Back in early 2008, 4KiB stack support was added to reduce memory
consumption on workloads with lots of threads, using a separate IRQ
stack per CPU to alleviate stack pressure. However the SMP code added a
year and a half later didn't set up the IRQ stack when bringing up
secondary CPUs, resulting
A couple of patches I've applied for v4.4 relating to 4KB stack support
with SMP. Basically 4KB stacks never quite worked with SMP since the IRQ
stack was never set up on secondary threads. This causes boot failure if
enabled accidentally.
The first patch sets up and tears down the IRQ stack
