p54: tx refused but queue active

In the mainline kernel, p54usb will fail because the TX queue length can
become < 0. This problem has been reported as Bugzilla #13725. The failure
is expressed by the following message in the logs:

WARNING: at net/mac80211/tx.c:1325 ieee80211_tx+0x23c/0x298 [mac80211]()
Hardware name: HP Pavilion dv2700 Notebook PC
tx refused but queue active

This problem has been recently observed in the wireless-testing tree, where
a full solution is being tested. That fix is too invasive for 2.6.31-rcX,
but the simple change supplied here will prevent the failure.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/net/wireless/p54/p54common.c b/drivers/net/wireless/p54/p54common.c
index 48d81d98e12d..22ca122bd798 100644
--- a/drivers/net/wireless/p54/p54common.c
+++ b/drivers/net/wireless/p54/p54common.c
@@ -912,13 +912,14 @@ static void p54_rx_frame_sent(struct ieee80211_hw *dev, struct sk_buff *skb)
                 }
 
                 __skb_unlink(entry, &priv->tx_queue);
-                spin_unlock_irqrestore(&priv->tx_queue.lock, flags);
 
                 frame_len = entry->len;
                 entry_hdr = (struct p54_hdr *) entry->data;
                 entry_data = (struct p54_tx_data *) entry_hdr->data;
-                priv->tx_stats[entry_data->hw_queue].len--;
+                if (priv->tx_stats[entry_data->hw_queue].len)
+                        priv->tx_stats[entry_data->hw_queue].len--;
                 priv->stats.dot11ACKFailureCount += payload->tries - 1;
+                spin_unlock_irqrestore(&priv->tx_queue.lock, flags);
 
                 /*
                  * Frames in P54_QUEUE_FWSCAN and P54_QUEUE_BEACON are