tracing: Fix synchronizing to event changes with tracepoint_synchronize_unregister()

Now that some trace events can be protected by srcu_read_lock(tracepoint_srcu),
we need to make sure all locations that depend on this are also protected.
There were many places that did a synchronize_sched() thinking that it was
enough to protect againts access to trace events. This use to be the case,
but now that we use SRCU for _rcuidle() trace events, they may not be
protected by synchronize_sched(), as they may be called in paths that RCU is
not watching for preempt disable.

Fixes: e6753f23d9 ("tracepoint: Make rcuidle tracepoint callers use SRCU")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_events_hist.c

@@ -5141,7 +5141,7 @@ static void hist_clear(struct event_trigger_data *data)
 	if (data->name)
 		pause_named_trigger(data);
 
-	synchronize_sched();
+	tracepoint_synchronize_unregister();
 
 	tracing_map_clear(hist_data->map);