kernel/fork.c contains a disabled cache for task stuctures. task 
structures are placed into the task cache only if "tsk==current", and 
"tsk==current" is impossible. There is even a WARN_ON against that in 
__put_task_struct().

What should we do with it? I would remove it entirely - it's dead code. 
Any objections?

One problem is that order-1 allocations are not cached per-cpu - what 
about using kmem_cache_alloc for the stack?

--
    Manfred