rcutorture: Limit read-side polling-API testing

RCU's polled grace-period API is reasonably lightweight, but still
contains heavyweight memory barriers.  This commit therefore limits
testing of this API from rcutorture's readers in order to avoid the
false negatives that these heavyweight operations could provoke.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
1 file changed