Re: Lockup with 2.6.9-ac15 related to netconsole

[Francois Romieu <romieu@xxxxxxxxxxxxx>]

Mark Broadbent <markb@xxxxxxxxxxxxxx> :
[...]
> 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();
 
        /*