gather_stats() is called with a spinlock held from check_pte_range.  We
cannot reschedule with a lock held.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>