Message-ID: <31e7fbbb-3f66-0b2b-804d-1fb61cc62a59@leemhuis.info>
Date:   Mon, 5 Jun 2023 13:35:15 +0200
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Janne Grunau <j@...nau.net>, maarten.lankhorst@...ux.intel.com,
        mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
        daniel@...ll.ch, neil.armstrong@...aro.org, tony.luck@...el.com,
        keescook@...omium.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, gpiccoli@...lia.com,
        linux-hardening@...r.kernel.org, laurentiu.palcu@....nxp.com,
        regressions@...ts.linux.dev, zongmin zhou <zhouzongmin@...inos.cn>
Subject: Re: [PATCH] drm/probe_helper: fix the warning reported when calling
 drm_kms_helper_poll_disable during suspend

On 17.05.23 17:15, Linux regression tracking (Thorsten Leemhuis) wrote:
> Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting
> for once, to make this easily accessible to everyone.
> 
> Dmitry, was any progress made to address this regression? Doesn't look
> like it, but I strongly suspect I'm missing something,

FWIW, I'm dropping this from the regression tracking. It might be still
around, but it's a warning and nothing that really breaks things afaics.

Please holler if I got this wrong and think it's something that needs to
be fixed to ensure the "no regressions" rule is adhered.

#regzbot inconclusive: a warn() without serious impact, see discussion
#regzbot ignore-activity

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
If I did something stupid, please tell me, as explained on that page.

> as I'm not really
> sure if I properly understood this thread. It sounded a bit like
> a4e771729a51 should be reverted for now until all
> drm_kms_helper_poll_disable() calls have been verified. Is that right?
> Or did somebody already verify and fix all of them with bugs?
>
> On 28.04.23 03:17, zongmin zhou wrote:
>> On Wed, 2023-04-26 at 16:10 +0300, Dmitry Baryshkov wrote:
>>> On Wed, 26 Apr 2023 at 12:09, zongmin zhou <zhouzongmin@...inos.cn>
>>> wrote:
>>>> On Sun, 2023-04-23 at 22:51 +0200, Janne Grunau wrote:
>>>>> On 2023-04-20 23:07:01 +0300, Dmitry Baryshkov wrote:
>>>>>> On Thu, 20 Apr 2023 at 23:01, Janne Grunau <j@...nau.net>
>>>>>> wrote:
>>>>>>>
>>>>>>> On 2023-03-28 10:31:29 +0800, Zongmin Zhou wrote:
>>>>>>>> When drivers call drm_kms_helper_poll_disable from
>>>>>>>> their device suspend implementation without enabled output
>>>>>>>> polling before,
>>>>>>>> following warning will be reported,due to work->func not be
>>>>>>>> initialized:
>>>>>>>
>>>>>>> we see the same warning with the wpork in progress kms driver
>>>>>>> for
>>>>>>> apple
>>>>>>> silicon SoCs. The connectors do not need to polled so the
>>>>>>> driver
>>>>>>> never
>>>>>>> calls drm_kms_helper_poll_init().
>>>>>>>
>>>>>>>> [   55.141361] WARNING: CPU: 3 PID: 372 at
>>>>>>>> kernel/workqueue.c:3066 __flush_work+0x22f/0x240
>>>>>>>> [   55.141382] Modules linked in: nls_iso8859_1
>>>>>>>> snd_hda_codec_generic ledtrig_audio snd_hda_intel
>>>>>>>> snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec
>>>>>>>> snd_hda_core
>>>>>>>> snd_hwdep snd_pcm snd_seq_midi snd_seq_midi_event
>>>>>>>> snd_rawmidi
>>>>>>>> snd_seq intel_rapl_msr intel_rapl_common bochs
>>>>>>>> drm_vram_helper
>>>>>>>> drm_ttm_helper snd_seq_device nfit ttm crct10dif_pclmul
>>>>>>>> snd_timer ghash_clmulni_intel binfmt_misc sha512_ssse3
>>>>>>>> aesni_intel drm_kms_helper joydev input_leds syscopyarea
>>>>>>>> crypto_simd snd cryptd sysfillrect sysimgblt mac_hid
>>>>>>>> serio_raw
>>>>>>>> soundcore qemu_fw_cfg sch_fq_codel msr parport_pc ppdev lp
>>>>>>>> parport drm ramoops reed_solomon pstore_blk pstore_zone
>>>>>>>> efi_pstore virtio_rng ip_tables x_tables autofs4
>>>>>>>> hid_generic
>>>>>>>> usbhid hid ahci virtio_net i2c_i801 crc32_pclmul psmouse
>>>>>>>> virtio_scsi libahci i2c_smbus lpc_ich xhci_pci net_failover
>>>>>>>> virtio_blk xhci_pci_renesas failover
>>>>>>>> [   55.141430] CPU: 3 PID: 372 Comm: kworker/u16:9 Not
>>>>>>>> tainted
>>>>>>>> 6.2.0-rc6+ #16
>>>>>>>> [   55.141433] Hardware name: QEMU Standard PC (Q35 + ICH9,
>>>>>>>> 2009), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org
>>>>>>>> 04/01/2014
>>>>>>>> [   55.141435] Workqueue: events_unbound async_run_entry_fn
>>>>>>>> [   55.141441] RIP: 0010:__flush_work+0x22f/0x240
>>>>>>>> [   55.141444] Code: 8b 43 28 48 8b 53 30 89 c1 e9 f9 fe ff
>>>>>>>> ff
>>>>>>>> 4c 89 f7 e8 b5 95 d9 00 e8 00 53 08 00 45 31 ff e9 11 ff ff
>>>>>>>> ff
>>>>>>>> 0f 0b e9 0a ff ff ff <0f> 0b 45 31 ff e9 00 ff ff ff e8 e2
>>>>>>>> 54
>>>>>>>> d8 00 66 90 90 90 90 90 90
>>>>>>>> [   55.141446] RSP: 0018:ff59221940833c18 EFLAGS: 00010246
>>>>>>>> [   55.141449] RAX: 0000000000000000 RBX: 0000000000000000
>>>>>>>> RCX:
>>>>>>>> ffffffff9b72bcbe
>>>>>>>> [   55.141450] RDX: 0000000000000001 RSI: 0000000000000001
>>>>>>>> RDI:
>>>>>>>> ff3ea01e4265e330
>>>>>>>> [   55.141451] RBP: ff59221940833c90 R08: 0000000000000000
>>>>>>>> R09:
>>>>>>>> 8080808080808080
>>>>>>>> [   55.141453] R10: ff3ea01e42b3caf4 R11: 000000000000000f
>>>>>>>> R12:
>>>>>>>> ff3ea01e4265e330
>>>>>>>> [   55.141454] R13: 0000000000000001 R14: ff3ea01e505e5e80
>>>>>>>> R15:
>>>>>>>> 0000000000000001
>>>>>>>> [   55.141455] FS:  0000000000000000(0000)
>>>>>>>> GS:ff3ea01fb7cc0000(0000) knlGS:0000000000000000
>>>>>>>> [   55.141456] CS:  0010 DS: 0000 ES: 0000 CR0:
>>>>>>>> 0000000080050033
>>>>>>>> [   55.141458] CR2: 0000563543ad1546 CR3: 000000010ee82005
>>>>>>>> CR4:
>>>>>>>> 0000000000771ee0
>>>>>>>> [   55.141464] DR0: 0000000000000000 DR1: 0000000000000000
>>>>>>>> DR2:
>>>>>>>> 0000000000000000
>>>>>>>> [   55.141465] DR3: 0000000000000000 DR6: 00000000fffe0ff0
>>>>>>>> DR7:
>>>>>>>> 0000000000000400
>>>>>>>> [   55.141466] PKRU: 55555554
>>>>>>>> [   55.141467] Call Trace:
>>>>>>>> [   55.141469]  <TASK>
>>>>>>>> [   55.141472]  ? pcie_wait_cmd+0xdf/0x220
>>>>>>>> [   55.141478]  ? mptcp_seq_show+0xe0/0x180
>>>>>>>> [   55.141484]  __cancel_work_timer+0x124/0x1b0
>>>>>>>> [   55.141487]  cancel_delayed_work_sync+0x17/0x20
>>>>>>>> [   55.141490]  drm_kms_helper_poll_disable+0x26/0x40
>>>>>>>> [drm_kms_helper]
>>>>>>>> [   55.141516]  drm_mode_config_helper_suspend+0x25/0x90
>>>>>>>> [drm_kms_helper]
>>>>>>>> [   55.141531]  ? __pm_runtime_resume+0x64/0x90
>>>>>>>> [   55.141536]  bochs_pm_suspend+0x16/0x20 [bochs]
>>>>>>>> [   55.141540]  pci_pm_suspend+0x8b/0x1b0
>>>>>>>> [   55.141545]  ? __pfx_pci_pm_suspend+0x10/0x10
>>>>>>>> [   55.141547]  dpm_run_callback+0x4c/0x160
>>>>>>>> [   55.141550]  __device_suspend+0x14c/0x4c0
>>>>>>>> [   55.141553]  async_suspend+0x24/0xa0
>>>>>>>> [   55.141555]  async_run_entry_fn+0x34/0x120
>>>>>>>> [   55.141557]  process_one_work+0x21a/0x3f0
>>>>>>>> [   55.141560]  worker_thread+0x4e/0x3c0
>>>>>>>> [   55.141563]  ? __pfx_worker_thread+0x10/0x10
>>>>>>>> [   55.141565]  kthread+0xf2/0x120
>>>>>>>> [   55.141568]  ? __pfx_kthread+0x10/0x10
>>>>>>>> [   55.141570]  ret_from_fork+0x29/0x50
>>>>>>>> [   55.141575]  </TASK>
>>>>>>>> [   55.141575] ---[ end trace 0000000000000000 ]---
>>>>>>>>
>>>>>>>> Fixes: a4e771729a51 ("drm/probe_helper: sort out
>>>>>>>> poll_running
>>>>>>>> vs poll_enabled")
>>>>>>>> Signed-off-by: Zongmin Zhou<zhouzongmin@...inos.cn>
>>>>>>>> ---
>>>>>>>>  drivers/gpu/drm/drm_probe_helper.c | 3 ++-
>>>>>>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/drm_probe_helper.c
>>>>>>>> b/drivers/gpu/drm/drm_probe_helper.c
>>>>>>>> index 8127be134c39..ac72b18e2257 100644
>>>>>>>> --- a/drivers/gpu/drm/drm_probe_helper.c
>>>>>>>> +++ b/drivers/gpu/drm/drm_probe_helper.c
>>>>>>>> @@ -855,7 +855,8 @@ void drm_kms_helper_poll_disable(struct
>>>>>>>> drm_device *dev)
>>>>>>>>       if (dev->mode_config.poll_running)
>>>>>>>>               drm_kms_helper_disable_hpd(dev);
>>>>>>>>
>>>>>>>> -     cancel_delayed_work_sync(&dev-
>>>>>>>>> mode_config.output_poll_work);
>>>>>>>> +     if (dev->mode_config.poll_enabled)
>>>>>>>> +             cancel_delayed_work_sync(&dev-
>>>>>>>>> mode_config.output_poll_work);
>>>>>>>
>>>>>>> Checking for dev->mode_config.poll_enabled at the start of
>>>>>>> the
>>>>>>> function
>>>>>>> and return early if it is not true looks more in style with
>>>>>>> the
>>>>>>> rest of
>>>>>>> drm_probe_helper.c.
>>>>>>
>>>>>> I think it is an error to call drm_kms_helper_poll_disable() if
>>>>>> polling was not initialized. So, in my opinion the fix should
>>>>>> go to
>>>>>> the drm_mode_config_helper_suspend() / _resume() instead.
>>>>>> Please
>>>>>> add a
>>>>>> guard there using dev->mode_config.poll_enabled.
>>>>>
>>>>> While I tend to agree to the sentiment I do not think this is the
>>>>> correct fix in this situation. drm_kms_helper_poll_disable had
>>>>> the
>>>>> check since at least 2014. a4e771729a51 is a regression. If we
>>>>> want
>>>>> to
>>>>> change the behavior it should be done explicitly and after
>>>>> verifying
>>>>> all
>>>>> drm_kms_helper_poll_disable() calls.
>>>>>
>>>>> #regzbot ^introduced a4e771729a51
>>>>>
>>>>> ciao
>>>>> Janne
>>>>
>>>> Dear Janne:
>>>>
>>>> I agree with you like I mentioned on last letter.
>>>> Thanks for your time.
>>>>
>>>>
>>>> Dear Dmitry:
>>>>
>>>> Is there anything else I can do?
>>>> Looking forward to your reply.
>>>
>>> If it is a common consensus, I'm fine with your approach.
>>>
>> Dear Dmitry:
>>
>> Ok.Thanks for your reply.
>>
>> Best regards!
>>
>>

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