RCU list iterators: should prefetch ever be optimised out with no
side-effects, the current version will lose the barrier completely.
Pointed-out-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>