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Commit 5efeac44 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by David S. Miller
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netpoll: Respect NETIF_F_LLTX 



Stop taking the transmit lock when a network device has specified
NETIF_F_LLTX.

If no locks needed to trasnmit a packet this is the ideal scenario for
netpoll as all packets can be trasnmitted immediately.

Even if some locks are needed in ndo_start_xmit skipping any unnecessary
serialization is desirable for netpoll as it makes it more likely a
debugging packet may be trasnmitted immediately instead of being
deferred until later.

Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 080b3c19

include/linux/netdevice.h

+5 −0
Original line number Diff line number Diff line
@@ -2909,6 +2909,11 @@ static inline void netif_tx_unlock_bh(struct net_device *dev) 
	}						\

}



#define HARD_TX_TRYLOCK(dev, txq)			\

	(((dev->features & NETIF_F_LLTX) == 0) ?	\

		__netif_tx_trylock(txq) :		\

		true )



#define HARD_TX_UNLOCK(dev, txq) {			\

	if ((dev->features & NETIF_F_LLTX) == 0) {	\

		__netif_tx_unlock(txq);			\

net/core/netpoll.c

+5 −5
Original line number Diff line number Diff line
@@ -119,17 +119,17 @@ static void queue_process(struct work_struct *work) 
		txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));



		local_irq_save(flags);

		__netif_tx_lock(txq, smp_processor_id());

		HARD_TX_LOCK(dev, txq, smp_processor_id());

		if (netif_xmit_frozen_or_stopped(txq) ||

		    netpoll_start_xmit(skb, dev, txq) != NETDEV_TX_OK) {

			skb_queue_head(&npinfo->txq, skb);

			__netif_tx_unlock(txq);

			HARD_TX_UNLOCK(dev, txq);

			local_irq_restore(flags);



			schedule_delayed_work(&npinfo->tx_work, HZ/10);

			return;

		}

		__netif_tx_unlock(txq);

		HARD_TX_UNLOCK(dev, txq);

		local_irq_restore(flags);

	}

}
@@ -345,11 +345,11 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb, 
		/* try until next clock tick */

		for (tries = jiffies_to_usecs(1)/USEC_PER_POLL;

		     tries > 0; --tries) {

			if (__netif_tx_trylock(txq)) {

			if (HARD_TX_TRYLOCK(dev, txq)) {

				if (!netif_xmit_stopped(txq))

					status = netpoll_start_xmit(skb, dev, txq);



				__netif_tx_unlock(txq);

				HARD_TX_UNLOCK(dev, txq);



				if (status == NETDEV_TX_OK)

					break;