tracing: Add a per-event-trigger 'paused' field

Add a simple per-trigger 'paused' flag, allowing individual triggers
to pause.  We could leave it to individual triggers that need this
functionality to do it themselves, but we also want to allow other
events to control pausing, so add it to the trigger data.

Link: http://lkml.kernel.org/r/fed37e4879684d7dcc57fe00ce0cbf170032b06d.1449767187.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.h

@@ -1172,6 +1172,7 @@ struct event_trigger_data {
 	struct event_filter __rcu	*filter;
 	char				*filter_str;
 	void				*private_data;
+	bool				paused;
 	struct list_head		list;
 };
 

kernel/trace/trace_events_trigger.c

@@ -72,6 +72,8 @@ event_triggers_call(struct trace_event_file *file, void *rec)
 		return tt;
 
 	list_for_each_entry_rcu(data, &file->triggers, list) {
+		if (data->paused)
+			continue;
 		if (!rec) {
 			data->ops->func(data, rec);
 			continue;
@@ -110,6 +112,8 @@ event_triggers_post_call(struct trace_event_file *file,
 	struct event_trigger_data *data;
 
 	list_for_each_entry_rcu(data, &file->triggers, list) {
+		if (data->paused)
+			continue;
 		if (data->cmd_ops->trigger_type & tt)
 			data->ops->func(data, rec);
 	}