linux-kernel - Re: [PATCH sched_ext/for-6.13-fixes] sched_ext: Fix dsq_local

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Message-ID: <QHB1r-3fBPQIaDS8iz26J-zoMbn3O6VLlwlZP1NQdkMzlQTsCX_xrfTPBoGt6SQOGgtg6vN7aXles4CndepTvjIVQ7bVXDBrvPaiRH5R8tc=@pm.me>
Date: Wed, 15 Jan 2025 23:50:37 +0000
From: Ihor Solodrai <ihor.solodrai@...me>
To: Tejun Heo <tj@...nel.org>
Cc: sched-ext@...a.com, kernel-team@...a.com, linux-kernel@...r.kernel.org, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH sched_ext/for-6.13-fixes] sched_ext: Fix dsq_local_on selftest

On Tuesday, December 24th, 2024 at 4:09 PM, Tejun Heo <tj@...nel.org> wrote:

> 
> 
> The dsp_local_on selftest expects the scheduler to fail by trying to
> schedule an e.g. CPU-affine task to the wrong CPU. However, this isn't
> guaranteed to happen in the 1 second window that the test is running.
> Besides, it's odd to have this particular exception path tested when there
> are no other tests that verify that the interface is working at all - e.g.
> the test would pass if dsp_local_on interface is completely broken and fails
> on any attempt.
> 
> Flip the test so that it verifies that the feature works. While at it, fix a
> typo in the info message.
> 
> Signed-off-by: Tejun Heo tj@...nel.org
> 
> Reported-by: Ihor Solodrai ihor.solodrai@...me
> 
> Link: http://lkml.kernel.org/r/Z1n9v7Z6iNJ-wKmq@slm.duckdns.org
> ---
> tools/testing/selftests/sched_ext/dsp_local_on.bpf.c | 5 ++++-
> tools/testing/selftests/sched_ext/dsp_local_on.c | 5 +++--
> 2 files changed, 7 insertions(+), 3 deletions(-)

Hi Tejun.

I've tried running sched_ext selftests on BPF CI today, applying a set
of patches from sched_ext/for-6.13-fixes, including this one.

You can see the list of patches I added here:
https://github.com/kernel-patches/vmtest/pull/332/files

With that, dsq_local_on has failed on x86_64 (llvm-18), although it
passed with other configurations:
https://github.com/kernel-patches/vmtest/actions/runs/12798804552/job/35683769806

Here is a piece of log that appears to be relevant:

    2025-01-15T23:28:55.8238375Z [    5.334631] sched_ext: BPF scheduler "dsp_local_on" disabled (runtime error)
    2025-01-15T23:28:55.8243034Z [    5.335420] sched_ext: dsp_local_on: SCX_DSQ_LOCAL[_ON] verdict target cpu 1 not allowed for kworker/u8:1[33]
    2025-01-15T23:28:55.8246187Z [    5.336139]    dispatch_to_local_dsq+0x13e/0x1f0
    2025-01-15T23:28:55.8249296Z [    5.336474]    flush_dispatch_buf+0x13d/0x170
    2025-01-15T23:28:55.8252083Z [    5.336793]    balance_scx+0x225/0x3e0
    2025-01-15T23:28:55.8254695Z [    5.337065]    __schedule+0x406/0xe80
    2025-01-15T23:28:55.8257121Z [    5.337330]    schedule+0x41/0xb0
    2025-01-15T23:28:55.8260146Z [    5.337574]    schedule_timeout+0xe5/0x160
    2025-01-15T23:28:55.8263080Z [    5.337875]    rcu_tasks_kthread+0xb1/0xc0
    2025-01-15T23:28:55.8265477Z [    5.338169]    kthread+0xfa/0x120
    2025-01-15T23:28:55.8268202Z [    5.338410]    ret_from_fork+0x37/0x50
    2025-01-15T23:28:55.8271272Z [    5.338690]    ret_from_fork_asm+0x1a/0x30
    2025-01-15T23:28:56.7349562Z ERR: dsp_local_on.c:39
    2025-01-15T23:28:56.7350182Z Expected skel->data->uei.kind == EXIT_KIND(SCX_EXIT_UNREG) (1024 == 64)

Could you please take a look?

Thank you.

> 
> [...]