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

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

drivers/net/wireless/wl12xx/main.c

+11 −13
Original line number Diff line number Diff line
@@ -987,6 +987,17 @@ static int wl1271_op_tx(struct ieee80211_hw *hw, struct sk_buff *skb) 


	spin_lock_irqsave(&wl->wl_lock, flags);

	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);



	/* queue the packet */
@@ -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))

		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;

}