Date: Wed, 2 Mar 2016 12:39:31 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: masami.hiramatsu.pt@hitachi.com, namhyung@kernel.org,
        josh@joshtriplett.org, andi@firstfloor.org,
        mathieu.desnoyers@efficios.com, peterz@infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v15 10/23] tracing: Add hist trigger 'execname' modifier
Message-ID: <20160302123931.37f28d4a@gandalf.local.home>
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	<733e60a8acc79f777502cbe6c98d5abd2c33a17e.1456501855.git.tom.zanussi@linux.intel.com>
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On Fri, 26 Feb 2016 10:01:13 -0600
Tom Zanussi <tom.zanussi@linux.intel.com> wrote:


> +static void hist_trigger_elt_copy(struct tracing_map_elt *to,
> +				  struct tracing_map_elt *from)
> +{
> +	char *comm_from = from->private_data;
> +	char *comm_to = to->private_data;
> +
> +	if (comm_from)
> +		memcpy(comm_to, comm_from, TASK_COMM_LEN + 1);
> +}
> +
> +static void hist_trigger_elt_init(struct tracing_map_elt *elt)
> +{
> +	char *comm = elt->private_data;
> +
> +	if (comm)
> +		save_comm(comm, current);
> +}
> +
> +static const struct tracing_map_ops hist_trigger_ops = {
> +	.elt_alloc	= hist_trigger_elt_alloc,
> +	.elt_copy	= hist_trigger_elt_copy,
> +	.elt_free	= hist_trigger_elt_free,
> +	.elt_init	= hist_trigger_elt_init,

These are only used for saving or displaying comm. Wouldn't adding that
in the name be better. Otherwise it looks like they are more generic. I
find that dangerous, especially since they just assume that the
private_data is a string.

What about hist_trigger_elt_comm_*

?

-- Steve

> +};
> +
>  static void destroy_hist_field(struct hist_field *hist_field)
>  {
>  	kfree(hist_field);
> @@ -399,6 +467,9 @@ static int create_key_field(struct hist_trigger_data *hist_data,
>  			flags |= HIST_FIELD_FL_SYM;
>  		else if (strcmp(field_str, "sym-offset") == 0)
>  			flags |= HIST_FIELD_FL_SYM_OFFSET;
> +		else if ((strcmp(field_str, "execname") == 0) &&
> +			 (strcmp(field_name, "common_pid") == 0))
> +			flags |= HIST_FIELD_FL_EXECNAME;
>  		else {
>  			ret = -EINVAL;
>  			goto out;