Re: [PATCH v1 1/2] perf sched: Avoid segv if tp_handler not set

[Ian Rogers]

On Thu, Apr 2, 2026 at 7:42 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> On Tue, Mar 31, 2026 at 10:59:52PM -0700, Ian Rogers wrote:
> > On Thu, Mar 26, 2026 at 4:20 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> > >
> > > On Fri, Mar 20, 2026 at 11:14:47PM -0700, Ian Rogers wrote:
> > > > Doing a `perf sched record` then `perf sched stats report` crashes as
> > > > the tp_handler isn't set. Add extra checks that tp_handler is set
> > > > before accessing through it.
> > >
> > > Oh.. unintended use case. :)  Probably better to add a dummy handler
> > > for `perf sched stats report`.
> >
> > Perhaps. I'd prefer to land the simpler change as-is.
>
> Well.. I guess the dummy handler approach would be simpler and perform
> better. :)
>
> Thanks,
> Namhyung
>
>
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index d083e2bb770303a4..9fb5447f9014d026 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -4955,6 +4955,7 @@ int cmd_sched(int argc, const char **argv)
>                 .switch_event       = replay_switch_event,
>                 .fork_event         = replay_fork_event,
>         };
> +       struct trace_sched_handler stats_ops  = {};

Oh, because there's an existing null test on the function pointer we
don't need dummy functions, which is what I thought you were asking
for. I'm still not convinced this is very intention revealing, but if
it works for you then you can have my reviewed-by tag.

Thanks,
Ian

>         int ret;
>
>         perf_tool__init(&sched.tool, /*ordered_events=*/true);
> @@ -5037,6 +5038,7 @@ int cmd_sched(int argc, const char **argv)
>         } else if (!strcmp(argv[0], "stats")) {
>                 const char *const stats_subcommands[] = {"record", "report", NULL};
>
> +               sched.tp_handler = &stats_ops;
>                 argc = parse_options_subcommand(argc, argv, stats_options,
>                                                 stats_subcommands,
>                                                 stats_usage,
>