From: Tom Zanussi <tom.zanussi@linux.intel.com>
Date: Mon, 26 Jun 2017 17:49:22 -0500
Subject: tracing: Add hist trigger action hook
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 8624ffe346cb0f710fefb20cb228b5d8eaab860e
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

Add a hook for executing extra actions whenever a histogram entry is
added or updated.

The default 'action' when a hist entry is added to a histogram is to
update the set of values associated with it.  Some applications may
want to perform additional actions at that point, such as generate
another event, or compare and save a maximum.

Add a simple framework for doing that; specific actions will be
implemented on top of it in later patches.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 kernel/trace/trace_events_hist.c |  114 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 111 insertions(+), 3 deletions(-)

--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -33,6 +33,7 @@ typedef u64 (*hist_field_fn_t) (struct h
 
 #define HIST_FIELD_OPERANDS_MAX	2
 #define HIST_FIELDS_MAX		(TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
+#define HIST_ACTIONS_MAX	8
 
 enum field_op_id {
 	FIELD_OP_NONE,
@@ -233,6 +234,9 @@ struct hist_trigger_attrs {
 
 	char		*assignment_str[TRACING_MAP_VARS_MAX];
 	unsigned int	n_assignments;
+
+	char		*action_str[HIST_ACTIONS_MAX];
+	unsigned int	n_actions;
 };
 
 struct hist_trigger_data {
@@ -252,6 +256,21 @@ struct hist_trigger_data {
 	bool				remove;
 	struct hist_field               *var_refs[TRACING_MAP_VARS_MAX];
 	unsigned int			n_var_refs;
+
+	struct action_data		*actions[HIST_ACTIONS_MAX];
+	unsigned int			n_actions;
+};
+
+struct action_data;
+
+typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
+			     struct tracing_map_elt *elt, void *rec,
+			     struct ring_buffer_event *rbe,
+			     struct action_data *data, u64 *var_ref_vals);
+
+struct action_data {
+	action_fn_t		fn;
+	unsigned int		var_ref_idx;
 };
 
 static u64 hist_field_timestamp(struct hist_field *hist_field,
@@ -681,6 +700,9 @@ static void destroy_hist_trigger_attrs(s
 	for (i = 0; i < attrs->n_assignments; i++)
 		kfree(attrs->assignment_str[i]);
 
+	for (i = 0; i < attrs->n_actions; i++)
+		kfree(attrs->action_str[i]);
+
 	kfree(attrs->name);
 	kfree(attrs->sort_key_str);
 	kfree(attrs->keys_str);
@@ -688,6 +710,16 @@ static void destroy_hist_trigger_attrs(s
 	kfree(attrs);
 }
 
+static int parse_action(char *str, struct hist_trigger_attrs *attrs)
+{
+	int ret = 0;
+
+	if (attrs->n_actions >= HIST_ACTIONS_MAX)
+		return ret;
+
+	return ret;
+}
+
 static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
 {
 	int ret = 0;
@@ -755,8 +787,9 @@ static struct hist_trigger_attrs *parse_
 		else if (strcmp(str, "clear") == 0)
 			attrs->clear = true;
 		else {
-			ret = -EINVAL;
-			goto free;
+			ret = parse_action(str, attrs);
+			if (ret)
+				goto free;
 		}
 	}
 
@@ -1722,11 +1755,63 @@ static int create_sort_keys(struct hist_
 	return ret;
 }
 
+static void destroy_actions(struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+
+		kfree(data);
+	}
+}
+
+static int create_actions(struct hist_trigger_data *hist_data,
+			  struct trace_event_file *file)
+{
+	unsigned int i;
+	int ret = 0;
+	char *str;
+
+	for (i = 0; i < hist_data->attrs->n_actions; i++) {
+		str = hist_data->attrs->action_str[i];
+	}
+
+	return ret;
+}
+
+static void print_actions(struct seq_file *m,
+			  struct hist_trigger_data *hist_data,
+			  struct tracing_map_elt *elt)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+	}
+}
+
+static void print_actions_spec(struct seq_file *m,
+			       struct hist_trigger_data *hist_data)
+{
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		struct action_data *data = hist_data->actions[i];
+	}
+}
+
 static void destroy_hist_data(struct hist_trigger_data *hist_data)
 {
+	if (!hist_data)
+		return;
+
 	destroy_hist_trigger_attrs(hist_data->attrs);
 	destroy_hist_fields(hist_data);
 	tracing_map_destroy(hist_data->map);
+
+	destroy_actions(hist_data);
+
 	kfree(hist_data);
 }
 
@@ -1887,6 +1972,20 @@ static inline void add_to_key(char *comp
 		memcpy(compound_key + key_field->offset, key, size);
 }
 
+static void
+hist_trigger_actions(struct hist_trigger_data *hist_data,
+		     struct tracing_map_elt *elt, void *rec,
+		     struct ring_buffer_event *rbe, u64 *var_ref_vals)
+{
+	struct action_data *data;
+	unsigned int i;
+
+	for (i = 0; i < hist_data->n_actions; i++) {
+		data = hist_data->actions[i];
+		data->fn(hist_data, elt, rec, rbe, data, var_ref_vals);
+	}
+}
+
 static void event_hist_trigger(struct event_trigger_data *data, void *rec,
 			       struct ring_buffer_event *rbe)
 {
@@ -1942,6 +2041,9 @@ static void event_hist_trigger(struct ev
 		return;
 
 	hist_trigger_elt_update(hist_data, elt, rec, rbe, var_ref_vals);
+
+	if (resolve_var_refs(hist_data, key, var_ref_vals, true))
+		hist_trigger_actions(hist_data, elt, rec, rbe, var_ref_vals);
 }
 
 static void hist_trigger_stacktrace_print(struct seq_file *m,
@@ -2279,6 +2381,8 @@ static int event_hist_trigger_print(stru
 	}
 	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
 
+	print_actions_spec(m, hist_data);
+
 	if (data->filter_str)
 		seq_printf(m, " if %s", data->filter_str);
 
@@ -2741,6 +2845,10 @@ static int event_hist_trigger_func(struc
 	if (has_hist_vars(hist_data))
 		save_hist_vars(hist_data);
 
+	ret = create_actions(hist_data, file);
+	if (ret)
+		goto out_unreg;
+
 	ret = tracing_map_init(hist_data->map);
 	if (ret)
 		goto out_unreg;
@@ -2762,8 +2870,8 @@ enable:
 	remove_hist_vars(hist_data);
 
 	kfree(trigger_data);
-
 	destroy_hist_data(hist_data);
+
 	goto out;
 }