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

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Message-ID: <Z1_d0Chz17VZuX9V@krava>
Date: Mon, 16 Dec 2024 08:59:12 +0100
From: Jiri Olsa <olsajiri@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
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 Fri, Dec 13, 2024 at 01:58:43PM -0800, Andrii Nakryiko wrote:
> 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?

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