From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "JP Kobryn" <jp.kobryn@linux.dev>, <mikeba@sentinelone.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>
Cc: "Martin KaFai Lau" <martin.lau@linux.dev>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Song Liu" <song@kernel.org>,
"Yonghong Song" <yonghong.song@linux.dev>,
"Jiri Olsa" <jolsa@kernel.org>,
"John Fastabend" <john.fastabend@gmail.com>,
"Shuah Khan" <shuah@kernel.org>, <bpf@vger.kernel.org>,
<linux-kselftest@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC bpf-next 0/2] bpf: Do not let preemption cause false recursion drops in trampoline progs
Date: Wed, 04 Nov 2026 02:21:11 +0000 [thread overview]
Message-ID: <DMM2G9OX9ACV.231CHJEPK0OHU@gmail.com> (raw)
In-Reply-To: <e3f63654-0f7c-462b-b58d-05f3164fe340@linux.dev>
On Tue Nov 3, 2026 at 11:46 PM UTC, JP Kobryn wrote:
> On 10/30/26 3:22 PM, Alexei Starovoitov wrote:
>> On Sun, Oct 25, 2026 at 04:02 AM Mike Bazov via B4 Relay <devnull+mikeba.sentinelone.com@kernel.org> wrote:
>>
>>> Is disabling preemption in __bpf_prog_enter_recur() on !PREEMPT_RT the
>>> preferred fix for fentry/fexit, or would you prefer a different
>>> mechanism for reconciling preemptible execution with prog->active and
>>> the per-CPU private stack?
>>
>> No.
>> We cannot disable preemption, since progs are not short
>> with may_goto they can take 1/4 sec.
>
>
> Seeing this issue as well. This patch opts in ALL non-sleepable programs
> with trampolines. Alexei, would your thoughts be the same if there was
> an opt-in approach, like a libbpf annotation "fentry.nonpreempt", for
> select programs? A patch like this could then check if
> program->nonpreempt is set.
I don't think it's a good idea. Try bpf_preemt_disable(), as I mentioned
in the other reply.
prev parent reply other threads:[~2026-11-04 2:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-25 11:02 Mike Bazov via B4 Relay
2026-10-25 11:02 ` [PATCH RFC bpf-next 1/2] bpf: Keep recursion-checked trampoline programs non-preemptible on !PREEMPT_RT Mike Bazov via B4 Relay
2026-10-25 11:02 ` [PATCH RFC bpf-next 2/2] selftests/bpf: Add trampoline preemption false-recursion test Mike Bazov via B4 Relay
2026-10-30 22:22 ` [PATCH RFC bpf-next 0/2] bpf: Do not let preemption cause false recursion drops in trampoline progs Alexei Starovoitov
2026-11-02 23:24 ` [EXT.MSG] " Mike Bazov
2026-11-03 1:49 ` Alexei Starovoitov
2026-11-03 21:28 ` Mike Bazov
2026-11-04 2:20 ` Alexei Starovoitov
2026-11-03 23:46 ` JP Kobryn
2026-11-04 2:21 ` Alexei Starovoitov [this message]
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