From: Srivatsa Vaddagiri <vatsa@in.ibm.com>

Fix a CPU Hotplug problem wherein idle task's "->prio" value is not
restored to MAX_PRIO during CPU_DEAD handling.  Without this patch, once a
CPU is offlined and then later onlined, it becomes "more or less" useless
(does not run any task other than its idle task!)

Ingo said:

  The __setscheduler() call is (technically) incorrect because in the
  SCHED_NORMAL case the prio should be zero.  So it's a bit cleaner to set up
  the static priority to MAX_PRIO and then revert the policy to SCHED_NORMAL
  via __setscheduler().
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>