[PATCH] ath9k: Don't trust TX status TID number when reporting airtime

[PATCH] ath9k: Don't trust TX status TID number when reporting airtime

[Toke Høiland-Jørgensen]

As already noted a comment in ath_tx_complete_aggr(), the hardware will
occasionally send a TX status with the wrong tid number. If we trust the
value, airtime usage will be reported to the wrong AC, which can cause the
deficit on that AC to become very low, blocking subsequent attempts to
transmit.

To fix this, account airtime usage to the TID number from the original skb,
instead of the one in the hardware TX status report.

Reported-by: Miguel Catalan Cid <miguel.catalan@i2cat.net>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
I haven't been able to confirm that this also affects the old in-driver
airtime scheduler, but I suspect it does, so I'll send a follow-up patch
to stable once this has been merged.

 drivers/net/wireless/ath/ath9k/xmit.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index 773d428ff1b0..1c91eda0ba51 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -668,7 +668,8 @@ static bool bf_is_ampdu_not_probing(struct ath_buf *bf)
 static void ath_tx_count_airtime(struct ath_softc *sc,
 				 struct ieee80211_sta *sta,
 				 struct ath_buf *bf,
-				 struct ath_tx_status *ts)
+				 struct ath_tx_status *ts,
+				 u8 tid)
 {
 	u32 airtime = 0;
 	int i;
@@ -679,7 +680,7 @@ static void ath_tx_count_airtime(struct ath_softc *sc,
 		airtime += rate_dur * bf->rates[i].count;
 	}
 
-	ieee80211_sta_register_airtime(sta, ts->tid, airtime, 0);
+	ieee80211_sta_register_airtime(sta, tid, airtime, 0);
 }
 
 static void ath_tx_process_buffer(struct ath_softc *sc, struct ath_txq *txq,
@@ -709,7 +710,7 @@ static void ath_tx_process_buffer(struct ath_softc *sc, struct ath_txq *txq,
 	if (sta) {
 		struct ath_node *an = (struct ath_node *)sta->drv_priv;
 		tid = ath_get_skb_tid(sc, an, bf->bf_mpdu);
-		ath_tx_count_airtime(sc, sta, bf, ts);
+		ath_tx_count_airtime(sc, sta, bf, ts, tid->tidno);
 		if (ts->ts_status & (ATH9K_TXERR_FILT | ATH9K_TXERR_XRETRY))
 			tid->clear_ps_filter = true;
 	}
-- 
2.21.0

Re: [PATCH] ath9k: Don't trust TX status TID number when reporting airtime

[Kalle Valo]

Toke Høiland-Jørgensen wrote:

> As already noted a comment in ath_tx_complete_aggr(), the hardware will
> occasionally send a TX status with the wrong tid number. If we trust the
> value, airtime usage will be reported to the wrong AC, which can cause the
> deficit on that AC to become very low, blocking subsequent attempts to
> transmit.
> 
> To fix this, account airtime usage to the TID number from the original skb,
> instead of the one in the hardware TX status report.
> 
> Reported-by: Miguel Catalan Cid <miguel.catalan@i2cat.net>
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

Patch applied to ath-next branch of ath.git, thanks.

389b72e58259 ath9k: Don't trust TX status TID number when reporting airtime

-- 
https://patchwork.kernel.org/patch/10843731/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches