Re: Lockup with 2.6.9-ac15 related to netconsole

[Francois Romieu <romieu@fr.zoreil.com>]

Mark Broadbent <markb@wetlettuce.com> :
[...]
> OK, patch applied and spinlock debugging enabled.  Testing with eth1
> (r1869) doesn'tyield any additional messages, just the standard
> 'NMI Watchdog detected lockup'.

Does the modified version below trigger _exactly_ the same hang ?

--- net/core/netpoll.c	2004-12-21 13:09:51.000000000 +0100
+++ net/core/netpoll.c	2004-12-21 13:27:01.000000000 +0100
@@ -31,6 +31,8 @@
 #define MAX_SKBS 32
 #define MAX_UDP_CHUNK 1460
 
+static int netpoll_kill;
+
 static spinlock_t skb_list_lock = SPIN_LOCK_UNLOCKED;
 static int nr_skbs;
 static struct sk_buff *skbs;
@@ -184,11 +186,21 @@ void netpoll_send_skb(struct netpoll *np
 
 repeat:
 	if(!np || !np->dev || !netif_running(np->dev)) {
+too_bad:
 		__kfree_skb(skb);
 		return;
 	}
 
-	spin_lock(&np->dev->xmit_lock);
+	if (!spin_trylock(&np->dev->xmit_lock)) {
+		netpoll_kill = 1;
+		goto too_bad;
+	}
+
+	if (netpoll_kill) {
+		if (net_ratelimit())
+			printk(KERN_ERR "netconsole raced");
+		netpoll_kill = 0;
+	}
 	np->dev->xmit_lock_owner = smp_processor_id();
 
 	/*