sparc64 prom_callback and new_setup_frame32 each operates on a user page
table without holding lock, and no doubt they've good reason.  But I'd
feel more confident if they were to do a "pte = *ptep" and then operate
on pte, rather than re-evaluating *ptep.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>