ath9k: fix an issue in ath_atx_tid paused flag management

I noticed a possible issue in the paused flag management of the
ath_atx_tid data structure. In particular, in a noisy environment and
under heavy load, I observed that the AGGR session establishment could
fail several times consecutively causing values of the paused flag
greater than one for this TID (ath_tx_pause_tid is called more than
once from ath_tx_aggr_start).

Considering that the session for this TID can not be established also
after the mac80211 stack calls the ieee80211_agg_tx_operational() since
the ath_tx_aggr_resume() lowers the paused flag only by one.

This patch also replaces some BUG_ON calls with WARN_ON, as even if
these unlikely conditions happen, it's not fatal enough to justify a
BUG_ON.

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 8 insertions, 26 deletions

diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index 700ba8dee5a5..4dda14e36227 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -120,26 +120,14 @@ static void ath_tx_queue_tid(struct ath_txq *txq, struct ath_atx_tid *tid)
         list_add_tail(&ac->list, &txq->axq_acq);
 }
 
-static void ath_tx_pause_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
-{
-        struct ath_txq *txq = &sc->tx.txq[tid->ac->qnum];
-
-        spin_lock_bh(&txq->axq_lock);
-        tid->paused++;
-        spin_unlock_bh(&txq->axq_lock);
-}
-
 static void ath_tx_resume_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
 {
         struct ath_txq *txq = &sc->tx.txq[tid->ac->qnum];
 
-        BUG_ON(tid->paused <= 0);
-        spin_lock_bh(&txq->axq_lock);
-
-        tid->paused--;
+        WARN_ON(!tid->paused);
 
-        if (tid->paused > 0)
-                goto unlock;
+        spin_lock_bh(&txq->axq_lock);
+        tid->paused = false;
 
         if (list_empty(&tid->buf_q))
                 goto unlock;
@@ -157,15 +145,10 @@ static void ath_tx_flush_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
         struct list_head bf_head;
         INIT_LIST_HEAD(&bf_head);
 
-        BUG_ON(tid->paused <= 0);
-        spin_lock_bh(&txq->axq_lock);
+        WARN_ON(!tid->paused);
 
-        tid->paused--;
-
-        if (tid->paused > 0) {
-                spin_unlock_bh(&txq->axq_lock);
-                return;
-        }
+        spin_lock_bh(&txq->axq_lock);
+        tid->paused = false;
 
         while (!list_empty(&tid->buf_q)) {
                 bf = list_first_entry(&tid->buf_q, struct ath_buf, list);
@@ -811,7 +794,7 @@ void ath_tx_aggr_start(struct ath_softc *sc, struct ieee80211_sta *sta,
         an = (struct ath_node *)sta->drv_priv;
         txtid = ATH_AN_2_TID(an, tid);
         txtid->state |= AGGR_ADDBA_PROGRESS;
-        ath_tx_pause_tid(sc, txtid);
+        txtid->paused = true;
         *ssn = txtid->seq_start;
 }
 
@@ -835,10 +818,9 @@ void ath_tx_aggr_stop(struct ath_softc *sc, struct ieee80211_sta *sta, u16 tid)
                 return;
         }
 
-        ath_tx_pause_tid(sc, txtid);
-
         /* drop all software retried frames and mark this TID */
         spin_lock_bh(&txq->axq_lock);
+        txtid->paused = true;
         while (!list_empty(&txtid->buf_q)) {
                 bf = list_first_entry(&txtid->buf_q, struct ath_buf, list);
                 if (!bf_isretried(bf)) {