On a WL-330N3G device, these patches seems to make the situation much better.
In other words, I wasn't able to reproduce the stall on this chipset.
On MT7620 a stall was never seen directly, but tests with these patches revealed no stall.
So I think it's good to have these merged.
Tested-by: Enrico Mioso <mrkiko.rs@xxxxxxxxx>
On Tue, 19 Dec 2017, Stanislaw Gruszka wrote:
Date: Tue, 19 Dec 2017 12:33:56
From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
To: linux-wireless@xxxxxxxxxxxxxxx
Cc: Helmut Schaa <helmut.schaa@xxxxxxxxxxxxxx>,
Enrico Mioso <mrkiko.rs@xxxxxxxxx>, Daniel Golle <daniel@xxxxxxxxxxxxxx>,
Felix Fietkau <nbd@xxxxxxxx>, Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Subject: [PATCH 2/2] rt2x00: do not pause queue unconditionally on error path
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>
---
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 c8a6f163102f..a971bc7a6b63 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2x00mac.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2x00mac.c
@@ -142,22 +142,28 @@ 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;
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);
}
--
1.9.3
