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

[Chris Clayton <chris2553@googlemail.com>]

On 30/01/2023 23:27, Ben Skeggs wrote:
> On Tue, 31 Jan 2023 at 09:09, Chris Clayton <chris2553@googlemail.com> 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

> 
>>
>> Thanks,
>>
>> Chris
>>
>> <snip>