iommu_alloc failure and panic

[Anton Blanchard]

Hi,

> It looks like they are already on:
> 
> CONFIG_DEBUG_STACKOVERFLOW=y
> CONFIG_DEBUG_STACK_USAGE=y

You could try bumping the limit for the warning in
arch/powerpc/kernel/irq.c

	if (unlikely(sp < (sizeof(struct thread_info) + 2048)))

Change it to 4096.

Unfortunately if the long call chain is in an interrupt disabled area
you will not get warned.

> The machine is frozen after the panic. 

You can do it sometime before the hang to see if you are getting close
to overflowing the stack.

Anton