *pkt_dev)
 		}
 	}
 	
-	spin_lock_irq(&odev->xmit_lock);
+	spin_lock_bh(&odev->xmit_lock);
 	if (!netif_queue_stopped(odev)) {
 		u64 now;
 
 		atomic_inc(&(pkt_dev->skb->users));
+retry_now:
 		ret = odev->hard_start_xmit(pkt_dev->skb, odev);
 		if (likely(ret == NETDEV_TX_OK)) {
 			pkt_dev->last_ok = 1;    
@@ -2676,6 +2677,10 @@ __inline__ void pktgen_xmit(struct pktgen_dev *pkt_dev)
 			pkt_dev->seq_num++;
 			pkt_dev->tx_bytes += pkt_dev->cur_pkt_size;
 			
+		} else if (ret == NETDEV_TX_LOCKED 
+			   && (odev->features & NETIF_F_LLTX)) {
+			cpu_relax();
+			goto retry_now;
 		} else {  /* Retry it next time */
 			
 			atomic_dec(&(pkt_dev->skb->users));
@@ -2711,7 +2716,7 @@ __inline__ void pktgen_xmit(struct pktgen_dev *pkt_dev)
 		pkt_dev->next_tx_ns = 0;
         }
 
-	spin_unlock_irq(&odev->xmit_lock);
+	spin_unlock_bh(&odev->xmit_lock);
 	
 	/* If pkt_dev->count is zero, then run forever */
 	if ((pkt_dev->count != 0) && (pkt_dev->sofar >= pkt_dev->count)) {

net/sched/sch_generic.c

@@ -99,11 +99,17 @@ int qdisc_restart(struct net_device *dev)
 	if ((skb = q->dequeue(q)) != NULL) {
 		unsigned nolock = (dev->features & NETIF_F_LLTX);
 		/*
-		 * When the driver has LLTX set it does not require any
-		 * locking in start_xmit.
+		 * When the driver has LLTX set it does its own locking
+		 * in start_xmit. No need to add additional overhead by
+		 * locking again. These checks are worth it because
+		 * even uncongested locks can be quite expensive.
+		 * The driver can do trylock like here too, in case
+		 * of lock congestion it should return -1 and the packet
+		 * will be requeued.
 		 */
 		if (!nolock) {
-			if (!spin_trylock_irq(&dev->xmit_lock)) {
+			if (!spin_trylock(&dev->xmit_lock)) {
+			collision:
 				/* So, someone grabbed the driver. */
 				
 				/* It may be transient configuration error,
@@ -137,18 +143,22 @@ int qdisc_restart(struct net_device *dev)
 				if (ret == NETDEV_TX_OK) { 
 					if (!nolock) {
 						dev->xmit_lock_owner = -1;
-						spin_unlock_irq(&dev->xmit_lock);
+						spin_unlock(&dev->xmit_lock);
 					}
 					spin_lock(&dev->queue_lock);
 					return -1;
 				}
+				if (ret == NETDEV_TX_LOCKED && nolock) {
+					spin_lock(&dev->queue_lock);
+					goto collision; 
+				}
 			}
 
 			/* NETDEV_TX_BUSY - we need to requeue */
 			/* Release the driver */
 			if (!nolock) { 
 				dev->xmit_lock_owner = -1;
-				spin_unlock_irq(&dev->xmit_lock);
+				spin_unlock(&dev->xmit_lock);
 			} 
 			spin_lock(&dev->queue_lock);
 			q = dev->qdisc;
@@ -176,7 +186,7 @@ static void dev_watchdog(unsigned long arg)
 {
 	struct net_device *dev = (struct net_device *)arg;
 
-	spin_lock_irq(&dev->xmit_lock);
+	spin_lock(&dev->xmit_lock);
 	if (dev->qdisc != &noop_qdisc) {
 		if (netif_device_present(dev) &&
 		    netif_running(dev) &&
@@ -190,7 +200,7 @@ static void dev_watchdog(unsigned long arg)
 				dev_hold(dev);
 		}
 	}
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock(&dev->xmit_lock);
 
 	dev_put(dev);
 }
@@ -214,17 +224,17 @@ void __netdev_watchdog_up(struct net_device *dev)
 
 static void dev_watchdog_up(struct net_device *dev)
 {
-	spin_lock_irq(&dev->xmit_lock);
+	spin_lock_bh(&dev->xmit_lock);
 	__netdev_watchdog_up(dev);
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock_bh(&dev->xmit_lock);
 }
 
 static void dev_watchdog_down(struct net_device *dev)
 {
-	spin_lock_irq(&dev->xmit_lock);
+	spin_lock_bh(&dev->xmit_lock);
 	if (del_timer(&dev->watchdog_timer))
 		__dev_put(dev);
-	spin_unlock_irq(&dev->xmit_lock);
+	spin_unlock_bh(&dev->xmit_lock);
 }
 
 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces

net/sched/sch_teql.c

@@ -301,12 +301,12 @@ static int teql_master_xmit(struct sk_buff *skb, struct net_device *dev)
 
 		switch (teql_resolve(skb, skb_res, slave)) {
 		case 0:
-			if (spin_trylock_irq(&slave->xmit_lock)) {
+			if (spin_trylock(&slave->xmit_lock)) {
 				slave->xmit_lock_owner = smp_processor_id();
 				if (!netif_queue_stopped(slave) &&
 				    slave->hard_start_xmit(skb, slave) == 0) {
 					slave->xmit_lock_owner = -1;
-					spin_unlock_irq(&slave->xmit_lock);
+					spin_unlock(&slave->xmit_lock);
 					master->slaves = NEXT_SLAVE(q);
 					netif_wake_queue(dev);
 					master->stats.tx_packets++;
@@ -314,7 +314,7 @@ static int teql_master_xmit(struct sk_buff *skb, struct net_device *dev)
 					return 0;
 				}
 				slave->xmit_lock_owner = -1;
-				spin_unlock_irq(&slave->xmit_lock);
+				spin_unlock(&slave->xmit_lock);
 			}
 			if (netif_queue_stopped(dev))
 				busy = 1;