Re: [PATCH bpf] selftests/bpf: Run test_perf_branches more than 1 time

[Alexei Starovoitov]

On Wed, Apr 8, 2026 at 2:57 AM Maya Matuszczyk
<mayamatuszczyk@xxxxxxxxxx> wrote:
>
> test_perf_branches bpf program was only being ran once, and
> perf_branches test would fail if the only sample that was passed to
> test_perf_branches didn't have branch data.
> Fix those failures by running it a few more times and waiting until a valid
> sample shows up, and leave the perf event only enabled for the duration of
> test spins.
>
> Signed-off-by: Maya Matuszczyk <mayamatuszczyk@xxxxxxxxxx>
> ---
>  .../selftests/bpf/prog_tests/perf_branches.c  | 57 +++++++++++++------
>  .../selftests/bpf/progs/test_perf_branches.c  | 11 ++--
>  2 files changed, 43 insertions(+), 25 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/perf_branches.c b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
> index 0a7ef770c487..1dcb7c70f545 100644
> --- a/tools/testing/selftests/bpf/prog_tests/perf_branches.c
> +++ b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
> @@ -15,10 +15,6 @@ static void check_good_sample(struct test_perf_branches *skel)
>         int pbe_size = sizeof(struct perf_branch_entry);
>         int duration = 0;
>
> -       if (CHECK(!skel->bss->run_cnt, "invalid run_cnt",
> -                 "checked sample validity before prog run"))
> -               return;
> -
>         if (CHECK(!skel->bss->valid, "output not valid",
>                  "no valid sample from prog"))
>                 return;
> @@ -49,10 +45,6 @@ static void check_bad_sample(struct test_perf_branches *skel)
>         int written_stack = skel->bss->written_stack_out;
>         int duration = 0;
>
> -       if (CHECK(!skel->bss->run_cnt, "invalid run_cnt",
> -                 "checked sample validity before prog run"))
> -               return;
> -
>         if (CHECK(!skel->bss->valid, "output not valid",
>                  "no valid sample from prog"))
>                 return;
> @@ -73,7 +65,6 @@ static void test_perf_branches_common(int perf_fd,
>         bool detached = false;
>         struct bpf_link *link;
>         volatile int j = 0;
> -       cpu_set_t cpu_set;
>
>         skel = test_perf_branches__open_and_load();
>         if (CHECK(!skel, "test_perf_branches_load",
> @@ -85,19 +76,35 @@ static void test_perf_branches_common(int perf_fd,
>         if (!ASSERT_OK_PTR(link, "attach_perf_event"))
>                 goto out_destroy_skel;
>
> -       /* generate some branches on cpu 0 */
> -       CPU_ZERO(&cpu_set);
> -       CPU_SET(0, &cpu_set);
> -       err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set);
> -       if (CHECK(err, "set_affinity", "cpu #0, err %d\n", err))
> +       err = ioctl(perf_fd, PERF_EVENT_IOC_RESET, 0);
> +       if (CHECK(err == -1, "perf event reset", "ioctl err %d", errno))
>                 goto out_destroy;

Since you're touching this part, please use ASSERT*() macros,
since CHECK() is deprecated.

sashiko thinks the same.