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

[Jiri Olsa <olsajiri@gmail.com>]

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