[PATCH 2/2] p54: enforce strict tx_queue limits

[PATCH 2/2] p54: enforce strict tx_queue limits

[Christian Lamparter]

The patch fixes an old FIXME in p54pci.c by moving the "queue full" 
check into the common library, where we can deal with it properly.

Signed-off-by: Christian Lamparter <chunkeey@web.de>
---
diff -Nurp a/drivers/net/wireless/p54/p54common.c b/drivers/net/wireless/p54/p54common.c
--- a/drivers/net/wireless/p54/p54common.c	2008-12-09 20:13:56.467888032 +0100
+++ b/drivers/net/wireless/p54/p54common.c	2008-12-09 20:49:21.235888230 +0100
@@ -889,7 +889,27 @@ static int p54_assign_address(struct iee
 		return -EINVAL;
 
 	spin_lock_irqsave(&priv->tx_queue.lock, flags);
+
 	left = skb_queue_len(&priv->tx_queue);
+	if (unlikely(left >= 28)) {
+		/*
+		 * The tx_queue is nearly full!
+		 * We have throttle normal data traffic, because we must
+		 * have a few spare slots for control frames left.
+		 */
+		ieee80211_stop_queues(dev);
+
+		if (unlikely(left == 32)) {
+			/*
+			 * The tx_queue is now really full.
+			 *
+			 * TODO: check if the device has crashed and reset it.
+			 */
+			spin_unlock_irqrestore(&priv->tx_queue.lock, flags);
+			return -ENOSPC;
+		}
+	}
+
 	while (left--) {
 		u32 hole_size;
 		info = IEEE80211_SKB_CB(entry);
@@ -918,7 +938,7 @@ static int p54_assign_address(struct iee
 	if (!target_skb) {
 		spin_unlock_irqrestore(&priv->tx_queue.lock, flags);
 		ieee80211_stop_queues(dev);
-		return -ENOMEM;
+		return -ENOSPC;
 	}
 
 	info = IEEE80211_SKB_CB(skb);
diff -Nurp a/drivers/net/wireless/p54/p54pci.c b/drivers/net/wireless/p54/p54pci.c
--- a/drivers/net/wireless/p54/p54pci.c	2008-12-09 20:05:21.251888445 +0100
+++ b/drivers/net/wireless/p54/p54pci.c	2008-12-07 22:04:45.952897552 +0100
@@ -332,13 +332,6 @@ static void p54p_tx(struct ieee80211_hw 
 
 	P54P_WRITE(dev_int, cpu_to_le32(ISL38XX_DEV_INT_UPDATE));
 	P54P_READ(dev_int);
-
-	/* FIXME: unlikely to happen because the device usually runs out of
-	   memory before we fill the ring up, but we can make it impossible */
-	if (idx - device_idx > ARRAY_SIZE(ring_control->tx_data) - 2) {
-		p54_free_skb(dev, skb);
-		printk(KERN_INFO "%s: tx overflow.\n", wiphy_name(dev->wiphy));
-	}
 }
 
 static void p54p_stop(struct ieee80211_hw *dev)

Re: [PATCH 2/2] p54: enforce strict tx_queue limits

[Larry Finger]

Christian Lamparter wrote:
> The patch fixes an old FIXME in p54pci.c by moving the "queue full" 
> check into the common library, where we can deal with it properly.
> 
> Signed-off-by: Christian Lamparter <chunkeey@web.de>
> ---
> diff -Nurp a/drivers/net/wireless/p54/p54common.c b/drivers/net/wireless/p54/p54common.c
> --- a/drivers/net/wireless/p54/p54common.c	2008-12-09 20:13:56.467888032 +0100
> +++ b/drivers/net/wireless/p54/p54common.c	2008-12-09 20:49:21.235888230 +0100
> @@ -889,7 +889,27 @@ static int p54_assign_address(struct iee
>  		return -EINVAL;
>  
>  	spin_lock_irqsave(&priv->tx_queue.lock, flags);
> +
>  	left = skb_queue_len(&priv->tx_queue);
> +	if (unlikely(left >= 28)) {
> +		/*
> +		 * The tx_queue is nearly full!
> +		 * We have throttle normal data traffic, because we must
> +		 * have a few spare slots for control frames left.
> +		 */
> +		ieee80211_stop_queues(dev);

I do not intend this as a criticism of the patch, but how do the queues get
restarted after this?

Larry

Re: [PATCH 2/2] p54: enforce strict tx_queue limits

[Christian Lamparter]

On Wednesday 10 December 2008 03:39:00 Larry Finger wrote:
> Christian Lamparter wrote:
> > The patch fixes an old FIXME in p54pci.c by moving the "queue full" 
> > check into the common library, where we can deal with it properly.
> > 
> > Signed-off-by: Christian Lamparter <chunkeey@web.de>
> > ---
> > diff -Nurp a/drivers/net/wireless/p54/p54common.c b/drivers/net/wireless/p54/p54common.c
> > --- a/drivers/net/wireless/p54/p54common.c	2008-12-09 20:13:56.467888032 +0100
> > +++ b/drivers/net/wireless/p54/p54common.c	2008-12-09 20:49:21.235888230 +0100
> > @@ -889,7 +889,27 @@ static int p54_assign_address(struct iee
> >  		return -EINVAL;
> >  
> >  	spin_lock_irqsave(&priv->tx_queue.lock, flags);
> > +
> >  	left = skb_queue_len(&priv->tx_queue);
> > +	if (unlikely(left >= 28)) {
> > +		/*
> > +		 * The tx_queue is nearly full!
> > +		 * We have throttle normal data traffic, because we must
> > +		 * have a few spare slots for control frames left.
> > +		 */
> > +		ieee80211_stop_queues(dev);
> 
> I do not intend this as a criticism of the patch, but how do the queues get
> restarted after this?
> 

The idea is that p54_free_skb & p54_rx_frame_sent callbacks, which are
called whenever the firmware has finished processing a "device control"
or wifi frames. (And at that point there're atleast 28 pending frames,
so one should eventually get freed unless the firmware crashed!)

These routines unlink the frame form the tx_queue and call
p54_wake_free_queues if there's enough space for a new data frame.

Regards,
	Chr