Re: [PATCH bpf-next 2/2] selftests/bpf: Test RCU iterator state pruning
Eduard Zingerman <[email protected]>
| Newsgroups | org.kernel.vger.linux-kselftest,org.kernel.vger.bpf,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
On Thu, 2026-08-06 at 17:43 -0700, Ning Ding wrote:
...
> +SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
> +__failure __msg("expected an RCU CS when using bpf_iter_task_next")
> +__flag(BPF_F_TEST_STATE_FREQ)
> +int BPF_PROG(iter_tasks_rcu_state_pruning)
> +{
> + struct bpf_iter_task it;
> +
> + bpf_rcu_read_lock();
> + bpf_iter_task_new(&it, NULL, BPF_TASK_ITER_ALL_PROCS);
> +
> + if (likely(bpf_get_prandom_u32())) {
Could you please convert this test to inline assembly?
The presence of 'likely' might not be sufficient to guarantee
the codegen pattern, so we usually resort to the assembly for
tests where that is important.
> + /* Keep the outer RCU lock active. */
> + bpf_rcu_read_lock();
> + bpf_rcu_read_unlock();
> + } else {
> + /* Create an unprotected gap. */
> + bpf_rcu_read_unlock();
> + bpf_rcu_read_lock();
> + }
> +
> + bpf_iter_task_next(&it);
> + bpf_iter_task_destroy(&it);
> + bpf_rcu_read_unlock();
> +
> + return 0;
> +}
> +
> SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
> __failure __msg("expected an RCU CS when using bpf_iter_css_next")
> int BPF_PROG(iter_css_lock_and_unlock)