From: JP Kobryn <jp.kobryn@linux.dev>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
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: Tue, 3 Nov 2026 15:46:27 -0800 [thread overview]
Message-ID: <e3f63654-0f7c-462b-b58d-05f3164fe340@linux.dev> (raw)
In-Reply-To: <DMIIV9CE0PN4.309YUGIXQUZNF@gmail.com>
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.
next prev parent reply other threads:[~2026-11-03 23:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-25 11:02 [PATCH RFC bpf-next 0/2] bpf: Do not let preemption cause false recursion drops in trampoline progs 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 11:38 ` sashiko-bot
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 [this message]
2026-11-04 2:21 ` Alexei Starovoitov
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