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

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Message-ID: <CAEf4BzaSqWudSq6tEW3g+szAbcf+n4RO4T2wTnF2Kof0tSMW5w@mail.gmail.com>
Date: Fri, 13 Dec 2024 13:58:43 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, Song Liu <songliubraving@...com>, 
	Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, Hao Luo <haoluo@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Alan Maguire <alan.maguire@...cle.com>, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 11/13] selftests/bpf: Add hit/attach/detach race
 optimized uprobe test

On Wed, Dec 11, 2024 at 5:36 AM Jiri Olsa <jolsa@...nel.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@...nel.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
>