ar9170: atomic pending A-MPDU counter

A ref-counting bug emerged after testing ar9170usb's HT
implementation on a bigger SMP/SMT system without the usual
_debugging_ overhead.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 7 insertions, 6 deletions

diff --git a/drivers/net/wireless/ath/ar9170/ar9170.h b/drivers/net/wireless/ath/ar9170/ar9170.h
index ec034af26980..9f9459860d82 100644
--- a/drivers/net/wireless/ath/ar9170/ar9170.h
+++ b/drivers/net/wireless/ath/ar9170/ar9170.h
@@ -231,7 +231,7 @@ struct ar9170 {
         struct sk_buff_head tx_status_ampdu;
         spinlock_t tx_ampdu_list_lock;
         struct list_head tx_ampdu_list;
-        unsigned int tx_ampdu_pending;
+        atomic_t tx_ampdu_pending;
 
         /* rxstream mpdu merge */
         struct ar9170_rxstream_mpdu_merge rx_mpdu;
diff --git a/drivers/net/wireless/ath/ar9170/main.c b/drivers/net/wireless/ath/ar9170/main.c
index de0ba2bf7691..7e59b82e64d3 100644
--- a/drivers/net/wireless/ath/ar9170/main.c
+++ b/drivers/net/wireless/ath/ar9170/main.c
@@ -414,9 +414,9 @@ static void ar9170_tx_ampdu_callback(struct ar9170 *ar, struct sk_buff *skb)
 
         skb_queue_tail(&ar->tx_status_ampdu, skb);
         ar9170_tx_fake_ampdu_status(ar);
-        ar->tx_ampdu_pending--;
 
-        if (!list_empty(&ar->tx_ampdu_list) && !ar->tx_ampdu_pending)
+        if (atomic_dec_and_test(&ar->tx_ampdu_pending) &&
+            !list_empty(&ar->tx_ampdu_list))
                 ar9170_tx_ampdu(ar);
 }
 
@@ -1248,6 +1248,7 @@ static int ar9170_op_start(struct ieee80211_hw *hw)
         ar->global_ampdu_density = 6;
         ar->global_ampdu_factor = 3;
 
+        atomic_set(&ar->tx_ampdu_pending, 0);
         ar->bad_hw_nagger = jiffies;
 
         err = ar->open(ar);
@@ -1773,7 +1774,7 @@ static void ar9170_tx(struct ar9170 *ar)
                                           msecs_to_jiffies(AR9170_TX_TIMEOUT);
 
                         if (arinfo->flags == AR9170_TX_FLAG_BLOCK_ACK)
-                                ar->tx_ampdu_pending++;
+                                atomic_inc(&ar->tx_ampdu_pending);
 
 #ifdef AR9170_QUEUE_DEBUG
                         printk(KERN_DEBUG "%s: send frame q:%d =>\n",
@@ -1784,7 +1785,7 @@ static void ar9170_tx(struct ar9170 *ar)
                         err = ar->tx(ar, skb);
                         if (unlikely(err)) {
                                 if (arinfo->flags == AR9170_TX_FLAG_BLOCK_ACK)
-                                        ar->tx_ampdu_pending--;
+                                        atomic_dec(&ar->tx_ampdu_pending);
 
                                 frames_failed++;
                                 dev_kfree_skb_any(skb);
@@ -1931,7 +1932,7 @@ int ar9170_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
         if (info->flags & IEEE80211_TX_CTL_AMPDU) {
                 bool run = ar9170_tx_ampdu_queue(ar, skb);
 
-                if (run || !ar->tx_ampdu_pending)
+                if (run || !atomic_read(&ar->tx_ampdu_pending))
                         ar9170_tx_ampdu(ar);
         } else {
                 unsigned int queue = skb_get_queue_mapping(skb);