I'm working on a system that is using a bit too much stack to work 
reliably with 4K stacks (OpenSSI with DRBD for the root filesystem 
replication) and I find that the CONFIG_DEBUG_STACKOVERFLOW stuff works 
rather poorly - often the stack dump will cause a stack overflow itself.

Here's a little patch to irq.c to make stack overflow dumps use a 
separate stack.

It's based on 2.6.12 'cos that's how out of date I am.  :-)

Maybe it'll be of use to someone.

Please CC john@calva.com with any comments, I'm not subscribed to the list.