From: Paul Chaignon <paul.chaignon@gmail.com>
To: Sun Jian <sun.jian.kdev@gmail.com>
Cc: andrii@kernel.org, eddyz87@gmail.com, shuah@kernel.org,
ast@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev,
song@kernel.org, yonghong.song@linux.dev,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me,
haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] selftests/bpf: trampoline_count: use dedicated target function
Date: Tue, 17 Mar 2026 01:12:00 +0100 [thread overview]
Message-ID: <abicUI4YQ5KkQ_Ro@mail.gmail.com> (raw)
In-Reply-To: <20260315054227.118344-1-sun.jian.kdev@gmail.com>
On Sun, Mar 15, 2026 at 01:42:27PM +0800, Sun Jian wrote:
> trampoline_count fills all trampoline attachment slots for a single
> target function and verifies that one extra attach fails with -E2BIG.
>
> It currently targets bpf_modify_return_test, which is also used by
> modify_return and get_func_ip_test. When those tests run in parallel,
> they can contend for the same per-function trampoline quota and
> cause unexpected attach failures. This issue is currently masked by
> harness serialization.
>
> Add a dedicated bpf_trampoline_count_test target and switch
> trampoline_count to use it. This keeps the test semantics unchanged
> while isolating it from other modify_return-based selftests, so it no
> longer needs to run in serial mode. Remove the TODO comment as
> well.
>
> Tested:
> ./test_progs -t trampoline_count -vv
> ./test_progs -t modify_return -vv
> ./test_progs -t get_func_ip_test -vv
> ./test_progs -j$(nproc) -t trampoline_count -vv
> ./test_progs -j$(nproc) -t
> trampoline_count,modify_return,get_func_ip_test -vv
I was able to reproduce the issue here then validate the fix. I however
had to include several more tests that use bpf_modify_return_test
(get_func_args_test, kprobe_multi_test, missed, and bpf_cookie) before
I could reliably reproduce (in a loop that runs until it fails with
an unexpected E2BIG).
Tested-by: Paul Chaignon <paul.chaignon@gmail.com>
[...]
next prev parent reply other threads:[~2026-03-17 0:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-15 5:42 [PATCH] selftests/bpf: trampoline_count: use dedicated target function Sun Jian
2026-03-17 0:12 ` Paul Chaignon [this message]
2026-03-17 1:02 ` [PATCH v2] " Sun Jian
2026-03-17 10:54 ` Paul Chaignon
2026-03-19 0:14 ` [PATCH] " Alexei Starovoitov
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