From: Paul Jackson <pj@sgi.com>

This patch makes cpu_present_map a real map for all configurations, instead of
a constant for non-SMP.  It also moves the definition of cpu_present_map out
of kernel/cpu.c into kernel/sched.c, because cpu.c isn't compiled into non-SMP
kernels.

The pattern is that each of the possible, present and online cpu maps are
actual kernel global cpumask_t variables, for all configurations.  They are
documented in include/linux/cpumask.h.  Some of the UP (NR_CPUS=1) code
cheats, and hardcodes the assumption that the single bit position of these
maps is always set, as an optimization.
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>