Re: [PATCH perf/core 15/22] selftests/bpf: Add hit/attach/detach race optimized uprobe test

Andrii Nakryiko
2025-04-24T16:30:33Z

On Thu, Apr 24, 2025 at 5:51 AM Jiri Olsa <olsajiri@gmail.com> wrote:
>
> On Wed, Apr 23, 2025 at 10:42:43AM -0700, Andrii Nakryiko wrote:
>
> SNIP
>
> > > +
> > > +static void test_uprobe_race(void)
> > > +{
> > > + int err, i, nr_threads;
> > > + pthread_t *threads;
> > > +
> > > + nr_threads = libbpf_num_possible_cpus();
> > > + if (!ASSERT_GE(nr_threads, 0, "libbpf_num_possible_cpus"))
> >
> > I hope there are strictly more than zero CPUs... ;)
> >
> > > + return;
> > > +
> > > + threads = malloc(sizeof(*threads) * nr_threads);
> > > + if (!ASSERT_OK_PTR(threads, "malloc"))
> > > + return;
> > > +
> > > + for (i = 0; i < nr_threads; i++) {
> > > + err = pthread_create(&threads[i], NULL, i % 2 ? worker_trigger : worker_attach,
> > > + NULL);
> >
> > What happens when three is just one CPU?
> >
>
> right, we need at least 2 threads, how about the change below
>
> thanks,
> jirka
>
>
> ---
> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> index d55c3579cebe..c885f097eed4 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
> @@ -701,8 +701,9 @@ static void test_uprobe_race(void)
> pthread_t *threads;
>
> nr_threads = libbpf_num_possible_cpus();
> - if (!ASSERT_GE(nr_threads, 0, "libbpf_num_possible_cpus"))
> + if (!ASSERT_GT(nr_threads, 0, "libbpf_num_possible_cpus"))
> return;
> + nr_threads = max(2, nr_threads);

yep, ack

>
> threads = malloc(sizeof(*threads) * nr_threads);
> if (!ASSERT_OK_PTR(threads, "malloc"))