rcu: Consolidate the RCU update functions invoked by sync.c

This commit retains all the various gp_ops[] entries, but makes their
update functions all be synchronize_rcu(), call_rcu() and rcu_barrier().
The read-side checks remain consistent with the various RCU flavors,
which still exist on the read side.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>

kernel/rcu/sync.c

@@ -44,15 +44,15 @@ static const struct {
 		__INIT_HELD(rcu_read_lock_held)
 	},
 	[RCU_SCHED_SYNC] = {
-		.sync = synchronize_sched,
-		.call = call_rcu_sched,
-		.wait = rcu_barrier_sched,
+		.sync = synchronize_rcu,
+		.call = call_rcu,
+		.wait = rcu_barrier,
 		__INIT_HELD(rcu_read_lock_sched_held)
 	},
 	[RCU_BH_SYNC] = {
-		.sync = synchronize_rcu_bh,
-		.call = call_rcu_bh,
-		.wait = rcu_barrier_bh,
+		.sync = synchronize_rcu,
+		.call = call_rcu,
+		.wait = rcu_barrier,
 		__INIT_HELD(rcu_read_lock_bh_held)
 	},
 };