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

Jiri Olsa
2024-12-16T07:59:16Z

On Fri, Dec 13, 2024 at 01:58:43PM -0800, Andrii Nakryiko wrote:
> 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?

ok

>
> > +
> > +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

ok

>
> > + 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)?

yes, I'll do the proper cleanup in new version

thanks,
jirka