rcutorture: Add test of RCU CPU stall notifiers

This commit registers an RCU CPU stall notifier when testing RCU CPU
stalls.  The notifier logs a message similar to the following:

	rcu_torture_stall_nf: v=1, duration=21001.

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