This patch addresses some problems with wake_idle().  Currently wake_idle()
will wake a task on an alternate cpu if:

1) task->cpu is not idle
2) an idle cpu can be found

However the span of cpus to look for is very limited (only the task->cpu's
sibling).  The scheduler should find the closest idle cpu, starting with
the lowest level domain, then going to higher level domains if allowed
(doamin has flag SD_WAKE_IDLE).  This patch does this.

This and the other two patches (also to be submitted) combined have
provided as much at 5% improvement on that "online transaction DB workload"
and 2% on the industry standard J@EE workload.

I asked Martin Bligh to test these for regression, and he did not find any.
 I would like to submit for inclusion to -mm and barring any problems
eventually to mainline.

Signed-off-by: <habanero@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>