Re: [PATCH bpf-next 11/13] selftests/bpf: Add hit/attach/detach race optimized uprobe test

Andrii Nakryiko
2024-12-13T21:58:59Z

On Wed, Dec 11, 2024 at 5:36 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding test that makes sure parallel execution of the uprobe and
> attach/detach of optimized uprobe on it works properly.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> .../selftests/bpf/prog_tests/uprobe_syscall.c | 82 +++++++++++++++++++
> 1 file changed, 82 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> index 1dbc26a1130c..eacd14db8f8d 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> @@ -532,6 +532,81 @@ static void test_uprobe_usdt(void)
> cleanup:
> uprobe_optimized__destroy(skel);
> }
> +
> +static bool race_stop;

volatile?

> +
> +static void *worker_trigger(void *arg)
> +{
> + unsigned long rounds = 0;
> +
> + while (!race_stop) {
> + uprobe_test();
> + rounds++;
> + }
> +
> + printf("tid %d trigger rounds: %lu\n", gettid(), rounds);
> + return NULL;
> +}
> +
> +static void *worker_attach(void *arg)
> +{
> + struct uprobe_optimized *skel;
> + unsigned long rounds = 0;
> +
> + skel = uprobe_optimized__open_and_load();
> + if (!ASSERT_OK_PTR(skel, "uprobe_optimized__open_and_load"))
> + goto cleanup;
> +
> + while (!race_stop) {
> + skel->links.test_2 = bpf_program__attach_uprobe_multi(skel->progs.test_2, -1,
> + "/proc/self/exe", "uprobe_test_nop5", NULL);
> + if (!ASSERT_OK_PTR(skel->links.test_2, "bpf_program__attach_uprobe_multi"))
> + break;
> + bpf_link__destroy(skel->links.test_2);
> + skel->links.test_2 = NULL;
> + rounds++;
> + }
> +
> + printf("tid %d attach rounds: %lu hits: %lu\n", gettid(), rounds, skel->bss->executed);
> +
> +cleanup:
> + uprobe_optimized__destroy(skel);
> + return NULL;
> +}
> +
> +static void test_uprobe_race(void)
> +{
> + int err, i, nr_cpus, nr;
> + pthread_t *threads;
> +
> + nr_cpus = libbpf_num_possible_cpus();

check whitespaces

> + if (!ASSERT_GE(nr_cpus, 0, "nr_cpus"))
> + return;
> +
> + nr = nr_cpus * 2;
> + threads = malloc(sizeof(*threads) * nr);
> + if (!ASSERT_OK_PTR(threads, "malloc"))
> + return;
> +
> + for (i = 0; i < nr_cpus; i++) {
> + err = pthread_create(&threads[i], NULL, worker_trigger, NULL);
> + if (!ASSERT_OK(err, "pthread_create"))
> + goto cleanup;
> + }
> +
> + for (; i < nr; i++) {
> + err = pthread_create(&threads[i], NULL, worker_attach, NULL);
> + if (!ASSERT_OK(err, "pthread_create"))
> + goto cleanup;
> + }
> +
> + sleep(4);
> +
> +cleanup:
> + race_stop = true;
> + for (i = 0; i < nr; i++)
> + pthread_join(threads[i], NULL);

what happens with pthread_join() when called with uninitialized
threads[i] (e.g., when error happens in the middle of creating
threads)?

> +}
> #else
> static void test_uretprobe_regs_equal(void)
> {
> @@ -567,6 +642,11 @@ static void test_uprobe_usdt(void)
> {
> test__skip();
> }
> +
> +static void test_uprobe_race(void)
> +{
> + test__skip();
> +}
> #endif
>
> void test_uprobe_syscall(void)
> @@ -585,4 +665,6 @@ void test_uprobe_syscall(void)
> test_uprobe_multi();
> if (test__start_subtest("uprobe_usdt"))
> test_uprobe_usdt();
> + if (test__start_subtest("uprobe_race"))
> + test_uprobe_race();
> }
> --
> 2.47.0
>