Allow stack tracing to work when sampling on timer is forced using the
timer=1 boot option.  Reported by Akinobu Mita.
Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>