I was getting some pretty repeatable oopses while large numbers of
processes were exiting on my 16-way PIII while irqstacks, and 4k stacks
were turned on.  It is hard to trigger, and only happens when you're
using 4k stacks, not just irqstacks.

I traced it down to when smp_* interrupts were running.  It seems that
they use an interrupt entry path that doesn't include do_IRQ or
common_interrupt.  They use a BUILD_INTERRUPT macro, instead.  They were
blowing their 4k stacks when running softirqs.

So, what I did, was put the irqstack operations in a macro and call it
from common_interrupt, and the BUILD_INTERRUPT macros.  I also had to
change the calling conventions of the newly-affected handlers.

Ben, was there a reason that you didn't include these functions in your
original irqstack patches?  I always (wrongly) assumed that they were
really quick interrupts, and didn't use the stack heavily enough to be
worth modifying.

The a diff for the -mjb tree is attached.  I'll cook up another set of
vanilla ones tomorrow.

Does anybody want to see irqstacks as a config option?  These macros
would make it easier.
-- 
Dave Hansen
haveblue@us.ibm.com