tracepoint: Remove smp_read_barrier_depends() from comment

The comment in tracepoint_add_func() mentions smp_read_barrier_depends(),
whose use should be quite restricted.  This commit updates the comment
to instead mention the smp_store_release() and rcu_dereference_sched()
that the current code actually uses.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com>

kernel/tracepoint.c

@@ -212,11 +212,10 @@ static int tracepoint_add_func(struct tracepoint *tp,
 	}
 
 	/*
-	 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
-	 * probe callbacks array is consistent before setting a pointer to it.
-	 * This array is referenced by __DO_TRACE from
-	 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
-	 * is used.
+	 * rcu_assign_pointer has as smp_store_release() which makes sure
+	 * that the new probe callbacks array is consistent before setting
+	 * a pointer to it.  This array is referenced by __DO_TRACE from
+	 * include/linux/tracepoint.h using rcu_dereference_sched().
 	 */
 	rcu_assign_pointer(tp->funcs, tp_funcs);
 	if (!static_key_enabled(&tp->key))