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netpoll: Respect NETIF_F_LLTX

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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: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric W. Biederman 2014-03-27 15:42:20 -07:00 committed by David S. Miller
parent 080b3c19a4
commit 5efeac44cf
2 changed files with 10 additions and 5 deletions
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5
include/linux/netdevice.h
View file

@ -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); \

10
net/core/netpoll.c
View file

@ -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;