Re: [RFC PATCH v2 06/20] tracing/filters: Optimise scalar vs cpumask filtering when the user mask is a single CPU

Dan Carpenter
2023-07-31T16:03:23Z

On Mon, Jul 31, 2023 at 11:54:53AM -0400, Steven Rostedt wrote:
> On Mon, 31 Jul 2023 15:07:52 +0300
> Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> > On Sat, Jul 29, 2023 at 03:55:47PM -0400, Steven Rostedt wrote:
> > > > @@ -1761,6 +1761,11 @@ static int parse_pred(const char *str, void *data,
> > > > FILTER_PRED_FN_CPUMASK;
> > > > } else if (field->filter_type == FILTER_CPU) {
> > > > pred->fn_num = FILTER_PRED_FN_CPU_CPUMASK;
> > > > + } else if (single) {
> > > > + pred->op = pred->op == OP_BAND ? OP_EQ : pred->op;
> > >
> > > Nit, the above can be written as:
> > >
> > > pred->op = pret->op != OP_BAND ? : OP_EQ;
> > >
> >
> > Heh. Those are not equivalent. The right way to write this is:
>
> You mean because of my typo?

No, I hadn't seen the s/pred/pret/ typo. Your code does:

if (pred->op != OP_BAND)
pred->op = true;
else
pred->op OP_EQ;

Realy we should probably trigger a static checker warning any time
someone does a compare operations as part of a "x = comparison ?: bar;
Years ago, someone asked me to do that with regards to error codes like:

return ret < 0 ?: -EINVAL;

but I don't remember the results.

regards,
dan carpenter