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

[Chris Clayton]

Hi.

Is it likely that this fix will be sumbmitted to mainline during the ongoing 6.3 development cycle?

Chris

On 20/02/2023 22:16, Ben Skeggs wrote:
> On Mon, 20 Feb 2023 at 21:27, Karol Herbst <kherbst@xxxxxxxxxx> wrote:
>>
>> On Mon, Feb 20, 2023 at 11:51 AM Chris Clayton <chris2553@xxxxxxxxxxxxxx> wrote:
>>>
>>>
>>>
>>> On 20/02/2023 05:35, Ben Skeggs wrote:
>>>> On Sun, 19 Feb 2023 at 04:55, Chris Clayton <chris2553@xxxxxxxxxxxxxx> wrote:
>>>>>
>>>>>
>>>>>
>>>>> On 18/02/2023 15:19, Chris Clayton wrote:
>>>>>>
>>>>>>
>>>>>> 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
>>>>>
>>>>> I think someone who knows the code needs to look at this. What I can confirm is that after a freeze, I waited for 90
>>>>> seconds for a timeout to occur, but it didn't.
>>>> Hey,
>>>>
>>>> Are you able to try the attached patch for me please?
>>>>
>>>> Thanks,
>>>> Ben.
>>>>
>>>
>>> Thanks Ben.
>>>
>>> Yes, this patch fixes the lockup on reboot and poweroff that I've been seeing on my laptop. As you would expect,
>>> offloaded rendering is still working and the discrete GPU is being powered on and off as required.
>>>
>>> Thanks.
>>>
>>> Reported-by: Chris Clayton <chris2553@xxxxxxxxxxxxxx>
>>> Tested-by: Chris Clayton <chris2553@xxxxxxxxxxxxxx>
>>>
>>
>> Ben, did you manage to get push rights to drm-misc by now or should I
>> just pick the patch and push it through -fixes?
> Feel free to pick it up!
> 
> Thank you,
> Ben.
> 
>>
>>>>>
>>>>>
>>>>> .> 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
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>
>>