Random hangs after upgrade to 4.4.0-45, possibly cgroup related

Apologize in advance is anything is missing from this bug report.

After upgrading to 4.4.0-45 we have started to experience random kernel lockups. I have attached a sample from the syslog which I managed to catch after one of these events. In other cases, nothing was written to the syslog.

I notice that the cgroup system features here and there in the log, and the hanging server uses cgroups and namespaces heavily, so I suspect it is related. Sadly I don't know enough of the kernel to decipher the error I got further than that.

Another unusual thing we do on this server, which may possibly be related, is that we regularly clear the caches ("echo 3 > /proc/sys/vm/drop_caches")

/Pehr

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-45-generic 4.4.0-45.66
ProcVersionSignature: Ubuntu 4.4.0-45.66-generic 4.4.21
Uname: Linux 4.4.0-45-generic x86_64
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Oct 22 22:52 seq
 crw-rw---- 1 root audio 116, 33 Oct 22 22:52 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Date: Sat Oct 22 23:37:59 2016
HibernationDevice: RESUME=/dev/mapper/template--16--vg-swap_1
InstallationDate: Installed on 2016-04-22 (183 days ago)
InstallationMedia: Ubuntu-Server 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.3)
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Lsusb: Error: command ['lsusb'] failed with exit code 1:
MachineType: VMware, Inc. VMware Virtual Platform
PciMultimedia:

ProcFB: 0 svgadrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-45-generic root=/dev/mapper/template--16--vg-root ro cgroup_enable=memory swapaccount=1
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-45-generic N/A
 linux-backports-modules-4.4.0-45-generic N/A
 linux-firmware 1.157.4
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/17/2015
dmi.bios.vendor: Phoenix Technologies LTD
dmi.bios.version: 6.00
dmi.board.name: 440BX Desktop Reference Platform
dmi.board.vendor: Intel Corporation
dmi.board.version: None
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 1
dmi.chassis.vendor: No Enclosure
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnPhoenixTechnologiesLTD:bvr6.00:bd09/17/2015:svnVMware,Inc.:pnVMwareVirtualPlatform:pvrNone:rvnIntelCorporation:rn440BXDesktopReferencePlatform:rvrNone:cvnNoEnclosure:ct1:cvrN/A:
dmi.product.name: VMware Virtual Platform
dmi.product.version: None
dmi.sys.vendor: VMware, Inc.