Commit f4d08ddd authored by Arik Nemtsov's avatar Arik Nemtsov Committed by Luciano Coelho

wl12xx: fix potential race condition with TX queue watermark

Check the conditions for the high/low TX queue watermarks when the
spin-lock is taken. This prevents race conditions as tx_queue_count and
the flag checked are only modified when the spin-lock is taken.

The following race was in mind:
- Queues are almost full and wl1271_op_tx() will stop the queues, but it
  doesn't get the spin-lock yet.
- (on another CPU) tx_work_locked() dequeues 15 skbs from this queue and
  tx_queue_count is updated to reflect this
- wl1271_op_tx() does not check tx_queue_count after taking the
  spin-lock and incorrectly stops the queue.
Signed-off-by: default avatarArik Nemtsov <arik@wizery.com>
Signed-off-by: default avatarLuciano Coelho <coelho@ti.com>
parent 6dc9fb3c
...@@ -987,6 +987,17 @@ static int wl1271_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb) ...@@ -987,6 +987,17 @@ static int wl1271_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
spin_lock_irqsave(&wl->wl_lock, flags); spin_lock_irqsave(&wl->wl_lock, flags);
wl->tx_queue_count++; wl->tx_queue_count++;
/*
* The workqueue is slow to process the tx_queue and we need stop
* the queue here, otherwise the queue will get too long.
*/
if (wl->tx_queue_count >= WL1271_TX_QUEUE_HIGH_WATERMARK) {
wl1271_debug(DEBUG_TX, "op_tx: stopping queues");
ieee80211_stop_queues(wl->hw);
set_bit(WL1271_FLAG_TX_QUEUE_STOPPED, &wl->flags);
}
spin_unlock_irqrestore(&wl->wl_lock, flags); spin_unlock_irqrestore(&wl->wl_lock, flags);
/* queue the packet */ /* queue the packet */
...@@ -1001,19 +1012,6 @@ static int wl1271_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb) ...@@ -1001,19 +1012,6 @@ static int wl1271_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
if (!test_bit(WL1271_FLAG_FW_TX_BUSY, &wl->flags)) if (!test_bit(WL1271_FLAG_FW_TX_BUSY, &wl->flags))
ieee80211_queue_work(wl->hw, &wl->tx_work); ieee80211_queue_work(wl->hw, &wl->tx_work);
/*
* The workqueue is slow to process the tx_queue and we need stop
* the queue here, otherwise the queue will get too long.
*/
if (wl->tx_queue_count >= WL1271_TX_QUEUE_HIGH_WATERMARK) {
wl1271_debug(DEBUG_TX, "op_tx: stopping queues");
spin_lock_irqsave(&wl->wl_lock, flags);
ieee80211_stop_queues(wl->hw);
set_bit(WL1271_FLAG_TX_QUEUE_STOPPED, &wl->flags);
spin_unlock_irqrestore(&wl->wl_lock, flags);
}
return NETDEV_TX_OK; return NETDEV_TX_OK;
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment