On Thu, 27 Apr 2023 22:22:22 +0800 Yafang Shao <laoar.shao@xxxxxxxxx> wrote: > IIUC, the acquire/release pair works as follows, > > test_recursion_try_acquire > [ protection area ] > test_recursion_release > > After release, there will be no protection, and thus it will fail the > tools/testing/selftests/bpf/progs/recursion.c[1] test case, because > the recursion occurs in the bpf_prog_run() itself, But bpf programs are allowed to recurs. Hence, you need separate logic to detect that. The test_recursion_*() code is for cases that are not allowed to recurs. > > __bpf_prog_enter > test_recursion_try_acquire > [...] > test_recursion_release > // no protection after the release > bpf_prog_run() > bpf_prog_run() // the recursion can't be prevented. But I thought you can run a bpf_prog from another bpf_prog. So you don't want to prevent it. You need other logic to detect if it was not suppose to recurs. -- Steve > __bpf_prog_enter > test_recursion_try_acquire > [...] > test_recursion_release > bpf_prog_run() > bpf_prog_run() > __bpf_prog_enter > test_recursion_try_acquire > [...] > test_recursion_release > bpf_prog_run() > [ And so on ... ] > > [1]. https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/tools/testing/selftests/bpf/progs/recursion.c#n38
