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Re: [PATCH 3/6] mac80211: ieee80211_queue_stopped returns reasons

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On Tue, Apr 9, 2013 at 2:37 AM, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote:
> On Mon, 2013-04-08 at 12:57 -0700, Thomas Pedersen wrote:
>
>> > That seems racy? Even asking whether it's stopped is racy though, what
>> > are you even trying to accomplish?
>>
>> Yeah, that's why I'd like to get the reason the first time.
>>
>> _h_mesh_fwding() checks whether the outgoing queue is stopped, to
>> avoid piling frames on the pending queue if the outgoing medium is
>> busy. I guess the idea was to avoid queueing frames faster than the
>> hardware could unload them. Maybe this doesn't actually happen, but we
>> can be a little bit smarter about when to drop forwarded frames. Like
>> if skbs are just being added to the outgoing queue, we probably
>> shouldn't.
>
> Technically I guess that can happen if your inbound link is better than
> the outbound one? But it'll depend on the AC parameters etc. too.
>
> However it seems that ieee80211_queue_stopped() is actually kinda broken
> and should only return the 'driver-stopped' reason to start with. If you
> fix that, it's probably good enough for you. I don't think in patch 4
> you should drop frames for scanning, for example.

It looks like mac80211 already just checks local->queue_stop_reasons
for being 0 (or not), so that check would still hold. I'm not 100%
sure the driver calls to ieee80211_queue_stopped() only returning true
for REASON_DRIVER are ok? What if the queues are being flushed, or say
REASON_PS is set?

-- 
Thomas
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