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

[Karol Herbst]

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.

> 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
> >>
> >
>