Re: [PATCH bpf-next 2/2] selftests/bpf: Add testcases for callback with tailcall

[Pu Lehui]

Hi Eduard,

Thanks for reviewing.

On 2026/7/14 6:12, Eduard Zingerman wrote:
> On Sat, 2026-07-11 at 10:47 +0000, Pu Lehui wrote:
>
> [...]
>
> > diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> > index a5a226d0104c..c66037162da5 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
>
> [...]
>
> >   void test_tailcalls(void)
> >   {
> >   	if (test__start_subtest("tailcall_1"))
> > @@ -1967,4 +1973,5 @@ void test_tailcalls(void)
> >   		test_tailcall_cgrp_storage_no_storage_leaf();
> >   	if (test__start_subtest("tailcall_cgrp_storage_no_storage_bridge"))
> >   		test_tailcall_cgrp_storage_no_storage_bridge();
> > +	test_tailcall_callback();
>
> Please use test__start_subtest().

I use `RUN_TESTS(tailcall_callback)` above, so it will parse subtest 
base on `__description(desc)` or test func_proto. Also, it will make 
sense to test only by `test_progs -a tailcalls/tailcall_bpf2bpf_callback`


But if use `test__start_subtest`, it will show double test items:

#480/37  tailcalls/tailcall_cgrp_storage_no_storage_bridge:OK
#480/38  tailcalls/test_tailcall_bpf2bpf_callback:OK <--
#480/39  tailcalls/tailcall_bpf2bpf_callback:OK <--
#480     tailcalls:OK
Summary: 1/39 PASSED, 0 SKIPPED, 0 FAILED

> >   }
> > diff --git a/tools/testing/selftests/bpf/progs/tailcall_callback.c b/tools/testing/selftests/bpf/progs/tailcall_callback.c
> > new file mode 100644
> > index 000000000000..504d8e7a6996
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/tailcall_callback.c
>
> [...]
>
> > +/* callback involving 1 subprog with tail call is rejected */
> > +SEC("tc")
> > +__failure __msg("cannot tail call within callback")
> > +int tailcall_bpf2bpf_callback_1(struct __sk_buff *skb)
> > +{
> > +	clobber_regs_stack();
> > +
> > +	bpf_loop(1, callback_loop_2, &skb, 0);
> > +	return 0;
> > +}
>
> I think having all three is a bit redundant,
> let's settle on tailcall_bpf2bpf_callback_1?

make sense to me