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Subject[PATCH v7 10/16] tracing: Add hist trigger onchange() handler
Date
From: Tom Zanussi <tom.zanussi@linux.intel.com>

Add support for a hist:onchange($var) handler, similar to the onmax()
handler but triggering whenever there's any change in $var, not just a
max.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
---
kernel/trace/trace.c | 3 +-
kernel/trace/trace_events_hist.c | 68 ++++++++++++++++++++++++++++++++--------
2 files changed, 57 insertions(+), 14 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9b84d2f4227a..8eb5d6559ad3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4882,7 +4882,8 @@ static const char readme_msg[] =
"\t <handler>.<action>\n\n"
"\t The available handlers are:\n\n"
"\t onmatch(matching.event) - invoke on addition or update\n"
- "\t onmax(var) - invoke if var exceeds current max\n\n"
+ "\t onmax(var) - invoke if var exceeds current max\n"
+ "\t onchange(var) - invoke action if var changes\n\n"
"\t The available actions are:\n\n"
"\t <synthetic_event>(param list) - generate synthetic event\n"
"\t save(field,...) - save current event fields\n"
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 5e21d2ee71ed..f8f583ae2e54 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -331,6 +331,7 @@ typedef u64 (*get_track_val_fn_t) (struct hist_trigger_data *hist_data,
enum handler_id {
HANDLER_ONMATCH = 1,
HANDLER_ONMAX,
+ HANDLER_ONCHANGE,
};

enum action_id {
@@ -1906,7 +1907,8 @@ static int parse_action(char *str, struct hist_trigger_attrs *attrs)
return ret;

if ((strncmp(str, "onmatch(", strlen("onmatch(")) == 0) ||
- (strncmp(str, "onmax(", strlen("onmax(")) == 0)) {
+ (strncmp(str, "onmax(", strlen("onmax(")) == 0) ||
+ (strncmp(str, "onchange(", strlen("onchange(")) == 0)) {
attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
if (!attrs->action_str[attrs->n_actions]) {
ret = -ENOMEM;
@@ -3366,6 +3368,14 @@ static bool check_track_val_max(u64 track_val, u64 var_val)
return true;
}

+static bool check_track_val_changed(u64 track_val, u64 var_val)
+{
+ if (var_val == track_val)
+ return false;
+
+ return true;
+}
+
static u64 get_track_val_local(struct hist_trigger_data *hist_data,
struct tracing_map_elt *elt,
struct action_data *data)
@@ -3540,6 +3550,8 @@ static void track_data_print(struct seq_file *m,

if (data->handler == HANDLER_ONMAX)
seq_printf(m, "\n\tmax: %10llu", track_val);
+ else if (data->handler == HANDLER_ONCHANGE)
+ seq_printf(m, "\n\tchanged: %10llu", track_val);

if (data->action == ACTION_SNAPSHOT)
return;
@@ -3570,10 +3582,10 @@ static void ontrack_save(struct hist_trigger_data *hist_data,
update_save_vars(hist_data, elt, rbe, rec);
}

-static void onmax_snapshot(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)
+static void ontrack_snapshot(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)
{
update_track_val(hist_data, elt, data, var_ref_vals);
}
@@ -3634,14 +3646,14 @@ static int track_data_create(struct hist_trigger_data *hist_data,

track_data_var_str = data->track_data.var_str;
if (track_data_var_str[0] != '$') {
- hist_err("For onmax(x), x must be a variable: ", track_data_var_str);
+ hist_err("For onmax(x) or onchange(x), x must be a variable: ", track_data_var_str);
return -EINVAL;
}
track_data_var_str++;

var_field = find_target_event_var(hist_data, NULL, NULL, track_data_var_str);
if (!var_field) {
- hist_err("Couldn't find onmax variable: ", track_data_var_str);
+ hist_err("Couldn't find onmax or onchange variable: ", track_data_var_str);
return -EINVAL;
}

@@ -3668,6 +3680,14 @@ static int track_data_create(struct hist_trigger_data *hist_data,
ret = PTR_ERR(track_var);
goto out;
}
+
+ if (data->handler == HANDLER_ONCHANGE)
+ track_var = create_var(hist_data, file, "__change", sizeof(u64), "u64");
+ if (IS_ERR(track_var)) {
+ hist_err("Couldn't create onchange variable: ", "__change");
+ ret = PTR_ERR(track_var);
+ goto out;
+ }
data->track_data.track_var = track_var;

ret = action_create(hist_data, data);
@@ -3747,6 +3767,8 @@ static int action_parse(char *str, struct action_data *data,

if (handler == HANDLER_ONMAX)
data->track_data.check_val = check_track_val_max;
+ else if (handler == HANDLER_ONCHANGE)
+ data->track_data.check_val = check_track_val_changed;
else {
hist_err("action parsing: Handler doesn't support action: ", action_name);
ret = -EINVAL;
@@ -3770,6 +3792,8 @@ static int action_parse(char *str, struct action_data *data,

if (handler == HANDLER_ONMAX)
data->track_data.check_val = check_track_val_max;
+ else if (handler == HANDLER_ONCHANGE)
+ data->track_data.check_val = check_track_val_changed;
else {
hist_err("action parsing: Handler doesn't support action: ", action_name);
ret = -EINVAL;
@@ -3779,7 +3803,7 @@ static int action_parse(char *str, struct action_data *data,
data->track_data.save_val = save_track_val_snapshot;
data->track_data.get_val = get_track_val_snapshot;

- data->fn = onmax_snapshot;
+ data->fn = ontrack_snapshot;

data->action = ACTION_SNAPSHOT;
} else {
@@ -3793,6 +3817,8 @@ static int action_parse(char *str, struct action_data *data,

if (handler == HANDLER_ONMAX)
data->track_data.check_val = check_track_val_max;
+ else if (handler == HANDLER_ONCHANGE)
+ data->track_data.check_val = check_track_val_changed;

data->track_data.save_val = save_track_val_local;
data->track_data.get_val = get_track_val_local;
@@ -4654,7 +4680,8 @@ static void destroy_actions(struct hist_trigger_data *hist_data)

if (data->handler == HANDLER_ONMATCH)
onmatch_destroy(data);
- else if (data->handler == HANDLER_ONMAX)
+ else if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE)
track_data_destroy(hist_data, data);
else
kfree(data);
@@ -4689,6 +4716,15 @@ static int parse_actions(struct hist_trigger_data *hist_data)
ret = PTR_ERR(data);
break;
}
+ } else if (strncmp(str, "onchange(", strlen("onchange(")) == 0) {
+ char *action_str = str + strlen("onchange(");
+
+ data = track_data_parse(hist_data, action_str,
+ HANDLER_ONCHANGE);
+ if (IS_ERR(data)) {
+ ret = PTR_ERR(data);
+ break;
+ }
} else {
ret = -EINVAL;
break;
@@ -4713,7 +4749,8 @@ static int create_actions(struct hist_trigger_data *hist_data)
ret = onmatch_create(hist_data, data);
if (ret)
break;
- } else if (data->handler == HANDLER_ONMAX) {
+ } else if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE) {
ret = track_data_create(hist_data, data);
if (ret)
break;
@@ -4741,7 +4778,8 @@ static void print_actions(struct seq_file *m,
continue;
}

- if (data->handler == HANDLER_ONMAX)
+ if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE)
track_data_print(m, hist_data, elt, data);
}
}
@@ -4773,6 +4811,8 @@ static void print_track_data_spec(struct seq_file *m,
{
if (data->handler == HANDLER_ONMAX)
seq_puts(m, ":onmax(");
+ else if (data->handler == HANDLER_ONCHANGE)
+ seq_puts(m, ":onchange(");
seq_printf(m, "%s", data->track_data.var_str);
seq_printf(m, ").%s(", data->action_name);

@@ -4830,7 +4870,8 @@ static bool actions_match(struct hist_trigger_data *hist_data,
if (strcmp(data->match_data.event,
data_test->match_data.event) != 0)
return false;
- } else if (data->handler == HANDLER_ONMAX) {
+ } else if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE) {
if (strcmp(data->track_data.var_str,
data_test->track_data.var_str) != 0)
return false;
@@ -4851,7 +4892,8 @@ static void print_actions_spec(struct seq_file *m,

if (data->handler == HANDLER_ONMATCH)
print_onmatch_spec(m, hist_data, data);
- else if (data->handler == HANDLER_ONMAX)
+ else if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE)
print_track_data_spec(m, hist_data, data);
}
}
--
2.14.1
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