[Regression] CPU stalls and eventually causes a complete system freeze with 6.0.3 due to "video/aperture: Disable and unregister sysfb devices via aperture helpers"

[Thomas Zimmermann]

Hi Andreas

Am 24.10.22 um 18:19 schrieb Andreas Thalhammer:
> Am 24.10.22 um 13:31 schrieb Thomas Zimmermann:
>> Hi
>>
>> Am 24.10.22 um 13:27 schrieb Greg KH:
>>> On Mon, Oct 24, 2022 at 12:41:43PM +0200, Thorsten Leemhuis wrote:
>>>> Hi! Thx for the reply.
>>>>
>>>> On 24.10.22 12:26, Thomas Zimmermann wrote:
>>>>> Am 23.10.22 um 10:04 schrieb Thorsten Leemhuis:
>>>>>>
>>>>>> I noticed a regression report in bugzilla.kernel.org. As many (most?)
>>>>>> kernel developer don't keep an eye on it, I decided to forward it by
>>>>>> mail. Quoting from
>>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=216616  :
>>>>>>
>>>>>>>    Andreas 2022-10-22 14:25:32 UTC
>>>>>>>
>>>>>>> Created attachment 303074 [details]
>>>>>>> dmesg
>>>>>
>>>>> I've looked at the kernel log and found that simpledrm has been loaded
>>>>> *after* amdgpu, which should never happen. The problematic patch has
>>>>> been taken from a long list of refactoring work on this code. No 
>>>>> wonder
>>>>> that it doesn't work as expected.
>>>>>
>>>>> Please cherry-pick commit 9d69ef183815 ("fbdev/core: Remove
>>>>> remove_conflicting_pci_framebuffers()") into the 6.0 stable branch and
>>>>> report on the results. It should fix the problem.
>>>>
>>>> Greg, is that enough for you to pick this up? Or do you want Andreas to
>>>> test first if it really fixes the reported problem?
>>>
>>> This should be good enough.  If this does NOT fix the issue, please let
>>> me know.
>>
>> Thanks a lot. I think I can provided a dedicated fix if the proposed
>> commit doesn't work.
>>
>> Best regards
>> Thomas
>>
>>>
>>> thanks,
>>>
>>> greg k-h
>>
> 
> Thanks... In short: the additional patch did NOT fix the problem.

Yeah, it's also part of a larger changeset. But I wouldn't want to 
backport all those changes either.

Attached is a simple patch for linux-stable that adds the necessary fix. 
If this still doesn't work, we should probably revert the problematic patch.

Please test the patch and let me know if it works.

Best regards
Thomas

> 
> I don't use git and I don't know how to /cherry-pick commit/
> 9d69ef183815, but I found the patch here:
> https://patchwork.freedesktop.org/patch/494609/
> 
> I hope that's the right one. I reintegrated
> v2-07-11-video-aperture-Disable-and-unregister-sysfb-devices-via-aperture-helpers.patch
> and also applied
> v2-04-11-fbdev-core-Remove-remove_conflicting_pci_framebuffers.patch,
> did a "make mrproper" and thereafter compiled a clean new 6.0.3 kernel
> (same .config).
> 
> Now the system doesn't even boot to a console. The first boot got me to
> a rcu_shed stall on CPUs/tasks, same as above, but this time with:
> Workqueue: btrfs-cache btrfs_work_helper
> 
> I booted a second time with the same kernel, and it got stuck after
> mounting the root btrfs filesystem (what looked like a total freeze, but
> when it didn't show a rcu_stall message after ~2 min I got impatient and
> wanted to see if I had just busted my root filesystem...)
> 
> I booted 6.0.2 and everything is fine. (I'm very glad! I definitely
> should update my backup right away!)
> 
> I will try 6.1-rc1 next, bear with...
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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