Re: [PATCH RFC bpf-next v6 6/6] selftests/bpf: add sleepable timer tests

On Mon, Apr 8, 2024 at 4:01 PM Eduard Zingerman eddyz87@gmail.com wrote:

...

+SEC("tc") +/* check that calling bpf_timer_start() with a delay on a sleepable

• • callback is returning -EINVAL
• */

+__retval(-22) +long test_call_sleepable_delay(void *ctx) +{

• int key = 2;
  

• struct bpf_timer *timer;
  

• timer = bpf_map_lookup_elem(&timer_map, &key);
  

• if (!timer)
  

•         return 1;
  

• if (bpf_timer_init(timer, &timer_map, CLOCK_MONOTONIC | BPF_F_TIMER_SLEEPABLE))
  

•         return 2;
  

• if (bpf_timer_set_sleepable_cb(timer, timer_cb_sleepable))
  

•         return 3;
  

• return bpf_timer_start(timer, 1, 0);
  

Q: should verifier statically check that 3rd parameter is zero for sleepable timers? (same question for call to bpf_timer_set_sleepable_cb() with non-sleepable map)

It can, but that sounds like more work for the verifier. Which gives more reasons to use new kfuncs and clean start with bpf_wq.