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Message-ID: <818e43447651af1a659993897c14d05fec5038e4.camel@gmail.com>
Subject: Re: [PATCH RFC bpf-next v3 04/16] bpf/helpers: introduce sleepable
 bpf_timers
From: Eduard Zingerman <eddyz87@gmail.com>
To: Benjamin Tissoires <bentiss@kernel.org>, Alexei Starovoitov
 <ast@kernel.org>,  Daniel Borkmann <daniel@iogearbox.net>, John Fastabend
 <john.fastabend@gmail.com>, Andrii Nakryiko <andrii@kernel.org>, Martin
 KaFai Lau <martin.lau@linux.dev>, Song Liu <song@kernel.org>, Yonghong Song
 <yonghong.song@linux.dev>, KP Singh <kpsingh@kernel.org>, Stanislav
 Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>, Jiri Olsa
 <jolsa@kernel.org>, Jiri Kosina <jikos@kernel.org>,  Benjamin Tissoires
 <benjamin.tissoires@redhat.com>, Jonathan Corbet <corbet@lwn.net>, Shuah
 Khan <shuah@kernel.org>
Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-input@vger.kernel.org, linux-doc@vger.kernel.org, 
	linux-kselftest@vger.kernel.org
Date: Fri, 23 Feb 2024 00:40:23 +0200
In-Reply-To: <20240221-hid-bpf-sleepable-v3-4-1fb378ca6301@kernel.org>
References: <20240221-hid-bpf-sleepable-v3-0-1fb378ca6301@kernel.org>
	 <20240221-hid-bpf-sleepable-v3-4-1fb378ca6301@kernel.org>
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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
> =20
>  	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_SLEEP=
ABLE))
>  		return -EINVAL;
>  	__bpf_spin_lock_irqsave(&timer->lock);
>  	t =3D 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 |=3D HRTIMER_MODE_PINNED;
> =20
> -	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.