tracing: Add hist trigger onchange() handler

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.

Link: http://lkml.kernel.org/r/dfbc7e4ada242603e9ec3f049b5ad076a07dfd03.1550100284.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dd60c14..be6779f 100644 (file)
--- 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 571937a..2f3323c 100644 (file)
--- 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);
        }
 }