Re: [RFC][PATCH 01/21] tracing: Add hist_field_name() accessor

Steven Rostedt
2017-02-08T20:09:17Z

On Wed, 8 Feb 2017 11:24:57 -0600
Tom Zanussi <tom.zanussi@linux.intel.com> wrote:

> In preparation for hist_fields that won't be strictly based on
> trace_event_fields, add a new hist_field_name() accessor to allow that
> flexibility and update associated users.
>
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
> kernel/trace/trace_events_hist.c | 59 +++++++++++++++++++++++++---------------
> 1 file changed, 37 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index f3a960e..37347d7 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -145,6 +145,16 @@ struct hist_trigger_data {
> struct tracing_map *map;
> };
>
> +static const char *hist_field_name(struct hist_field *field)
> +{
> + const char *field_name = NULL;
> +
> + if (field->field)
> + field_name = field->field->name;
> +
> + return field_name;
> +}

It would be much simpler to do:

{
if (field->field)
return field->field->name;

return NULL;
}

or even:

return field->field ? field->field->name : NULL;

> +
> static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)
> {
> hist_field_fn_t fn = NULL;
> @@ -652,7 +662,6 @@ static int is_descending(const char *str)
> static int create_sort_keys(struct hist_trigger_data *hist_data)
> {
> char *fields_str = hist_data->attrs->sort_key_str;
> - struct ftrace_event_field *field = NULL;
> struct tracing_map_sort_key *sort_key;
> int descending, ret = 0;
> unsigned int i, j;
> @@ -669,7 +678,9 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
> }
>
> for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
> + struct hist_field *hist_field;
> char *field_str, *field_name;
> + const char *test_name;
>
> sort_key = &hist_data->sort_keys[i];
>
> @@ -702,8 +713,9 @@ static int create_sort_keys(struct hist_trigger_data *hist_data)
> }
>
> for (j = 1; j < hist_data->n_fields; j++) {
> - field = hist_data->fields[j]->field;
> - if (field && (strcmp(field_name, field->name) == 0)) {
> + hist_field = hist_data->fields[j];
> + test_name = hist_field_name(hist_field);
> + if (strcmp(field_name, test_name) == 0) {

If hist_field_name() returns NULL, the strcmp() will crash.

> sort_key->field_idx = j;
> descending = is_descending(field_str);
> if (descending < 0) {
> @@ -951,6 +963,7 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
> struct hist_field *key_field;
> char str[KSYM_SYMBOL_LEN];
> bool multiline = false;
> + const char *field_name;
> unsigned int i;
> u64 uval;
>

-- Steve