U=y and start_secondary()
  is calling smp_callin() which in-turn calls synchronize_tsc_ap() which is
  of type __init. This should have meant broken CPU hotplug.

WARNING: vmlinux - Section mismatch: reference to .init.data: from .text between 'start_secondary' (at offset 0xc011603f) and 'initialize_secondary'
WARNING: vmlinux - Section mismatch: reference to .init.data: from .text between 'MP_processor_info' (at offset 0xc0116a4f) and 'mp_register_lapic'
WARNING: vmlinux - Section mismatch: reference to .init.data: from .text between 'MP_processor_info' (at offset 0xc0116a4f) and 'mp_register_lapic'

Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>