netdev - Re: Sundance network driver (D-Link DFE-580TX) timeouts rendering interface unusable

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Message-ID: <1327919763.2288.26.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Mon, 30 Jan 2012 11:36:03 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Denis Kirjanov <kirjanov@...il.com>
Cc:	Ben Hutchings <ben@...adent.org.uk>,
	"Mike ." <mike-bugreport@...mail.com>, 656476@...s.debian.org,
	netdev <netdev@...r.kernel.org>
Subject: Re: Sundance network driver (D-Link DFE-580TX) timeouts rendering
 interface unusable

Le lundi 30 janvier 2012 à 11:14 +0100, Eric Dumazet a écrit :
> Le lundi 30 janvier 2012 à 12:51 +0300, Denis Kirjanov a écrit :
> > I'll check this out. After kernel.org was cracked I've missed
> > @kernel.org mail account.
> 
> 
> At first glance, start_tx() is racy against TX completion.
> 
> It does :
> 
>         if (np->cur_tx - np->dirty_tx < TX_QUEUE_LEN - 1 &&
>             !netif_queue_stopped(dev)) {
>                 /* do nothing */
>         } else {
>                 netif_stop_queue (dev);
>         }
> 
> So it can call netif_stop_queue() while TX completion handler did a
> cleanup of all queued packets right before.
> 
> 
> Note intr_handler() doesnt hold the queue spinlock when it does :
> 
>                 if (netif_queue_stopped(dev) &&
>                         np->cur_tx - np->dirty_tx < TX_QUEUE_LEN - 4) {
>                         /* The ring is no longer full, clear busy flag. */
>                         netif_wake_queue (dev);
>                 }
> 

So I would try following patch :

 drivers/net/ethernet/dlink/sundance.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/dlink/sundance.c b/drivers/net/ethernet/dlink/sundance.c
index 28a3a9b..c671a6c 100644
--- a/drivers/net/ethernet/dlink/sundance.c
+++ b/drivers/net/ethernet/dlink/sundance.c
@@ -1099,11 +1099,13 @@ start_tx (struct sk_buff *skb, struct net_device *dev)
 	tasklet_schedule(&np->tx_tasklet);
 
 	/* On some architectures: explicitly flush cache lines here. */
-	if (np->cur_tx - np->dirty_tx < TX_QUEUE_LEN - 1 &&
-	    !netif_queue_stopped(dev)) {
-		/* do nothing */
-	} else {
-		netif_stop_queue (dev);
+	if (np->cur_tx - np->dirty_tx >= TX_QUEUE_LEN - 1) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&np->lock, flags);
+		if (np->cur_tx - np->dirty_tx >= TX_QUEUE_LEN - 1)
+			netif_stop_queue(dev);
+		spin_unlock_irqrestore(&np->lock, flags);
 	}
 	if (netif_msg_tx_queued(np)) {
 		printk (KERN_DEBUG


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