tracing: Add enable_hist/disable_hist triggers

Similar to enable_event/disable_event triggers, these triggers enable
and disable the aggregation of events into maps rather than enabling
and disabling their writing into the trace buffer.

They can be used to automatically start and stop hist triggers based
on a matching filter condition.

If there's a paused hist trigger on system:event, the following would
start it when the filter condition was hit:

  # echo enable_hist:system:event [ if filter] > event/trigger

And the following would disable a running system:event hist trigger:

  # echo disable_hist:system:event [ if filter] > event/trigger

See Documentation/trace/events.txt for real examples.

Link: http://lkml.kernel.org/r/f812f086e52c8b7c8ad5443487375e03c96a601f.1457029949.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>

1 files changed, 115 insertions, 0 deletions

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 4f4041d76926..5d4f02792440 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1393,3 +1393,118 @@ __init int register_trigger_hist_cmd(void)
 
 	return ret;
 }
+
+static void
+hist_enable_trigger(struct event_trigger_data *data, void *rec)
+{
+	struct enable_trigger_data *enable_data = data->private_data;
+	struct event_trigger_data *test;
+
+	list_for_each_entry_rcu(test, &enable_data->file->triggers, list) {
+		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			if (enable_data->enable)
+				test->paused = false;
+			else
+				test->paused = true;
+			break;
+		}
+	}
+}
+
+static void
+hist_enable_count_trigger(struct event_trigger_data *data, void *rec)
+{
+	if (!data->count)
+		return;
+
+	if (data->count != -1)
+		(data->count)--;
+
+	hist_enable_trigger(data, rec);
+}
+
+static struct event_trigger_ops hist_enable_trigger_ops = {
+	.func			= hist_enable_trigger,
+	.print			= event_enable_trigger_print,
+	.init			= event_trigger_init,
+	.free			= event_enable_trigger_free,
+};
+
+static struct event_trigger_ops hist_enable_count_trigger_ops = {
+	.func			= hist_enable_count_trigger,
+	.print			= event_enable_trigger_print,
+	.init			= event_trigger_init,
+	.free			= event_enable_trigger_free,
+};
+
+static struct event_trigger_ops hist_disable_trigger_ops = {
+	.func			= hist_enable_trigger,
+	.print			= event_enable_trigger_print,
+	.init			= event_trigger_init,
+	.free			= event_enable_trigger_free,
+};
+
+static struct event_trigger_ops hist_disable_count_trigger_ops = {
+	.func			= hist_enable_count_trigger,
+	.print			= event_enable_trigger_print,
+	.init			= event_trigger_init,
+	.free			= event_enable_trigger_free,
+};
+
+static struct event_trigger_ops *
+hist_enable_get_trigger_ops(char *cmd, char *param)
+{
+	struct event_trigger_ops *ops;
+	bool enable;
+
+	enable = (strcmp(cmd, ENABLE_HIST_STR) == 0);
+
+	if (enable)
+		ops = param ? &hist_enable_count_trigger_ops :
+			&hist_enable_trigger_ops;
+	else
+		ops = param ? &hist_disable_count_trigger_ops :
+			&hist_disable_trigger_ops;
+
+	return ops;
+}
+
+static struct event_command trigger_hist_enable_cmd = {
+	.name			= ENABLE_HIST_STR,
+	.trigger_type		= ETT_HIST_ENABLE,
+	.func			= event_enable_trigger_func,
+	.reg			= event_enable_register_trigger,
+	.unreg			= event_enable_unregister_trigger,
+	.get_trigger_ops	= hist_enable_get_trigger_ops,
+	.set_filter		= set_trigger_filter,
+};
+
+static struct event_command trigger_hist_disable_cmd = {
+	.name			= DISABLE_HIST_STR,
+	.trigger_type		= ETT_HIST_ENABLE,
+	.func			= event_enable_trigger_func,
+	.reg			= event_enable_register_trigger,
+	.unreg			= event_enable_unregister_trigger,
+	.get_trigger_ops	= hist_enable_get_trigger_ops,
+	.set_filter		= set_trigger_filter,
+};
+
+static __init void unregister_trigger_hist_enable_disable_cmds(void)
+{
+	unregister_event_command(&trigger_hist_enable_cmd);
+	unregister_event_command(&trigger_hist_disable_cmd);
+}
+
+__init int register_trigger_hist_enable_disable_cmds(void)
+{
+	int ret;
+
+	ret = register_event_command(&trigger_hist_enable_cmd);
+	if (WARN_ON(ret < 0))
+		return ret;
+	ret = register_event_command(&trigger_hist_disable_cmd);
+	if (WARN_ON(ret < 0))
+		unregister_trigger_hist_enable_disable_cmds();
+
+	return ret;
+}