linux-kernel - Re: [PATCH v3 2/3] tracing: Add trace

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Date:   Wed, 31 Aug 2016 11:35:40 +0530
From:   Binoy Jayan <binoy.jayan@...aro.org>
To:     Daniel Wagner <daniel.wagner@...-carit.de>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        linaro-kernel@...ts.linaro.org, Carsten Emde <C.Emde@...dl.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>,
        Masami <masami.hiramatsu@...aro.org>
Subject: Re: [PATCH v3 2/3] tracing: Add trace_irqsoff tracepoints

Hi Daniel/Steven,

On 30 August 2016 at 20:32, Daniel Wagner <daniel.wagner@...-carit.de> wrote:
> On 08/30/2016 04:20 PM, Daniel Wagner wrote:
>> Just setting the size of the type is not enough. The hist_field_*
>> getter function want to know the offset too:
>
> With this hack here it should work. The COMM generic field is handled via
> the tracing_map_ops. We could do it also there but than we need to
> a condition in the trace_map_ops if it is COMM or CPU.
> This shortcut here avoids it:

> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index f3a960e..77073b7 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -556,6 +567,11 @@ static int create_key_field(struct hist_trigger_data *hist_data,
>                         key_size = MAX_FILTER_STR_VAL;
>                 else
>                         key_size = field->size;
> +
> +               // strcmp(field_name, "cpu") would also work to figure
> +               // out if this is a one of the generic fields.
> +               if (field->filter_type == FILTER_CPU)
> +                       flags |= HIST_FIELD_FL_CPU;
>         }
>
>         hist_data->fields[key_idx] = create_hist_field(field, flags);

I applied Daniel's fix and it seems to work. Can we use the following instead
on top of your patch? Like how the other keys are compared against
respective fields?

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 46203b7..963a121 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -537,6 +537,12 @@ static int create_key_field(struct
hist_trigger_data *hist_data,
  } else {
  char *field_name = strsep(&field_str, ".");

+                /* Cannot keep these 2 lines in side the if() below
+                 * as field_str would be NULL for the key 'cpu'
+                 */
+                if (strcmp(field_name, "cpu") == 0)
+                        flags |= HIST_FIELD_FL_CPU;
+
  if (field_str) {
  if (strcmp(field_str, "hex") == 0)
  flags |= HIST_FIELD_FL_HEX;
@@ -568,11 +574,6 @@ static int create_key_field(struct
hist_trigger_data *hist_data,
  else
  key_size = field->size;

- // strcmp(field_name, "cpu") would also work to figure
- // out if this is a one of the generic fields.
- if (field->filter_type == FILTER_CPU)
- flags |= HIST_FIELD_FL_CPU;
-
  }

  hist_data->fields[key_idx] = create_hist_field(field, flags);

- Binoy