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Date:   Tue, 02 Oct 2018 16:07:34 -0700
From:   Rajkumar Manoharan <rmanohar@codeaurora.org>
To:     =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
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: <877ej0b2d8.fsf@toke.dk>
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On 2018-10-02 12:00, Toke Høiland-Jørgensen 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?
>>> 
>>> Ah, right, there's a lot of stuff going on before we get to 
>>> 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 
>>> to
>>> just check the removed flag in the tasklet?
>>> 
>>> Does the below patch fix the issue?
>>> 
>> 
>> No. Attaching backtrace. Any clue?
> 
> Ah, that's my bad. Just having a 'continue' there can make the function
> loop forever. Oops. Try something like this instead?
> 

But 'continue' also used in other places. Will give a try but I think 
that
calling drv_wake_tx_queue within iteration is dangerous as it alters the 
list. no?

-Rajkumar