[PATCH] ipw2200: stop netdev queue if h/w doesn't have space for new packets

The patch roll back the change we made to support for the ability to
start/stop independent Tx queues within a single net device in order to
support 802.11e QoS. We need to be able to indicate to the upper layers
that packets of a given priority can not be sent any more without halting
transmission of all packets, and without rescheduling high priority packets
down to the next priority level.

So we return NETDEV_TX_BUSY in this case and rely on the stack would
take care of rescheduling... which it apparently does immediately and
consumes the CPU. This caused the ksoftirqd kernel thread consuming almost
all the CPU...

To put the code back to the way it was before we made these changes we
put the call netif_queue_stop back in ipw_tx_skb.  This effectively
disables multiple priority based transmit queues for 802.11e, but given
that its broken anyway...

Signed-off-by: James Ketrenos <jketreno@linux.intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ipw2200.c

@@ -9648,11 +9648,6 @@ static int ipw_tx_skb(struct ipw_priv *priv, struct ieee80211_txb *txb,
 	u16 remaining_bytes;
 	int fc;
 
-	/* If there isn't room in the queue, we return busy and let the
-	 * network stack requeue the packet for us */
-	if (ipw_queue_space(q) < q->high_mark)
-		return NETDEV_TX_BUSY;
-
 	switch (priv->ieee->iw_mode) {
 	case IW_MODE_ADHOC:
 		hdr_len = IEEE80211_3ADDR_LEN;
@@ -9818,6 +9813,9 @@ static int ipw_tx_skb(struct ipw_priv *priv, struct ieee80211_txb *txb,
 	q->first_empty = ipw_queue_inc_wrap(q->first_empty, q->n_bd);
 	ipw_write32(priv, q->reg_w, q->first_empty);
 
+	if (ipw_queue_space(q) < q->high_mark)
+		netif_stop_queue(priv->net_dev);
+
 	return NETDEV_TX_OK;
 
       drop: