Re: [RFC] mac80211: move TX status processing to process context

[Johannes Berg <johannes@sipsolutions.net>]

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On Wed, 2009-11-18 at 13:06 -0800, Luis R. Rodriguez wrote:

> OK, but can't you still have a driver spam mac80211 with a lot of
> ieee80211_tx_status_irqsafe() calls in soft irq context with the final
> skb requiring the tx complete, in that case the queue *will* get stuffed
> and you could potentially free more if so desired.

But it'll get stuffed one by one, and we free them as we stuff the
queue, so it can't ever loop :)

> Also, if our goal is to just avoid adding the skb if it does not require
> a tx complete and our queue size is too large
> 
> 	if (!(info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS) &&
> 	    num + 1 > IEEE80211_TX_STATUS_QUEUE_LIMIT)
> 		dev_kfree_skb_irq(skb);
> 	else
> 		skb_queue_tail(&local->skb_queue)

No, we actually want to drop the older ones in that case.

> > However ... right now we never use _any_ unreliable at all, but I
> > suspect we will want to change that again at some point.
> 
> Just curious -- what would be a use case for that?

Any time we don't need TX status for rate control it'd be OK to drop
frames that we don't need the status for. For example the hw-rc case my
patch from yesterday introduced.

johannes

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