With physical CPU hotplug, the CPU is hot removed and it should not receive
any interrupts.  Disabling interrupt is much safer.  This basically is what we
do in ia64 & x86.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>