Re: [RFC][PATCH 02/21] tracing: Reimplement log2

Steven Rostedt
2017-02-08T20:15:14Z

On Wed, 8 Feb 2017 11:24:58 -0600
Tom Zanussi <tom.zanussi@linux.intel.com> wrote:

> static void destroy_hist_field(struct hist_field *hist_field)
> {
> + unsigned int i;
> +
> + if (!hist_field)
> + return;
> +
> + for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
> + destroy_hist_field(hist_field->operands[i]);

Recursive functions get me really nervous. What limits it? Is this user
defined? Perhaps we need to find a better way to handle this that's not
recursive, or at least put in a hard limit of the amount it can recurse.

-- Steve

> +
> kfree(hist_field);
> }
>
> @@ -377,7 +393,10 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
> }
>
> if (flags & HIST_FIELD_FL_LOG2) {
> + unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
> hist_field->fn = hist_field_log2;
> + hist_field->operands[0] = create_hist_field(field, fl);
> + hist_field->size = hist_field->operands[0]->size;
> goto out;
> }
>