[Not upstream in the same way, as it was fixed differently there]

6f6198a7 sched: kill migration thread in CPU_POST_DEAD instead of CPU_DEAD
leaves migration threads lying about.  Mask out CPU_TASKS_FROZEN.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>