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Date:   Fri, 28 Sep 2018 02:44:19 -0700
From:   Rajkumar Manoharan <rmanohar@codeaurora.org>
To:     =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
Cc:     linux-wireless@vger.kernel.org,
        make-wifi-fast@lists.bufferbloat.net, Felix Fietkau <nbd@nbd.name>,
        Kan Yan <kyan@google.com>, linux-wireless-owner@vger.kernel.org
Subject: Re: [PATCH RFC v4 3/4] mac80211: Add airtime accounting and
 scheduling to TXQs
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On 2018-09-28 02:27, Rajkumar Manoharan wrote:
> On 2018-09-28 00:51, Toke Høiland-Jørgensen wrote:
>> On 28 September 2018 07:29:03 CEST, Rajkumar Manoharan
>> <rmanohar@codeaurora.org> wrote:
>>> On 2018-09-26 17:09, Rajkumar Manoharan wrote:
>>>> On 2018-09-26 02:22, Toke Høiland-Jørgensen wrote:
>>>>> Rajkumar Manoharan <rmanohar@codeaurora.org> writes:
>>> 
>>>> :( Yeah... I got confused with attached soft lockup in ARM platform.
>>>> 
>>> Toke,
>>> 
>>> Cause for the soft lockup exposed in multi client scenario is due to
>>> mixed order of fq_lock and active_txqs_lock. In wake_tx_queue or
>>> push_pending
>>> case, driver acquires active_txq_lock first by schedule_start and
>>> followed by
>>> fq_lock in tx_dequeue. The same order should be maintained in sta
>>> cleanup.
>>> Below change fixed the issue.
>> 
>> Ah, great find! I'll fold this into the next version, thanks!
>> 
> 
> One more thing. As I mentioned earlier, scheduling wake_txqs_tasklet
> is heavy load and causing random rcu stall issue. Hence I added
> another API to schedule throttled txqs once for all. Also I did
> a cleanup in kick_airtime by traversing list only once. With these
> changes I don't see rcu stall issue. Please review and fold them as 
> well.
> 
Correction in patch. new API schedule kick_aitime tasklet not 
wake_txq_tasklet.

+void ieee80211_txq_schedule_throttled(struct ieee80211_hw *hw)
+{
+       struct ieee80211_local *local = hw_to_local(hw);
+
+       tasklet_schedule(&local->kick_airtime);
+}

-Rajkumar