From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Mike Bazov" <mikeba@sentinelone.com>
Cc: "Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"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: [EXT.MSG] Re: [PATCH RFC bpf-next 0/2] bpf: Do not let preemption cause false recursion drops in trampoline progs
Date: Tue, 03 Nov 2026 01:49:12 +0000 [thread overview]
Message-ID: <DML75890DWIX.EYB690LPBM1O@gmail.com> (raw)
In-Reply-To: <CAPnbwjrB_je6jXt3BGD-1q1yFs_wFd-Yh9KzixKzLK_X3Stuag@mail.gmail.com>
On Mon, Nov 02, 2026 at 03:24 PM Mike Bazov <mikeba@sentinelone.com> wrote:
> To fix fentry/fexit while keeping preemption enabled, we'll need to:
> 1. Disable private stack for fentry/fexit (so each task uses its own
> kernel stack), and
Yes.
Then the stack limit covers the whole call chain instead of one frame.
It's 2 Kbytes on x86-64 and arm64 now.
> 2. Check recursion in __bpf_prog_enter_recur() per-task rather than via
> the per-CPU prog->active counter (still blocking same-task recursion
> and IRQ/NMI re-entry on the same CPU, while allowing a preempting
> Task B to run).
No. I don't think we can switch to per-task that easily.
For your use case try fsession. It was added specifically to match entry/exit.
next prev parent reply other threads:[~2026-11-03 1:49 UTC|newest]
Thread overview: 29+ 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 ` Mike Bazov
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 ` Mike Bazov
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
2026-10-25 11:02 ` Mike Bazov
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 [this message]
2026-11-03 21:28 ` Mike Bazov
2026-11-04 2:20 ` Alexei Starovoitov
2026-11-05 1:12 ` Martin Kelly
2026-11-05 5:18 ` Alexei Starovoitov
2026-11-05 8:53 ` Peter Zijlstra
2026-11-05 20:16 ` Martin Kelly
2026-11-05 12:26 ` Peter Zijlstra
2026-11-05 20:44 ` Martin Kelly
2026-11-03 23:46 ` JP Kobryn
2026-11-04 2:21 ` Alexei Starovoitov
2026-11-05 0:12 ` [EXT.MSG] " Mike Bazov
2026-11-05 5:14 ` Alexei Starovoitov
2026-11-05 21:10 ` Martin Kelly
2026-11-05 23:35 ` Mike Bazov
2026-11-06 22:08 ` Andrii Nakryiko
2026-11-07 21:32 ` Mike Bazov
2026-11-10 0:12 ` JP Kobryn (CrowdStrike)
2026-11-10 20:43 ` Mike Bazov
2026-11-11 2:58 ` JP Kobryn (CrowdStrike)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=DML75890DWIX.EYB690LPBM1O@gmail.com \
--to=alexei.starovoitov@gmail.com \
--cc=andrii@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=eddyz87@gmail.com \
--cc=john.fastabend@gmail.com \
--cc=jolsa@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=martin.lau@linux.dev \
--cc=memxor@gmail.com \
--cc=mikeba@sentinelone.com \
--cc=shuah@kernel.org \
--cc=song@kernel.org \
--cc=yonghong.song@linux.dev \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.