From: Jiri Olsa <olsajiri@gmail.com>
To: bot+bpf-ci@kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
kafai@fb.com, eddyz87@gmail.com, songliubraving@fb.com,
yhs@fb.com, menglong8.dong@gmail.com, rostedt@kernel.org,
martin.lau@kernel.org, yonghong.song@linux.dev, clm@meta.com,
ihor.solodrai@linux.dev
Subject: Re: [PATCHv2 bpf-next 02/23] bpf: Use mutex lock pool for bpf trampolines
Date: Thu, 5 Mar 2026 15:01:58 +0100 [thread overview]
Message-ID: <aamM1n-ha0LKnry2@krava> (raw)
In-Reply-To: <28376b19ac32833bc93e5688dbb271724f84f19aece2f828c7ca56bbd9706a0f@mail.kernel.org>
On Wed, Mar 04, 2026 at 11:02:28PM +0000, bot+bpf-ci@kernel.org wrote:
> > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> > --- a/kernel/bpf/trampoline.c
> > +++ b/kernel/bpf/trampoline.c
>
> [ ... ]
>
> > @@ -99,12 +127,12 @@ static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, unsigned long ip,
> > * cleanup_direct_functions_after_ipmodify
> > *
> > * In both cases, direct_mutex is already locked. Use
> > - * mutex_trylock(&tr->mutex) to avoid deadlock in race condition
> > + * mutex_trylock(select_trampoline_lock(tr)) to avoid deadlock in race condition
> > * (something else is making changes to this same trampoline).
> > */
> > - if (!mutex_trylock(&tr->mutex)) {
> > - /* sleep 1 ms to make sure whatever holding tr->mutex makes
> > - * some progress.
> > + if (!mutex_trylock(select_trampoline_lock(tr))) {
> > + /* sleep 1 ms to make sure whatever holding select_trampoline_lock(tr)
> > + * makes some progress.
> > */
>
> With a pool of 32 mutexes, the trylock can now also fail because a
> different trampoline that hashes to the same pool entry holds the lock.
> Should the comment say "something else holds the same pool lock" instead
> of "something else is making changes to this same trampoline"?
right, will change the comment, thnx
>
> Similarly, the sleep comment says the holder "makes some progress" but
> with a pool lock the holder could be operating on an entirely unrelated
> trampoline.
this one seems ok to me.. holder is 'whatever holding select_trampoline_lock'
which is correct
jirka
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/22692622038
next prev parent reply other threads:[~2026-03-05 14:02 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-04 22:21 [PATCHv2 bpf-next 00/23] bpf: tracing_multi link Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 01/23] ftrace: Add ftrace_hash_count function Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 02/23] bpf: Use mutex lock pool for bpf trampolines Jiri Olsa
2026-03-04 23:02 ` bot+bpf-ci
2026-03-05 14:01 ` Jiri Olsa [this message]
2026-03-04 22:21 ` [PATCHv2 bpf-next 03/23] bpf: Add struct bpf_trampoline_ops object Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 04/23] bpf: Add struct bpf_tramp_node object Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 05/23] bpf: Factor fsession link to use struct bpf_tramp_node Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 06/23] bpf: Add multi tracing attach types Jiri Olsa
2026-03-04 23:02 ` bot+bpf-ci
2026-03-05 14:02 ` Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 07/23] bpf: Move sleepable verification code to btf_id_allow_sleepable Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 08/23] bpf: Add bpf_trampoline_multi_attach/detach functions Jiri Olsa
2026-03-04 23:02 ` bot+bpf-ci
2026-03-05 14:02 ` Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 09/23] bpf: Add support for tracing multi link Jiri Olsa
2026-03-04 23:02 ` bot+bpf-ci
2026-03-05 14:02 ` Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 10/23] bpf: Add support for tracing_multi link cookies Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 11/23] bpf: Add support for tracing_multi link session Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 12/23] bpf: Add support for tracing_multi link fdinfo Jiri Olsa
2026-03-04 23:02 ` bot+bpf-ci
2026-03-05 14:01 ` Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 13/23] libbpf: Add bpf_object_cleanup_btf function Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 14/23] libbpf: Add bpf_link_create support for tracing_multi link Jiri Olsa
2026-03-04 23:02 ` bot+bpf-ci
2026-03-05 14:01 ` Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 15/23] libbpf: Add support to create tracing multi link Jiri Olsa
2026-03-04 23:02 ` bot+bpf-ci
2026-03-05 14:02 ` Jiri Olsa
2026-03-05 6:59 ` Leon Hwang
2026-03-05 14:02 ` Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 16/23] selftests/bpf: Add tracing multi skel/pattern/ids attach tests Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 17/23] selftests/bpf: Add tracing multi skel/pattern/ids module " Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 18/23] selftests/bpf: Add tracing multi intersect tests Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 19/23] selftests/bpf: Add tracing multi cookies test Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 20/23] selftests/bpf: Add tracing multi session test Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 21/23] selftests/bpf: Add tracing multi attach fails test Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 22/23] selftests/bpf: Add tracing multi attach benchmark test Jiri Olsa
2026-03-05 7:30 ` Leon Hwang
2026-03-05 14:01 ` Jiri Olsa
2026-03-04 22:21 ` [PATCHv2 bpf-next 23/23] selftests/bpf: Add tracing multi rollback tests Jiri Olsa
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