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

[Ben Skeggs]

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
> > >>>>>>>
> > >>>>>>
> > >>>>>
> > >>>>
> >
>