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Subject[PATCH v15 08/15] 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 | 58 ++++++++++++++++++++++++++++++++++------
2 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index afcf8100a6b3..76742db70ba0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4915,7 +4915,8 @@ 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 7f2d420ebb35..f9eee15877b7 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -391,6 +391,7 @@ typedef bool (*check_track_val_fn_t) (u64 track_val, u64 var_val);
enum handler_id {
HANDLER_ONMATCH = 1,
HANDLER_ONMAX,
+ HANDLER_ONCHANGE,
};

enum action_id {
@@ -1989,7 +1990,8 @@ static int parse_action(char *str, struct hist_trigger_attrs *attrs)
return ret;

if ((str_has_prefix(str, "onmatch(")) ||
- (str_has_prefix(str, "onmax("))) {
+ (str_has_prefix(str, "onmax(")) ||
+ (str_has_prefix(str, "onchange("))) {
attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
if (!attrs->action_str[attrs->n_actions]) {
ret = -ENOMEM;
@@ -3481,6 +3483,14 @@ 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(struct hist_trigger_data *hist_data,
struct tracing_map_elt *elt,
struct action_data *data)
@@ -3640,6 +3650,8 @@ 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;
@@ -3727,14 +3739,14 @@ 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;
}

@@ -3751,6 +3763,14 @@ 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);
@@ -3830,6 +3850,8 @@ 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;
@@ -3850,6 +3872,8 @@ 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;
@@ -3870,6 +3894,8 @@ 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;

if (handler != HANDLER_ONMATCH) {
data->track_data.save_data = action_trace;
@@ -4700,7 +4726,8 @@ 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);
@@ -4736,6 +4763,15 @@ static int parse_actions(struct hist_trigger_data *hist_data)
ret = PTR_ERR(data);
break;
}
+ } else if ((len = str_has_prefix(str, "onchange("))) {
+ char *action_str = str + len;
+
+ data = track_data_parse(hist_data, action_str,
+ HANDLER_ONCHANGE);
+ if (IS_ERR(data)) {
+ ret = PTR_ERR(data);
+ break;
+ }
} else {
ret = -EINVAL;
break;
@@ -4760,7 +4796,8 @@ 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;
@@ -4785,7 +4822,8 @@ static void print_actions(struct seq_file *m,
if (data->action == ACTION_SNAPSHOT)
continue;

- if (data->handler == HANDLER_ONMAX)
+ if (data->handler == HANDLER_ONMAX ||
+ data->handler == HANDLER_ONCHANGE)
track_data_print(m, hist_data, elt, data);
}
}
@@ -4817,6 +4855,8 @@ 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);

@@ -4874,7 +4914,8 @@ 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;
@@ -4895,7 +4936,8 @@ 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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