I've resynced Ben's patch against 2.5.40.  However, I'm getting some 
strange failures.  The patch is good enough to pass LTP, but 
consistently freezes when I run tcpdump on it.

Although I don't have CONFIG_PREEMPT on, I have the feeling that I 
need to disable preemption in common_interrupt() like it was before. 
   Any insights would be appreciated.

part of Ben LaHaise's original message:
 > Below is a patch against 2.5.20 that implements 4KB stacks for
 > tasks, plus a seperate 4KB irq stack for use by interrupts.  There
 > are a couple of reasons for doing this: 4KB stacks put less pressure
 > on the VM subsystem, reduces the overall memory usage for systems
 > with large numbers of tasks, and increases the reliability of the
 > system when under heavy irq load by provide a fixed stack size for
 > interrupt handlers that other kernel code will not eat into.
 >
 > The interrupt stacks are stackable, so we could use multiple
 > 4KB irq stacks.  The thread_info structure is included in each
 > interrupt stack, and has the current pointer copied into it upon
 > entry.

-- 
Dave Hansen
haveblue@us.ibm.com