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From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.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>, Eduard Zingerman <eddyz87@gmail.com>,
 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, Benjamin Tissoires <bentiss@kernel.org>
Subject: Re: [PATCH RFC bpf-next v2 02/10] bpf/helpers: introduce sleepable
 timers
In-Reply-To: <20240214-hid-bpf-sleepable-v2-2-5756b054724d@kernel.org>
References: <20240214-hid-bpf-sleepable-v2-0-5756b054724d@kernel.org>
 <20240214-hid-bpf-sleepable-v2-2-5756b054724d@kernel.org>
Date: Fri, 16 Feb 2024 15:20:06 +0100
Message-ID: <87bk8gcwyx.fsf@toke.dk>
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Just one comment on one of your FIXMEs:

> +	rcu_assign_pointer(t->sleepable_cb_fn, NULL);
> +	/* FIXME: probably do something about the SLEEPABLE flag */

I guess we should store the flag in the timer struct somewhere, and then
restrict the set_callback() functions so that the regular variant only
works without the flag set, and the _sleepable version only works if the
flag is set? Otherwise we may end up calling a non-sleepable function in
sleepable context or vise versa...

-Toke