Re: [PATCH 18/32] tracing: Add simple expression support to hist triggers

Tom Zanussi
2017-07-21T16:29:23Z

Hi Namhyung,

On Fri, 2017-07-21 at 11:02 +0900, Namhyung Kim wrote:
> Hi Tom,
>
> On Mon, Jun 26, 2017 at 05:49:19PM -0500, Tom Zanussi wrote:
> > Add support for simple addition, subtraction, and unary expressions
> > (-(expr) and expr, where expr = b-a, a+b, a+b+c) to hist triggers, in
> > order to support a minimal set of useful inter-event calculations.
> >
> > These operations are needed for calculating latencies between events
> > (timestamp1-timestamp0) and for combined latencies (latencies over 3
> > or more events).
> >
> > In the process, factor out some common code from key and value
> > parsing.
> >
> > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> > ---
>
> [SNIP]
> > +static char *expr_str(struct hist_field *field, unsigned int level)
> > +{
> > + char *expr = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
> > +
> > + if (!expr || level > 1)
> > + return NULL;
>
> Looks like a memory leak.
>
>

Indeed, and so obvious I can't believe I missed it. Thanks for pointing
it out.

> [SNIP]
> > +static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
> > + struct trace_event_file *file,
> > + char *str, unsigned long flags,
> > + char *var_name, unsigned int level)
> > +{
> > + struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
> > + unsigned long operand_flags;
> > + int field_op, ret = -EINVAL;
> > + char *sep, *operand1_str;
> > +
> > + if (level > 2)
> > + return NULL;
> > +
> > + field_op = contains_operator(str);
> > + if (field_op == FIELD_OP_NONE)
> > + return NULL;
>
> Why not calling parse_atom() here? It'd make the code simpler IMHO.
>

Yeah, I think that would be much nicer, will do.

Thanks,

Tom