From: Pavel Machek <pavel@ucw.cz>

Its very bad idea to freeze migration threads, as it crashes machine upon
next call to "schedule()".  In refrigerator, I had one "wake_up_process()"
too many.  This fixes it.
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>