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From:   Song Liu <songliubraving@fb.com>
To:     KP Singh <kpsingh@chromium.org>
CC:     open list <linux-kernel@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin Lau <kafai@fb.com>, Paul Turner <pjt@google.com>,
        Jann Horn <jannh@google.com>, Hao Luo <haoluo@google.com>
Subject: Re: [PATCH bpf-next v4 1/9] bpf: Allow LSM programs to use bpf spin
 locks
Thread-Topic: [PATCH bpf-next v4 1/9] bpf: Allow LSM programs to use bpf spin
 locks
Thread-Index: AQHWs4KvQRXv4p6YTkGVsnueG+A+cKm54JIA
Date:   Thu, 5 Nov 2020 18:45:15 +0000
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References: <20201105144755.214341-1-kpsingh@chromium.org>
 <20201105144755.214341-2-kpsingh@chromium.org>
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> On Nov 5, 2020, at 6:47 AM, KP Singh <kpsingh@chromium.org> wrote:
>=20
> From: KP Singh <kpsingh@google.com>
>=20
> Usage of spin locks was not allowed for tracing programs due to
> insufficient preemption checks. The verifier does not currently prevent
> LSM programs from using spin locks, but the helpers are not exposed
> via bpf_lsm_func_proto.
>=20
> Based on the discussion in [1], non-sleepable LSM programs should be
> able to use bpf_spin_{lock, unlock}.
>=20
> Sleepable LSM programs can be preempted which means that allowng spin
> locks will need more work (disabling preemption and the verifier
> ensuring that no sleepable helpers are called when a spin lock is held).
>=20
> [1]: https://lore.kernel.org/bpf/20201103153132.2717326-1-kpsingh@chromiu=
m.org/T/#md601a053229287659071600d3483523f752cd2fb
>=20
> Signed-off-by: KP Singh <kpsingh@google.com>

Acked-by: Song Liu <songliubraving@fb.com>

[...]