On Sun, 5 Nov 2006 18:28:33 +0100
"Eric Lemoine" <[EMAIL PROTECTED]> wrote:
> > You could also just use net_tx_lock() now.
>
> You mean netif_tx_lock()?
>
> Thanks for letting me know about that function. Yes, I may need it.
> tg3 and bnx2 use it to wake up the transmit queue:
>
> if (unlikely(netif_queue_stopped(tp->dev) &&
> (tg3_tx_avail(tp) > TG3_TX_WAKEUP_THRESH))) {
> netif_tx_lock(tp->dev);
> if (netif_queue_stopped(tp->dev) &&
> (tg3_tx_avail(tp) > TG3_TX_WAKEUP_THRESH))
> netif_wake_queue(tp->dev);
> netif_tx_unlock(tp->dev);
> }
>
> 2.6.17 didn't use it. Was it a bug?
>
> Thanks,
No, it was introduced in 2.6.18. The functions are just a wrapper
around the network device transmit lock that is normally held.
If the device does not need to acquire the lock during IRQ, it
is a good alternative and avoids a second lock.
For transmit locking there are three common alternatives:
Method A: dev->queue_xmit_lock and per-device tx_lock
send: dev->xmit_lock held by caller
dev->hard_start_xmit acquires netdev_priv(dev)->tx_lock
irq: netdev_priv(dev)->tx_lock acquired
Method B: dev->queue_xmit_lock only
send: dev->xmit_lock held by caller
irq: schedules softirq (NAPI)
napi_poll: calls netif_tx_lock() which acquires dev->xmit_lock
Method C: LLTX
set dev->features LLTX
send: no locks held by caller
dev->hard_start_xmit acquires netdev_priv(dev)->tx_lock
irq: netdev_priv(dev)->tx_lock acquired
Method A is the only one that works with 2.4 and early (2.6.8?) kernels.
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