netdev - Re: iwlwifi warnings in 5.5-rc1

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Date:   Wed, 11 Dec 2019 11:23:02 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Johannes Berg <johannes@...solutions.net>,
        Jens Axboe <axboe@...nel.dk>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>
Cc:     "linux-wireless\@vger.kernel.org" <linux-wireless@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: iwlwifi warnings in 5.5-rc1

Johannes Berg <johannes@...solutions.net> writes:

> On Wed, 2019-12-11 at 09:53 +0100, Toke Høiland-Jørgensen wrote:
>> Johannes Berg <johannes@...solutions.net> writes:
>> 
>> > On Tue, 2019-12-10 at 13:46 -0700, Jens Axboe wrote:
>> > > Hi,
>> > > 
>> > > Since the GRO issue got fixed, iwlwifi has worked fine for me.
>> > > However, on every boot, I get some warnings:
>> > > 
>> > > ------------[ cut here ]------------
>> > > STA b4:75:0e:99:1f:e0 AC 2 txq pending airtime underflow: 4294967088, 208
>> > 
>> > Yeah, we've seen a few reports of this.
>> 
>> FWIW I've tried reproducing but I don't get the error with the 8265 /
>> 8275 chip in my laptop. I've thought about sending a patch for mac80211
>> to just clear the tx_time_est field after calling
>> ieee80211_sta_update_pending_airtime() - that should prevent any errors
>> from double-reporting of skbs (which is what I'm guessing is going on
>> here).
>
> It does feel like it, but I'm not sure how that'd be possible?
>
> OK, I talked with Emmanuel and I think it's the GSO path - it'll end up
> with skb_clone() and then report both of them back.

Right, figured it was something like that; just couldn't find the place
in the driver where it did that from my cursory browsing.

> Regardless, I think I'll probably have to disable AQL and make it more
> opt-in for the driver - I found a bunch of other issues ...

Issues like what? Making it opt-in was going to be my backup plan; I was
kinda hoping we could work out any issues so it would be a "no harm"
kind of thing that could be left as always-on. Maybe that was a bit too
optimistic; but it's also a pain having to keep track of which drivers
have which features/fixes...

-Toke