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

From: Chris Clayton
Date: Sat Feb 18 2023 - 10:20:10 EST



On 18/02/2023 12:25, Karol Herbst wrote:
> On Sat, Feb 18, 2023 at 1:22 PM Chris Clayton <chris2553@xxxxxxxxxxxxxx> wrote:
>>
>>
>>
>> On 15/02/2023 11:09, Karol Herbst wrote:
>>> On Wed, Feb 15, 2023 at 11:36 AM Linux regression tracking #update
>>> (Thorsten Leemhuis) <regressions@xxxxxxxxxxxxx> wrote:
>>>>
>>>> On 13.02.23 10:14, Chris Clayton wrote:
>>>>> On 13/02/2023 02:57, Dave Airlie wrote:
>>>>>> On Sun, 12 Feb 2023 at 00:43, Chris Clayton <chris2553@xxxxxxxxxxxxxx> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 10/02/2023 19:33, Linux regression tracking (Thorsten Leemhuis) wrote:
>>>>>>>> On 10.02.23 20:01, Karol Herbst wrote:
>>>>>>>>> On Fri, Feb 10, 2023 at 7:35 PM Linux regression tracking (Thorsten
>>>>>>>>> Leemhuis) <regressions@xxxxxxxxxxxxx> wrote:
>>>>>>>>>>
>>>>>>>>>> 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?
>>>>>>>>>
>>>>>>>>> I did now and I can't spot anything. I think at this point it would
>>>>>>>>> make sense to dump the active tasks/threads via sqsrq keys to see if
>>>>>>>>> any is in a weird state preventing the machine from shutting down.
>>>>>>>>
>>>>>>>> Many thx for looking into it!
>>>>>>>
>>>>>>> Yes, thanks Karol.
>>>>>>>
>>>>>>> Attached is the output from dmesg when this block of code:
>>>>>>>
>>>>>>> /bin/mount /dev/sda7 /mnt/sda7
>>>>>>> /bin/mountpoint /proc || /bin/mount /proc
>>>>>>> /bin/dmesg -w > /mnt/sda7/sysrq.dmesg.log &
>>>>>>> /bin/echo t > /proc/sysrq-trigger
>>>>>>> /bin/sleep 1
>>>>>>> /bin/sync
>>>>>>> /bin/sleep 1
>>>>>>> kill $(pidof dmesg)
>>>>>>> /bin/umount /mnt/sda7
>>>>>>>
>>>>>>> is executed immediately before /sbin/reboot is called as the final step of rebooting my system.
>>>>>>>
>>>>>>> I hope this is what you were looking for, but if not, please let me know what you need
>>>>>
>>>>> Thanks Dave. [...]
>>>> FWIW, in case anyone strands here in the archives: the msg was
>>>> truncated. The full post can be found in a new thread:
>>>>
>>>> https://lore.kernel.org/lkml/e0b80506-b3cf-315b-4327-1b988d86031e@xxxxxxxxxxxxxx/
>>>>
>>>> Sadly it seems the info "With runpm=0, both reboot and poweroff work on
>>>> my laptop." didn't bring us much further to a solution. :-/ I don't
>>>> really like it, but for regression tracking I'm now putting this on the
>>>> back-burner, as a fix is not in sight.
>>>>
>>>> #regzbot monitor:
>>>> https://lore.kernel.org/lkml/e0b80506-b3cf-315b-4327-1b988d86031e@xxxxxxxxxxxxxx/
>>>> #regzbot backburner: hard to debug and apparently rare
>>>> #regzbot ignore-activity
>>>>
>>>
>>> yeah.. this bug looks a little annoying. Sadly the only Turing based
>>> laptop I got doesn't work on Nouveau because of firmware related
>>> issues and we probably need to get updated ones from Nvidia here :(
>>>
>>> But it's a bit weird that the kernel doesn't shutdown, because I don't
>>> see anything in the logs which would prevent that from happening.
>>> Unless it's waiting on one of the tasks to complete, but none of them
>>> looked in any way nouveau related.
>>>
>>> If somebody else has any fancy kernel debugging tips here to figure
>>> out why it hangs, that would be very helpful...
>>>
>>
>> I think I've figured this out. It's to do with how my system is configured. I do have an initrd, but the only thing on
>> it is the cpu microcode which, it is recommended, should be loaded early. The absence of the NVidia firmare from an
>> initrd doesn't matter because the drivers for the hardware that need to load firmware are all built as modules, So, by
>> the time the devices are configured via udev, the root partition is mounted and the drivers can get at the firmware.
>>
>> I've found, by turning on nouveau debug and taking a video of the screen as the system shuts down, that nouveau seems to
>> be trying to run the scrubber very very late in the shutdown process. The problem is that by this time, I think the root
>> partition, and thus the scrubber binary, have become inaccessible.
>>
>> I seem to have two choices - either make the firmware accessible on an initrd or unload the module in a shutdown script
>> before the scrubber binary becomes inaccessible. The latter of these is the workaround I have implemented whilst the
>> problem I reported has been under investigation. For simplicity, I think I'll promote my workaround to being the
>> permanent solution.
>>
>> So, apologies (and thanks) to everyone whose time I have taken up with this non-bug.
>>
>
> Well.. nouveau shouldn't prevent the system from shutting down if the
> firmware file isn't available. Or at least it should print a
> warning/error. Mind messing with the code a little to see if skipping
> it kind of works? I probably can also come up with a patch by next
> week.
>
Well, I'd love to but a quick glance at the code caused me to bump into this obscenity:

int
gm200_flcn_reset_wait_mem_scrubbing(struct nvkm_falcon *falcon)
{
nvkm_falcon_mask(falcon, 0x040, 0x00000000, 0x00000000);

if (nvkm_msec(falcon->owner->device, 10,
if (!(nvkm_falcon_rd32(falcon, 0x10c) & 0x00000006))
break;
) < 0)
return -ETIMEDOUT;

return 0;
}

nvkm_msec is #defined to nvkm_usec which in turn is #defined to nvkm_nsec where the loop that the break is related to
appears.> Chris
>>
>>>> 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
>>>> That page also explains what to do if mails like this annoy you.
>>>>
>>>> #regzbot ignore-activity
>>>>
>>>
>>
>