spin lock sched lock held by 0xffffff007b712250 for > 5 seconds

[Willem Jan Withagen]

From: "Robert Watson" <rwatson at freebsd.org>
> On Fri, 16 Jul 2004, Willem Jan Withagen wrote:
> 
> > After todays kernelbuild the system seem to be a lot better...
> > It can take quite some buildworld abuse, but still:
> > 
> > spin lock sched lock held by 0xffffff007b712250 for > 5 seconds
> > panic: spin lock held too long
> > cpuid = 1;
> > KDB: enter: panic
> > 
> > But I'm not shure what I could/should do now, since the KDB
> > introduction.  Normally I'd expect to see:  db>
> 
> We have trouble entering the debugger when in a critical section/and or
> have sched_lock held -- I think this is because we try to halt the other
> CPUs and that gets nastily stuck in some form.  We need to fix this.
> 
> This could well be a symptom of some of the other hangs we've been seeing,
> and I've seen similar things on my test box with preemption enabled.

To be honest, it is a lot better than at the beginning of the week.
Anything I can do to help debug either of them??
Suggestions where/what to look for?

--WjW