linux-kernel - Re: [PATCH v15 10/23] tracing: Add hist trigger 'execname' modifier

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Date:	Wed, 02 Mar 2016 13:51:57 -0600
From:	Tom Zanussi <tom.zanussi@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	masami.hiramatsu.pt@...achi.com, namhyung@...nel.org,
	josh@...htriplett.org, andi@...stfloor.org,
	mathieu.desnoyers@...icios.com, peterz@...radead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v15 10/23] tracing: Add hist trigger 'execname' modifier

Hi Steve,

On Wed, 2016-03-02 at 12:39 -0500, Steven Rostedt wrote:
> On Fri, 26 Feb 2016 10:01:13 -0600
> Tom Zanussi <tom.zanussi@...ux.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_*
> 
> ?

Yeah, I think that makes it clearer - I'll rename those to be more
explicit.

Thanks,

Tom

> 
> -- 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;