Re: [PATCH RFC bpf-next v3 04/16] bpf/helpers: introduce sleepable bpf_timers

[Eduard Zingerman]

On Wed, 2024-02-21 at 17:25 +0100, Benjamin Tissoires wrote:

[...]

> @@ -1282,7 +1333,7 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla
>  
>  	if (in_nmi())
>  		return -EOPNOTSUPP;
> -	if (flags & ~(BPF_F_TIMER_ABS | BPF_F_TIMER_CPU_PIN))
> +	if (flags & ~(BPF_F_TIMER_ABS | BPF_F_TIMER_CPU_PIN | BPF_F_TIMER_SLEEPABLE))
>  		return -EINVAL;
>  	__bpf_spin_lock_irqsave(&timer->lock);
>  	t = timer->timer;
> @@ -1299,7 +1350,10 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla
>  	if (flags & BPF_F_TIMER_CPU_PIN)
>  		mode |= HRTIMER_MODE_PINNED;
>  
> -	hrtimer_start(&t->timer, ns_to_ktime(nsecs), mode);
> +	if (flags & BPF_F_TIMER_SLEEPABLE)
> +		schedule_work(&t->work);
> +	else
> +		hrtimer_start(&t->timer, ns_to_ktime(nsecs), mode);

It looks like nsecs is simply ignored for sleepable timers.
Should this be hrtimer_start() that waits nsecs and schedules work,
or schedule_delayed_work()? (but it takes delay in jiffies, which is
probably too coarse). Sorry if I miss something.