This is a note to let you know that I've just added the patch titled rt2x00: do not pause queue unconditionally on error path to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: rt2x00-do-not-pause-queue-unconditionally-on-error-path.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Mon Apr 9 13:58:16 CEST 2018 From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx> Date: Tue, 19 Dec 2017 12:33:56 +0100 Subject: rt2x00: do not pause queue unconditionally on error path From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx> [ Upstream commit 6dd80efd75ce7c2dbd9f117cf585ee2b33a42ee1 ] Pausing queue without checking threshold is racy with txdone path. Moreover we do not need pause queue on any error, but only if queue is full - in case when we send RTS frame ( other cases of almost full queue are already handled in rt2x00queue_write_tx_frame() ). Patch fixes of theoretically possible problem of pausing empty queue. Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx> Tested-by: Enrico Mioso <mrkiko.rs@xxxxxxxxx> Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/net/wireless/ralink/rt2x00/rt2x00mac.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) --- a/drivers/net/wireless/ralink/rt2x00/rt2x00mac.c +++ b/drivers/net/wireless/ralink/rt2x00/rt2x00mac.c @@ -142,15 +142,25 @@ void rt2x00mac_tx(struct ieee80211_hw *h if (!rt2x00dev->ops->hw->set_rts_threshold && (tx_info->control.rates[0].flags & (IEEE80211_TX_RC_USE_RTS_CTS | IEEE80211_TX_RC_USE_CTS_PROTECT))) { - if (rt2x00queue_available(queue) <= 1) - goto exit_fail; + if (rt2x00queue_available(queue) <= 1) { + /* + * Recheck for full queue under lock to avoid race + * conditions with rt2x00lib_txdone(). + */ + spin_lock(&queue->tx_lock); + if (rt2x00queue_threshold(queue)) + rt2x00queue_pause_queue(queue); + spin_unlock(&queue->tx_lock); + + goto exit_free_skb; + } if (rt2x00mac_tx_rts_cts(rt2x00dev, queue, skb)) - goto exit_fail; + goto exit_free_skb; } if (unlikely(rt2x00queue_write_tx_frame(queue, skb, control->sta, false))) - goto exit_fail; + goto exit_free_skb; /* * Pausing queue has to be serialized with rt2x00lib_txdone(). Note @@ -164,10 +174,6 @@ void rt2x00mac_tx(struct ieee80211_hw *h return; - exit_fail: - spin_lock(&queue->tx_lock); - rt2x00queue_pause_queue(queue); - spin_unlock(&queue->tx_lock); exit_free_skb: ieee80211_free_txskb(hw, skb); } Patches currently in stable-queue which might be from sgruszka@xxxxxxxxxx are queue-4.14/rt2x00-do-not-pause-queue-unconditionally-on-error-path.patch