Re: linux-6.2-rc4+ hangs on poweroff/reboot: Bisected

[Linux regression tracking (Thorsten Leemhuis)]

On 08.02.23 09:48, Chris Clayton wrote:
> 
> I'm assuming  that we are not going to see a fix for this regression before 6.2 is released.

Yeah, looks like it. That's unfortunate, but happens. But there is still
time to fix it and there is one thing I wonder:

Did any of the nouveau developers look at the netconsole captures Chris
posted more than a week ago to check if they somehow help to track down
the root of this problem?

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.

> Consequently, I've
> implemented a (very simple) workaround. All that happens is that in the (sysv) init script that starts and stops SDDM,
> the nouveau module is removed once SDDM is stopped. With that in place, my system no longer freezes on reboot or poweroff.
> 
> Let me know if I can provide any additional diagnostics although, with the problem seemingly occurring so late in the
> shutdown process, I may need help on how to go about capturing.
> 
> Chris
> 
> On 02/02/2023 20:45, Chris Clayton wrote:
>>
>>
>> On 01/02/2023 13:51, Chris Clayton wrote:
>>>
>>>
>>> On 30/01/2023 23:27, Ben Skeggs wrote:
>>>> On Tue, 31 Jan 2023 at 09:09, Chris Clayton <chris2553@xxxxxxxxxxxxxx> wrote:
>>>>>
>>>>> Hi again.
>>>>>
>>>>> On 30/01/2023 20:19, Chris Clayton wrote:
>>>>>> Thanks, Ben.
>>>>>
>>>>> <snip>
>>>>>
>>>>>>> Hey,
>>>>>>>
>>>>>>> This is a complete shot-in-the-dark, as I don't see this behaviour on
>>>>>>> *any* of my boards.  Could you try the attached patch please?
>>>>>>
>>>>>> Unfortunately, the patch made no difference.
>>>>>>
>>>>>> I've been looking at how the graphics on my laptop is set up, and have a bit of a worry about whether the firmware might
>>>>>> be playing a part in this problem. In order to offload video decoding to the NVidia TU117 GPU, it seems the scrubber
>>>>>> firmware must be available, but as far as I know,that has not been released by NVidia. To get it to work, I followed
>>>>>> what ubuntu have done and the scrubber in /lib/firmware/nvidia/tu117/nvdec/ is a symlink to
>>>>>> ../../tu116/nvdev/scrubber.bin. That, of course, means that some of the firmware loaded is for a different card is being
>>>>>> loaded. I note that processing related to firmware is being changed in the patch. Might my set up be at the root of my
>>>>>> problem?
>>>>>>
>>>>>> I'll have a fiddle an see what I can work out.
>>>>>>
>>>>>> Chris
>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Ben.
>>>>>>>
>>>>>>>>
>>>>>
>>>>> Well, my fiddling has got my system rebooting and shutting down successfully again. I found that if I delete the symlink
>>>>> to the scrubber firmware, reboot and shutdown work again. There are however, a number of other files in the tu117
>>>>> firmware directory tree that that are symlinks to actual files in its tu116 counterpart. So I deleted all of those too.
>>>>> Unfortunately, the absence of one or more of those symlinks causes Xorg to fail to start. I've reinstated all the links
>>>>> except scrubber and I now have a system that works as it did until I tried to run a kernel that includes the bad commit
>>>>> I identified in my bisection. That includes offloading video decoding to the NVidia card, so what ever I read that said
>>>>> the scrubber firmware was needed seems to have been wrong. I get a new message that (nouveau 0000:01:00.0: fb: VPR
>>>>> locked, but no scrubber binary!), but, hey, we can't have everything.
>>>>>
>>>>> If you still want to get to the bottom of this, let me know what you need me to provide and I'll do my best. I suspect
>>>>> you might want to because there will a n awful lot of Ubuntu-based systems out there with that scrubber.bin symlink in
>>>>> place. On the other hand,m it could but quite a while before ubuntu are deploying 6.2 or later kernels.
>>>> The symlinks are correct - whole groups of GPUs share the same FW, and
>>>> we use symlinks in linux-firmware to represent this.
>>>>
>>>> I don't really have any ideas how/why this patch causes issues with
>>>> shutdown - it's a path that only gets executed during initialisation.
>>>> Can you try and capture the kernel log during shutdown ("dmesg -w"
>>>> over ssh? netconsole?), and see if there's any relevant messages
>>>> providing a hint at what's going on?  Alternatively, you could try
>>>> unloading the module (you will have to stop X/wayland/gdm/etc/etc
>>>> first) and seeing if that hangs too.
>>>>
>>>> Ben.
>>>
>>> Sorry for the delay - I've been learning about netconsole and netcat. However, I had no success with ssh and netconsole
>>> produced a log with nothing unusual in it.
>>>
>>> Simply stopping Xorg and removing the nouveau module succeeds.
>>>
>>> So, I rebuilt rc6+ after a pull from linus' tree this morning and set the nouveau debug level to 7. I then booted to a
>>> console before doing a reboot (with Ctl+Alt+Del). As expected the machine locked up just before it would ordinarily
>>> restart. The last few lines on the console might be helpful:
>>>
>>> ...
>>> nouveau 0000:01:00:0  fifo: preinit running...
>>> nouveau 0000:01:00:0  fifo: preinit completed in 4us
>>> nouveau 0000:01:00:0  gr: preinit running...
>>> nouveau 0000:01:00:0  gr: preinit completed in 0us
>>> nouveau 0000:01:00:0  nvdec0: preinit running...
>>> nouveau 0000:01:00:0  nvdec0: preinit completed in 0us
>>> nouveau 0000:01:00:0  nvdec0: preinit running...
>>> nouveau 0000:01:00:0  nvdec0: preinit completed in 0us
>>> nouveau 0000:01:00:0  sec2: preinit running...
>>> nouveau 0000:01:00:0  sec2: preinit completed in 0us
>>> nouveau 0000:01:00:0  fb:.VPR locked, running scrubber binary
>>>
>>> These messages appear after the "sd 4:0:0:0 [sda] Stopping disk" I reported in my initial email.
>>>
>>> After the "running scrubber" line appears the machine is locked and I have to hold down the power button to recover. I
>>> get the same outcome from running "halt -dip", "poweroff -di" and "shutdown -h -P now". I guess it's no surprise that
>>> all three result in the same outcome because invocations halt, poweroff and reboot (without the -f argument)from a
>>> runlevel other than 0 resukt in shutdown being run. switching to runlevel 0 with "telenit 0" results in the same
>>> messages from nouveau followed by the lockup.
>>>
>>> Let me know if you need any additional diagnostics.
>>>
>>> Chris
>>>
>>
>> I've done some more investigation and found that I hadn't done sufficient amemdment the scripts run at shutdown to
>> prevent the network being shutdown. I've now got netconsole captures for 6.2.0-rc6+
>> (9f266ccaa2f5228bfe67ad58a94ca4e0109b954a) and, for comparison, 6.1.9. These two logs are attached.
>>
>> Chris
>>
>>>>
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Chris
>>>>>
>>>>> <snip>
> 
>