Re: [PATCH bpf-next v4 3/6] bpf/helpers: introduce bpf_timer_set_sleepable_cb() kfunc

On Mon, Mar 18, 2024 at 11:52 PM Eduard Zingerman eddyz87@gmail.com wrote:

On Fri, 2024-03-15 at 15:29 +0100, Benjamin Tissoires wrote:

This patch looks good to me, please see two nitpicks below. Acked-by: Eduard Zingerman eddyz87@gmail.com

Thanks!

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@@ -1350,6 +1358,11 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla goto out; }

• if (t->is_sleepable && !(flags & BPF_F_TIMER_SLEEPABLE)) {
  

•         ret = -EINVAL;
  

•         goto out;
  

• }
  

Nit: the BPF_F_TIMER_ABS and BPF_F_TIMER_CPU_PIN don't affect sleepable timers, should this check be changed to: '(t->is_sleepable && flags != BPF_F_TIMER_SLEEPABLE)' ?

Sounds fair enough. Scheduled this for v5

[...]

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@@ -12151,6 +12175,16 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, } }

• if (is_async_callback_calling_kfunc(meta.func_id)) {
  

•         err = push_callback_call(env, insn, insn_idx, meta.subprogno,
  

•                                  set_timer_callback_state);
  

Nit: still think that this fragment would be better as:

    if (is_bpf_timer_set_sleepable_cb_impl_kfunc(meta.func_id)) {
            err = push_callback_call(env, insn, insn_idx, meta.subprogno,
                                     set_timer_callback_state);

Because of the 'set_timer_callback_state' passed to push_callback_call().

Yeah, sorry I missed that part from the previous reviews.

Fixed in v5

Cheers, Benjamin

...

•         if (err) {
  

•                 verbose(env, "kfunc %s#%d failed callback verification\n",
  

•                         func_name, meta.func_id);
  

•                 return err;
  

•         }
  

• }
  

• rcu_lock = is_kfunc_bpf_rcu_read_lock(&meta);
  rcu_unlock = is_kfunc_bpf_rcu_read_unlock(&meta);