On Sat, Jul 26, 2008 at 02:18:46AM -0700, David Miller wrote:
...
> I think there might be an easier way, but we may have
> to modify the state bits a little.
>
> Every call into ->hard_start_xmit() is made like this:
>
> 1. lock TX queue
> 2. check TX queue stopped
> 3. call ->hard_start_xmit() if not stopped
>
> This means that we can in fact do something like:
>
> unsigned int i;
>
> for (i = 0; i < dev->num_tx_queues; i++) {
> struct netdev_queue *txq;
>
> txq = netdev_get_tx_queue(dev, i);
> spin_lock_bh(&txq->_xmit_lock);
> netif_tx_freeze_queue(txq);
> spin_unlock_bh(&txq->_xmit_lock);
> }
>
> netif_tx_freeze_queue() just sets a new bit we add.
>
> Then we go to the ->hard_start_xmit() call sites and check this new
> "frozen" bit as well as the existing "stopped" bit.
>
> When we unfreeze each queue later, we see if it is stopped, and if not
> we schedule it's qdisc for packet processing.
I guess some additional synchronization will be added yet to prevent
parallel freeze and especially unfreeze.
Jarek P.
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