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Message-ID: <48deb3fa-1784-a08d-aa8c-93ccf63a4aba@leemhuis.info>
Date:   Wed, 17 May 2023 17:15:43 +0200
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Subject: Re: [PATCH] drm/probe_helper: fix the warning reported when calling
 drm_kms_helper_poll_disable during suspend
Content-Language: en-US, de-DE
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc:     Janne Grunau <j@jannau.net>, maarten.lankhorst@linux.intel.com,
        mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com,
        daniel@ffwll.ch, neil.armstrong@linaro.org, tony.luck@intel.com,
        keescook@chromium.org, linux-kernel@vger.kernel.org,
        dri-devel@lists.freedesktop.org, gpiccoli@igalia.com,
        linux-hardening@vger.kernel.org, laurentiu.palcu@oss.nxp.com,
        regressions@lists.linux.dev, zongmin zhou <zhouzongmin@kylinos.cn>
References: <20230328023129.3596968-1-zhouzongmin@kylinos.cn>
 <20230420200148.GD3280@jannau.net>
 <CAA8EJpoK3yv3E==bJuDoQhsW2Q1LdqKakJgdZx6S=ec-CvyGyw@mail.gmail.com>
 <1682386644754589.204.seg@mailgw>
 <1186d62a5fe7f2aa6e06f06a3dc7605c0072f1eb.camel@kylinos.cn>
 <CAA8EJppmUtuhAF+VHPh3Q8tNYp1m4T6P7dZ0wYZ8Vzwo0DF6cg@mail.gmail.com>
 <6599319fea8ed1e3d6968e5b986661f0cf175902.camel@kylinos.cn>
From:   "Linux regression tracking (Thorsten Leemhuis)" 
        <regressions@leemhuis.info>
Reply-To: Linux regressions mailing list <regressions@lists.linux.dev>
In-Reply-To: <6599319fea8ed1e3d6968e5b986661f0cf175902.camel@kylinos.cn>
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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, 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?

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.

#regzbot poke

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@kylinos.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@jannau.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@kylinos.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!
> 
>