Ingo Molnar wrote:
> disable_irq() should work fine though. (it doesnt disable local
> interrupts, it only disables that particular irq line.) So something
> else disabled interrupts - ah, netconsole.c itself. Does the patch below
> fix things up for you?
> 
> 	Ingo
 > [patch snipped]

That patch was not enough. The BUGs were still showing up the same as 
before.
I tried to debug it myself. I've found an interesting thing in 
kernel/printk.c:release_console_sem(). There is the following sequence:

   spin_lock_irqsave(&logbuf_lock, flags);
   /* ... some code ... */
   spin_unlock(&logbuf_lock);
   call_console_drivers(...);
   local_irq_restore(flags);

I know very little about locking, but I didn't like this two-phased 
unlock. So I replaced it with a single spin_unlock_irqrestore. Patch 
attached.
I'm almost certain that there is a reason for the two-phased unlocking 
and that this patch will break something, but so far it works for me. 
netconsole now works without complaining.

Michal