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    Subject[for-next][PATCH 21/29] tracing: Add hist trigger onchange() handler
    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.

    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>
    ---
    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 dd60c14a0fb0..be6779f963c6 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 571937a268a3..2f3323ca9d24 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);
    }
    }
    --
    2.20.1

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