Re: [PATCH bpf-next 2/2] selftests/bpf: Verify no warning when close fexit link

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Jul 21, 2026 at 09:30:35PM +0800, Leon Hwang wrote:
> Add a test to verify that there's no WARNING when detaching fexit link by
> following the repro steps of previous commit.
> 
> Without the fix, the WARNING could be triggered by this test.
> 
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>

left 2 nits below

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> ---
>  .../selftests/bpf/prog_tests/tailcalls.c      | 51 +++++++++++++++++++
>  1 file changed, 51 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> index c66037162da5..86d87d5817cf 100644
> --- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> +++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> @@ -13,6 +13,8 @@
>  #include "tailcall_cgrp_storage.skel.h"
>  #include "tailcall_sleepable.skel.h"
>  #include "tailcall_callback.skel.h"
> +#include "tailcall_bpf2bpf2.skel.h"
> +#include "tailcall_bpf2bpf_fexit.skel.h"
>  
>  /* test_tailcall_1 checks basic functionality by patching multiple locations
>   * in a single program for a single tail call slot with nop->jmp, jmp->nop
> @@ -1907,6 +1909,53 @@ static void test_tailcall_callback(void)
>  	RUN_TESTS(tailcall_callback);
>  }
>  
> +static void test_tailcall_bpf2bpf_fexit_links(void)
> +{
> +	struct tailcall_bpf2bpf_fexit *skel1 = NULL, *skel2 = NULL;
> +	struct tailcall_bpf2bpf2 *skel_tc;
> +	struct bpf_link *link;
> +	int err, prog_fd;
> +
> +	skel_tc = tailcall_bpf2bpf2__open_and_load();
> +	if (!ASSERT_OK_PTR(skel_tc, "tailcall_bpf2bpf2__open_and_load"))
> +		return;
> +
> +	skel1 = tailcall_bpf2bpf_fexit__open();
> +	if (!ASSERT_OK_PTR(skel1, "tailcall_bpf2bpf_fexit__open"))
> +		goto out;
> +
> +	prog_fd = bpf_program__fd(skel_tc->progs.classifier_0);
> +	err = bpf_program__set_attach_target(skel1->progs.fexit, prog_fd, "subprog_tail");
> +	if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
> +		goto out;
> +
> +	err = tailcall_bpf2bpf_fexit__load(skel1);
> +	if (!ASSERT_OK(err, "tailcall_bpf2bpf_fexit__load"))
> +		goto out;
> +
> +	link = bpf_program__attach_trace(skel1->progs.fexit);
> +	if (!ASSERT_OK_PTR(link, "bpf_program__attach_trace"))
> +		goto out;
> +	skel1->links.fexit = link;

nit, you could use skel1->links.fexit directly and remove link

> +
> +	skel2 = tailcall_bpf2bpf_fexit__open();
> +	if (!ASSERT_OK_PTR(skel2, "tailcall_bpf2bpf_fexit__open"))
> +		goto out;
> +
> +	err = bpf_program__set_attach_target(skel2->progs.fexit, prog_fd, "subprog_tail");
> +	if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
> +		goto out;
> +
> +	err = tailcall_bpf2bpf_fexit__load(skel2);
> +	if (!ASSERT_OK(err, "tailcall_bpf2bpf_fexit__load"))
> +		goto out;

nit, no need to if/goto, just ASSERT_OK would be enough

> +
> +out:
> +	tailcall_bpf2bpf_fexit__destroy(skel1);
> +	tailcall_bpf2bpf_fexit__destroy(skel2);
> +	tailcall_bpf2bpf2__destroy(skel_tc);
> +}
> +
>  void test_tailcalls(void)
>  {
>  	if (test__start_subtest("tailcall_1"))
> @@ -1974,4 +2023,6 @@ void test_tailcalls(void)
>  	if (test__start_subtest("tailcall_cgrp_storage_no_storage_bridge"))
>  		test_tailcall_cgrp_storage_no_storage_bridge();
>  	test_tailcall_callback();
> +	if (test__start_subtest("tailcall_bpf2bpf_fexit_links"))
> +		test_tailcall_bpf2bpf_fexit_links();
>  }
> -- 
> 2.55.0
>