Re: [PATCH RFC bpf-next v6 6/6] selftests/bpf: add sleepable timer tests

[Eduard Zingerman <eddyz87@gmail.com>]

On Mon, 2024-04-08 at 10:09 +0200, Benjamin Tissoires wrote:
> bpf_experimental.h and ../bpf_testmod/bpf_testmod_kfunc.h are both
> including vmlinux.h, which is not compatible with including time.h
> or bpf_tcp_helpers.h.
> 
> So keep sleepable tests in a separate bpf source file.
> 
> The first correct test is run twice for convenience:
> - first through RUN_TESTS
> - then we ensure that the timer was actually executed, in a manual
>   load/attach/run
> 
> Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
> 
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
(With a few nitpicks)

> diff --git a/tools/testing/selftests/bpf/prog_tests/timer.c b/tools/testing/selftests/bpf/prog_tests/timer.c
> index d66687f1ee6a..c6c7c623b31c 100644
> --- a/tools/testing/selftests/bpf/prog_tests/timer.c
> +++ b/tools/testing/selftests/bpf/prog_tests/timer.c

[...]

> +void serial_test_sleepable_timer(void)
> +{
> +	struct timer_sleepable *timer_sleepable_skel = NULL;
> +	int err, prog_fd;
> +
> +	LIBBPF_OPTS(bpf_test_run_opts, topts);
> +
> +	RUN_TESTS(timer_sleepable);
> +
> +	/* re-run the success test to check if the timer was actually executed */
> +
> +	timer_sleepable_skel = timer_sleepable__open_and_load();
> +	if (!ASSERT_OK_PTR(timer_sleepable_skel, "timer_sleepable_skel_load"))
> +		return;
> +
> +	err = timer_sleepable__attach(timer_sleepable_skel);
> +	if (!ASSERT_OK(err, "timer_sleepable_attach"))
> +		return;

Nit: this should call timer_sleepable__destroy();

> +
> +	prog_fd = bpf_program__fd(timer_sleepable_skel->progs.test_syscall_sleepable);
> +	err = bpf_prog_test_run_opts(prog_fd, &topts);
> +	ASSERT_OK(err, "test_run");
> +	ASSERT_EQ(topts.retval, 0, "test_run");
> +
> +	usleep(50); /* 10 usecs should be enough, but give it extra */
> +
> +	ASSERT_EQ(timer_sleepable_skel->bss->ok_sleepable, 1, "ok_sleepable");

Nit: same as above.

> +}
> diff --git a/tools/testing/selftests/bpf/progs/timer_sleepable.c b/tools/testing/selftests/bpf/progs/timer_sleepable.c
> new file mode 100644
> index 000000000000..fc7829d8b6c4
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/timer_sleepable.c

[...]

> +SEC("tc")
> +/* check that calling bpf_timer_start() with BPF_F_TIMER_SLEEPABLE on a sleepable
> + * callback works
> + */
> +__retval(0)
> +long test_call_sleepable(void *ctx)
> +{
> +	int key = 0;
> +	struct bpf_timer *timer;
> +
> +	if (ok_sleepable & 1)
> +		return -1;
> +
> +	timer = bpf_map_lookup_elem(&timer_map, &key);
> +	if (timer) {
> +		if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE) != 0)
> +			return -2;
> +		bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable);
> +		if (bpf_timer_start(timer, 0, 0))
> +			return -3;
> +	} else {
> +		return -4;
> +	}
> +
> +	return 0;
> +}
> +
> +SEC("syscall")
> +/* check that calling bpf_timer_start() with BPF_F_TIMER_SLEEPABLE on a sleepable
> + * callback works.
> + */
> +__retval(0)
> +long test_syscall_sleepable(void *ctx)
> +{

Nit: the body of this function is the same as in test_call_sleepable(),
     maybe factor it out as an auxiliary static function?
     (also, should these tests use different 'key' ?)

> +	int key = 0;
> +	struct bpf_timer *timer;
> +
> +	if (ok_sleepable & 1)
> +		return -1;
> +
> +	timer = bpf_map_lookup_elem(&timer_map, &key);
> +	if (timer) {
> +		if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE) != 0)
> +			return -2;
> +		bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable);
> +		if (bpf_timer_start(timer, 0, 0))
> +			return -3;
> +	} else {
> +		return -4;
> +	}
> +
> +	return 0;
> +}

[...]

> +SEC("tc")
> +/* check that calling bpf_timer_start() with a delay on a sleepable
> + * callback is returning -EINVAL
> + */
> +__retval(-22)
> +long test_call_sleepable_delay(void *ctx)
> +{
> +	int key = 2;
> +	struct bpf_timer *timer;
> +
> +	timer = bpf_map_lookup_elem(&timer_map, &key);
> +	if (!timer)
> +		return 1;
> +
> +	if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE))
> +		return 2;
> +
> +	if (bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable))
> +		return 3;
> +
> +	return bpf_timer_start(timer, 1, 0);

Q: should verifier statically check that 3rd parameter is zero for sleepable timers?
  (same question for call to bpf_timer_set_sleepable_cb() with non-sleepable map)

[...]