linux-kernel - Re: [PATCH bpf v3 2/2] selftests/bpf: Add test for unpinning htab with internal timer struct

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Message-ID: <2cf1e3614241abf51a0db5ac435b2f673895a607.camel@linux.dev>
Date: Sat, 11 Oct 2025 23:09:40 +0800
From: KaFai Wan <kafai.wan@...ux.dev>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
 <daniel@...earbox.net>,  Andrii Nakryiko <andrii@...nel.org>, Martin KaFai
 Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>, Song Liu
 <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, John Fastabend
 <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, Stanislav
 Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
 <jolsa@...nel.org>,  Shuah Khan <shuah@...nel.org>, Toke
 Høiland-Jørgensen <toke@...hat.com>, LKML
 <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>, "open
 list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH bpf v3 2/2] selftests/bpf: Add test for unpinning htab
 with internal timer struct

On Fri, 2025-10-10 at 10:28 -0700, Alexei Starovoitov wrote:
> On Wed, Oct 8, 2025 at 3:27 AM KaFai Wan <kafai.wan@...ux.dev> wrote:
> > 
> > Add test to verify that unpinning hash tables containing internal timer
> > structures does not trigger context warnings.
> > 
> > Each subtest (timer_prealloc and timer_no_prealloc) can trigger the
> > context warning when unpinning, but the warning cannot be triggered
> > twice within a short time interval (a HZ), which is expected behavior.
> 
> It was difficult to decipher the above paragraph.
> I think you're referring to throttling logic in __might_resched().
> 
> I kept it as-is while applying, but in the future either skip
> such low level implementation detail or expand it.
> Here you could have said that the error is printed by __might_resched()
> which prints it once a HZ.

OK, I understand. Thanks for your feedback and guidance.

-- 
Thanks,
KaFai