debug problems on ppc 83xx target due to changed struct task_struct

[Dave Hansen]

On 08/12/2016 07:50 AM, Holger Brunck wrote:
> When I try to debug our multithreaded userspace application with gdb I  get
> stuck when trying to single step code.

Can you clarify "stuck"?  Like the instructions don't advance?  Have you
been able to find a root cause for this?

> Does anyone have an idea why the change in sched.h break my debug
> usecase? Anyone out here who is debugging ppc83xx targets flawlessly
> with a recent kernel?

Thanks for going to the trouble of bisecting this, btw!

I'd _suspect_ something very specific to your platform since this
doesn't appear to affect even other ppc variants.

I wonder if making it cross a page boundary from some other structure
causes this, or moving it relative to something else.  Could you try
moving it to a few more places, or padding it by, say PAGE_SIZE on
either side makes a difference?

Is there some assembly involved in your single-stepping, or some other
code that assumes relative offsets between two pieces of 'task_struct'?