[PATCH AUTOSEL for 4.14 56/97] rt2x00: do not pause queue unconditionally on error path

Sasha Levin
2018-03-19T21:59:56Z

From: Stanislaw Gruszka <sgruszka@redhat.com>

[ 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@redhat.com>
Tested-by: Enrico Mioso <mrkiko.rs@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
drivers/net/wireless/ralink/rt2x00/rt2x00mac.c | 22 ++++++++++++++--------
1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00mac.c b/drivers/net/wireless/ralink/rt2x00/rt2x00mac.c
index ecc96312a370..6fe0c6abe0d6 100644
--- 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 *hw,
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 *hw,

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);
}
--
2.14.1