From f4d08ddd3e60c79a141be36a5f3a7294c619291d Mon Sep 17 00:00:00 2001 From: Arik Nemtsov Date: Wed, 23 Feb 2011 00:22:24 +0200 Subject: [PATCH] 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: Arik Nemtsov Signed-off-by: Luciano Coelho --- drivers/net/wireless/wl12xx/main.c | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) diff --git a/drivers/net/wireless/wl12xx/main.c b/drivers/net/wireless/wl12xx/main.c index 13c7102f9864..9bb9ad31c2f5 100644 --- a/drivers/net/wireless/wl12xx/main.c +++ b/drivers/net/wireless/wl12xx/main.c @@ -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; } -- 2.30.2