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

From: "Toke Høiland-Jørgensen" <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
Date: Tue, 02 Oct 2018 10:22:09 +0200	[thread overview]
Message-ID: <87a7nwbvwu.fsf@toke.dk> (raw)
In-Reply-To: <0531def170ef7f9cadcf85a6dc9af22b@codeaurora.org>

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?

-Toke

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 9c889da48ef0..8fa3c09d041c 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)
+			continue;
+
 		if (sta->airtime[ac].deficit >= 0) {
 			seen_eligible = true;
 
