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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
To:     Rajkumar Manoharan <rmanohar@codeaurora.org>
Cc:     Jonathan Morton <chromatix99@gmail.com>, Kan Yan <kyan@google.com>,
        make-wifi-fast@lists.bufferbloat.net,
        linux-wireless-owner@vger.kernel.org,
        linux-wireless@vger.kernel.org, Felix Fietkau <nbd@nbd.name>
Subject: Re: [Make-wifi-fast] [PATCH RFC v4 3/4] mac80211: Add airtime accounting and scheduling to TXQs
In-Reply-To: <08dabe69e625c11f70b217ae9695c7f4@codeaurora.org>
References: <153711966150.9231.13481453399723518107.stgit@alrua-x1> <153711973134.9231.18038849900399644494.stgit@alrua-x1.karlstad.toke.dk> <826b6251746ee4d280d532f4ecdc5aa3@codeaurora.org> <87pnx0haud.fsf@toke.dk> <8f7145bf5abe50194bced025a5e739b9@codeaurora.org> <863bc54fbf04441d38dd53f523300a7e@codeaurora.org> <93015743-5D16-4D79-948F-E2F46CF2450A@toke.dk> <7ba8513b0ec5a7c35b396c7739fc2d7d@codeaurora.org> <87zhw2eyfo.fsf@toke.dk> <5d961a5f61de45b85b1b037bcef9270d@codeaurora.org> <44B09168-C08F-4C85-8D74-D576CCC79880@gmail.com> <586459da6ec36edc2284df8533915d62@codeaurora.org> <4929C006-3452-4C17-9500-8D7485EB538E@toke.dk> <0531def170ef7f9cadcf85a6dc9af22b@codeaurora.org> <87a7nwbvwu.fsf@toke.dk> <a5a7e11d6913c32385cc74ea3d0e1c76@codeaurora.org> <877ej0b2d8.fsf@toke.dk> <30cf3754fa970aa1af11791c2625a7c9@codeaurora.org> <08dabe69e625c11f70b217ae9695c7f4@codeaurora.org>
Date:   Wed, 03 Oct 2018 10:41:16 +0200
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Rajkumar Manoharan <rmanohar@codeaurora.org> writes:

> On 2018-10-02 16:07, Rajkumar Manoharan wrote:
>> On 2018-10-02 12:00, Toke H=C3=B8iland-J=C3=B8rgensen wrote:
>>> Rajkumar Manoharan <rmanohar@codeaurora.org> writes:
>>>> I noticed a race condition b/w sta cleanup and kick_airtime tasklet.
>>>>>> How do you plan to exit kick_airtime gracefully during sta_cleanup?
>>>>>=20
>>>>> Ah, right, there's a lot of stuff going on before we get to=20
>>>>> purge_txq.
>>>>> Hmm, I guess we should either make sure we remove the station from
>>>>> active_txqs earlier in the sta cleanup process, or maybe it'd enough=
=20
>>>>> to
>>>>> just check the removed flag in the tasklet?
>>>>>=20
>>>>> Does the below patch fix the issue?
>>>>>=20
>>>>=20
>>>> No. Attaching backtrace. Any clue?
>>>=20
>>> Ah, that's my bad. Just having a 'continue' there can make the=20
>>> function
>>> loop forever. Oops. Try something like this instead?
>>>=20
>>=20
>> But 'continue' also used in other places. Will give a try but I think=20
>> that
>> calling drv_wake_tx_queue within iteration is dangerous as it alters
>> the list. no?
>>=20
> How about below change? Just schedule first txq and remaining will be
> scheduled later by driver upon tx-compl.

Your mail client seems to be mangling the patch somewhat, but I think I
see what your intention is. And yeah, just waking a single TXQ and
letting TX-completion do the rest is a good idea; will fold that into
the next version :)

-Toke