Re: [PATCH 2/2] perf tests sigtrap: Skip if running on a kernel with sleepable spinlocks

[Marco Elver <elver@google.com>]

On Wed, 29 Nov 2023 at 16:47, Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
>
> From: Arnaldo Carvalho de Melo <acme@redhat.com>
>
> There are issues as reported that need some more investigation on the
> RT kernel front, till that is addressed, skip this test.
>
> This test is already skipped for multiple hardware architectures where
> the tested kernel feature is not supported.
>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Clark Williams <williams@redhat.com>
> Cc: Ian Rogers <irogers@google.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Mike Galbraith <efault@gmx.de>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Link: https://lore.kernel.org/all/e368f2c848d77fbc8d259f44e2055fe469c219cf.camel@gmx.de/
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Acked-by: Marco Elver <elver@google.com>

> ---
>  tools/perf/tests/sigtrap.c | 46 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/tests/sigtrap.c b/tools/perf/tests/sigtrap.c
> index a1bc7c776254ed2f..e6fd934b027a3d0c 100644
> --- a/tools/perf/tests/sigtrap.c
> +++ b/tools/perf/tests/sigtrap.c
> @@ -103,6 +103,34 @@ static bool attr_has_sigtrap(void)
>
>         return __btf_type__find_member_by_name(id, "sigtrap") != NULL;
>  }
> +
> +static bool kernel_with_sleepable_spinlocks(void)
> +{
> +       const struct btf_member *member;
> +       const struct btf_type *type;
> +       const char *type_name;
> +       int id;
> +
> +       if (!btf__available())
> +               return false;
> +
> +       id = btf__find_by_name_kind(btf, "spinlock", BTF_KIND_STRUCT);
> +       if (id < 0)
> +               return false;
> +
> +       // Only RT has a "lock" member for "struct spinlock"
> +       member = __btf_type__find_member_by_name(id, "lock");
> +       if (member == NULL)
> +               return false;
> +
> +       // But check its type as well
> +       type = btf__type_by_id(btf, member->type);
> +       if (!type || !btf_is_struct(type))
> +               return false;
> +
> +       type_name = btf__name_by_offset(btf, type->name_off);
> +       return type_name && !strcmp(type_name, "rt_mutex_base");
> +}
>  #else  /* !HAVE_BPF_SKEL */
>  static bool attr_has_sigtrap(void)
>  {
> @@ -125,6 +153,11 @@ static bool attr_has_sigtrap(void)
>         return ret;
>  }
>
> +static bool kernel_with_sleepable_spinlocks(void)
> +{
> +       return false;
> +}
> +
>  static void btf__exit(void)
>  {
>  }
> @@ -166,7 +199,7 @@ static int run_test_threads(pthread_t *threads, pthread_barrier_t *barrier)
>
>  static int run_stress_test(int fd, pthread_t *threads, pthread_barrier_t *barrier)
>  {
> -       int ret;
> +       int ret, expected_sigtraps;
>
>         ctx.iterate_on = 3000;
>
> @@ -175,7 +208,16 @@ static int run_stress_test(int fd, pthread_t *threads, pthread_barrier_t *barrie
>         ret = run_test_threads(threads, barrier);
>         TEST_ASSERT_EQUAL("disable failed", ioctl(fd, PERF_EVENT_IOC_DISABLE, 0), 0);
>
> -       TEST_ASSERT_EQUAL("unexpected sigtraps", ctx.signal_count, NUM_THREADS * ctx.iterate_on);
> +       expected_sigtraps = NUM_THREADS * ctx.iterate_on;
> +
> +       if (ctx.signal_count < expected_sigtraps && kernel_with_sleepable_spinlocks()) {
> +               pr_debug("Expected %d sigtraps, got %d, running on a kernel with sleepable spinlocks.\n",
> +                        expected_sigtraps, ctx.signal_count);
> +               pr_debug("See https://lore.kernel.org/all/e368f2c848d77fbc8d259f44e2055fe469c219cf.camel@gmx.de/\n");

No changes from the RT side since? A fix exists, but apparently not
good enough... Sigh.

> +               return TEST_SKIP;
> +       } else
> +               TEST_ASSERT_EQUAL("unexpected sigtraps", ctx.signal_count, expected_sigtraps);
> +
>         TEST_ASSERT_EQUAL("missing signals or incorrectly delivered", ctx.tids_want_signal, 0);
>         TEST_ASSERT_VAL("unexpected si_addr", ctx.first_siginfo.si_addr == &ctx.iterate_on);
>  #if 0 /* FIXME: enable when libc's signal.h has si_perf_{type,data} */
> --
> 2.41.0
>