On Tue, Dec 21, 2004 at 01:22:18AM +0100, Francois Romieu wrote:
> Matt Mackall <mpm@xxxxxxxxxxx> :
> > On Mon, Dec 20, 2004 at 09:42:08AM -0000, Mark Broadbent wrote:
> > >
> > > Exactly the same happens, I still get a 'NMI Watchdog detected LOCKUP'
> > > with the r8169 device using the above patch on top of 2.6.10-rc3-bk10.
> >
> > Ok, that suggests a problem localized to netpoll itself. Do you have
> > spinlock debugging turned on by any chance?
>
> Any chance of:
> 1 dev_queue_xmit
> 2 dev->xmit_lock taken
> 3 interruption
> 4 printk
> 5 netconsole write
> 6 dev->xmit_lock again
> 7 lockup
>
> ?
>
> This is probably the silly question of the day.
Maybe, but the answer isn't obvious to me at the moment as I haven't
been thinking about such stuff enough lately. Silly response of the
day:
Mark, can you try this (again completely untested, but at least
compiles) patch? I'm afraid I don't have a proper test rig to
reproduce this at the moment. This will attempt to grab the lock, and
if it fails, will check for recursion. Then it will try to print a
message on the local console, temporarily disabling netconsole to
allow the printk to get through..
Index: l/net/core/netpoll.c
===================================================================
--- l.orig/net/core/netpoll.c 2004-11-04 10:53:23.388610000 -0800
+++ l/net/core/netpoll.c 2004-12-20 16:45:40.212709000 -0800
@@ -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;
@@ -183,13 +185,24 @@
int status;
repeat:
- if(!np || !np->dev || !netif_running(np->dev)) {
+ if(!np || !np->dev || !netif_running(np->dev) || netpoll_kill) {
__kfree_skb(skb);
return;
}
- spin_lock(&np->dev->xmit_lock);
- np->dev->xmit_lock_owner = smp_processor_id();
+ if(spin_trylock(&np->dev->xmit_lock))
+ np->dev->xmit_lock_owner = smp_processor_id();
+ else {
+ if(np->dev->xmit_lock_owner == smp_processor_id()) {
+ netpoll_kill = 1;
+ __kfree_skb(skb);
+ printk("Tried to recursively get dev->xmit_lock");
+ netpoll_kill = 0;
+ return;
+ }
+ spin_lock(&np->dev->xmit_lock);
+
+ }
/*
* network drivers do not expect to be called if the queue is
--
Mathematics is the supreme nostalgia of our time.
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