linux-kernel - Re: [PATCH] perf test: Skip sigtrap test on old kernels

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Date:   Tue, 6 Sep 2022 09:45:08 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Marco Elver <elver@...gle.com>
Cc:     Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf test: Skip sigtrap test on old kernels

Em Sat, Sep 03, 2022 at 08:52:01AM +0200, Marco Elver escreveu:
> On Sat, 3 Sept 2022 at 02:02, Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > If it runs on an old kernel, perf_event_open would fail because of the
> > new fields sigtrap and sig_data.  Just skip the test if it failed.
> >
> > Cc: Marco Elver <elver@...gle.com>
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/tests/sigtrap.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/tools/perf/tests/sigtrap.c b/tools/perf/tests/sigtrap.c
> > index e32ece90e164..7057566e6ae4 100644
> > --- a/tools/perf/tests/sigtrap.c
> > +++ b/tools/perf/tests/sigtrap.c
> > @@ -140,6 +140,7 @@ static int test__sigtrap(struct test_suite *test __maybe_unused, int subtest __m
> >         fd = sys_perf_event_open(&attr, 0, -1, -1, perf_event_open_cloexec_flag());
> >         if (fd < 0) {
> >                 pr_debug("FAILED sys_perf_event_open(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf)));
> > +               ret = TEST_SKIP;
> 
> Wouldn't we be interested if perf_event_open() fails because it could
> actually be a bug? By skipping we'll be more likely to miss the fact
> there's a real problem.
> 
> That's my naive thinking at least - what do other perf tests usually
> do in this case?

Yeah, I was going to try and check if this is the only way that, with
the given arguments, perf_event_open would fail, but its better to at
least check errno against -EINVAL or something?

- Arnaldo