Arch Linux

Can you try with the boot option systemd.legacy_systemd_cgroup_controller or systemctl mask mkinitcpio-generate-shutdown-ramfs.service
If those methods both prevent the error from being shown then I would suspect the issue is 4.13's version of
https://bbs.archlinux.org/viewtopic.php?id=227974 and a duplicate of  FS#54746  see also https://bbs.archlinux.org/viewtopic.php?id=230435

I did have tried out "systemctl mask mkinitcpio-generate-shutdown-ramfs.service". The error message doesn't pop up anymore but still, my laptop can't properly shutdown (frozen in the step).
I have a "Lenovo ThinkPad P50". Shall I execute a command to get more log information?

Would suggest you start a thread on the forums and provide the journal entries from an attempted shutdown.

I'm experiencing this warning (error?) as well, but in my case shutdown isn't freezing. Dell Latitude E5470

@neonkowy see the links in my first comment

How can I get logs of the last shutdown?

https://wiki.archlinux.org/index.php/Systemd#Journal

I have the same issue, and i cannot find any solution! Please report if you have something about this problem!

@breskov which issue the display of the message cgroup: group2: unknown option or the system not shutting down or rebooting?
The former I already covered in my first comment and there is no information on the latter issue.
The latter may well have been fixed already with linux 4.13.5-1 but without more information is required.

Start

Command:

journalctl -b -p err

Result:
Oct 07 10:12:28 linux kernel: DMAR: DRHD: handling fault status reg 3
Oct 07 10:12:28 linux kernel: DMAR: [DMA Read] Request device [00:12.4] fault addr 57fff000 [fault reason 02] Present bit in context entry is clear
Oct 07 10:12:28 linux gnome-session-binary[452]: Unrecoverable failure in required component org.gnome.Shell.desktop
Oct 07 10:12:32 linux kernel: tpm tpm0: Operation Timed out
Oct 07 10:12:32 linux kernel: tpm tpm0: TPM self test failed
Oct 07 10:12:44 linux kernel: mei_wdt mei::05b79a6f-4628-4d7f-899d-a91514cb32ab:02: Could not reg notif event ret=-22

Command:

journalctl -b -1 -p err


Result:

Oct 06 18:04:37 linux kernel: DMAR: DRHD: handling fault status reg 3
Oct 06 18:04:37 linux kernel: DMAR: [DMA Read] Request device [00:12.4] fault addr 57fff000 [fault reason 02] Present bit in context entry is clear
Oct 06 18:04:37 linux gnome-session-binary[445]: Unrecoverable failure in required component org.gnome.Shell.desktop
Oct 06 18:04:41 linux kernel: tpm tpm0: Operation Timed out
Oct 06 18:04:41 linux kernel: tpm tpm0: TPM self test failed
Oct 06 18:04:50 linux ntpd[366]: bind(28) AF_INET6 2003:ca:53cd:dc00:3f86:f747:afa3:e816#123 flags 0x11 failed: Cannot assign requested address
Oct 06 18:04:50 linux ntpd[366]: unable to create socket on wlp4s0 (9) for 2003:ca:53cd:dc00:3f86:f747:afa3:e816#123
Oct 06 18:04:53 linux kernel: mei_wdt mei::05b79a6f-4628-4d7f-899d-a91514cb32ab:02: Could not reg notif event ret=-22
Oct 07 04:12:21 linux ntpd[366]: bind(29) AF_INET6 fd00::2e5e:d26:2231:5149#123 flags 0x11 failed: Cannot assign requested address
Oct 07 04:12:21 linux ntpd[366]: unable to create socket on wlp4s0 (11) for fd00::2e5e:d26:2231:5149#123
Oct 07 10:10:09 linux gdm[365]: GLib: g_variant_new_string: assertion 'string != NULL' failed
Oct 07 10:10:09 linux gdm[365]: GLib: g_variant_new_string: assertion 'string != NULL' failed
Oct 07 10:10:09 linux gdm[365]: GLib: g_hash_table_find: assertion 'version == hash_table->version' failed
Oct 07 10:11:39 linux kernel: wlp4s0: failed to remove key (1, ff:ff:ff:ff:ff:ff) from hardware (-22)
Oct 07 10:11:39 linux kernel: wlp4s0: failed to remove key (2, ff:ff:ff:ff:ff:ff) from hardware (-22)

https://bbs.archlinux.org/viewtopic.php?id=230362

Thanks for your help, I have learned a lot!

I had the cgroup: group2: unknown option "" message, and I was unable to shutdown or reboot my system.

I also had these messages:

DMAR: DRHD: handling fault status reg 3
wlp4s0: failed to remove key (1, ff:ff:ff:ff:ff:ff) from hardware (-22)

But fortunately intel_iommu=off worked well for me too.

Thank you very much loqus!

same problem for me,
masking mkinitcpio-generate-shutdown-ramfs.service helped for the cgroup2 error, but my notebook didn't turn of though.
What solved the power-off-problem was an update to 4.13.5-1-ARCH (it's in testing)