Re: [Make-wifi-fast] [PATCH RFC v4 3/4] mac80211: Add airtime accounting and scheduling to TXQs

["Toke Høiland-Jørgensen" <toke@toke.dk>]

Rajkumar Manoharan <rmanohar@codeaurora.org> writes:

> On 2018-10-02 01:22, Toke Høiland-Jørgensen wrote:
>> Rajkumar Manoharan <rmanohar@codeaurora.org> writes:
>> 
>>>> Great! I'll fold in the rest, test it with ath9k and submit as a 
>>>> proper
>>>> patch :)
>>>> 
>>> Toke,
>>> 
>>> 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?

-Toke


diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index eb77cf588d69..b30a4fac1d60 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -258,6 +258,9 @@ static void __ieee80211_kick_airtime(struct ieee80211_local *local, int ac)
 
 		sta = container_of(txqi->txq.sta, struct sta_info, sta);
 
+		if (sta->removed)
+			goto out_reschedule;
+
 		if (sta->airtime[ac].deficit >= 0) {
 			seen_eligible = true;
 
@@ -288,7 +291,13 @@ static void __ieee80211_kick_airtime(struct ieee80211_local *local, int ac)
 	}
  out:
 	rcu_read_unlock();
 	spin_unlock_bh(&local->active_txq_lock[ac]);
+	return;
+
+ out_reschedule:
+	rcu_read_unlock();
+	spin_unlock_bh(&local->active_txq_lock[ac]);
+	tasklet_schedule(&local->airtime_tasklet);
 }
 
 void ieee80211_kick_airtime(unsigned long data)