Comment 24 for bug 1817738

I'm seeing this same issue (hung syscall on VT) from systemd-sleep on a suspend operation with Xubuntu (and therefore lightdm). I see a similar stack-trace too. 18.04 with 4.15.0-56-lowlatency.

https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1744370

apt list plymouth
Listing... Done
plymouth/bionic-updates,now 0.9.3-1ubuntu7.18.04.2 amd64 [installed,automatic]

$ sudo cat /proc/$(pidof systemd-sleep)/stack

[<0>] __vt_event_wait.isra.2.part.3+0x40/0x90
[<0>] vt_waitactive+0x7b/0xd0
[<0>] vt_move_to_console+0x46/0xc0
[<0>] pm_prepare_console+0x23/0x40
[<0>] pm_suspend+0x19c/0x3b0
[<0>] state_store+0x85/0xf0
[<0>] kobj_attr_store+0x12/0x20
[<0>] sysfs_kf_write+0x3c/0x50
[<0>] kernfs_fop_write+0x125/0x1a0
[<0>] __vfs_write+0x1b/0x40
[<0>] vfs_write+0xb1/0x1a0
[<0>] SyS_write+0x55/0xc0
[<0>] do_syscall_64+0x73/0x130
[<0>] entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[<0>] 0xffffffffffffffff