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[Martin Pitt <martin.pitt@xxxxxxxxxx>]

Darn, I now get the "instance kills itself after some time" on the 4x
CPU as well. nova console-log shows the blurb below and ssh and lxd
ports are dead (so I can't learn anything further from the box than
console-log).

Ubuntu Xenial Xerus (development branch) lxd-armhf2 ttyAMA0

lxd-armhf2 login: [  954.144506] INFO: rcu_sched detected stalls on CPUs/tasks:
[  954.145743]  1-...: (79 GPs behind) idle=284/0/0 softirq=407182/407182 fqs=1 
[  954.147202]  (detected by 3, t=15002 jiffies, g=21817, c=21816, q=1563)
[  954.148590] Call trace:
[  954.149123] rcu_sched kthread starved for 15002 jiffies! g21817 c21816 f0x0 s3 ->state=0x1
[ 3000.217089] INFO: task systemd:1 blocked for more than 120 seconds.
[ 3000.218529]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3000.219628] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3000.221310] Call trace:
[ 3000.222562] INFO: task kworker/0:2:12463 blocked for more than 120 seconds.
[ 3000.223985]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3000.225146] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3000.226741] Call trace:
[ 3000.227306] INFO: task (d-logind):15441 blocked for more than 120 seconds.
[ 3000.228685]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3000.229834] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3000.231469] Call trace:
[ 3120.231067] INFO: task systemd:1 blocked for more than 120 seconds.
[ 3120.232501]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3120.233629] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3120.235393] Call trace:
[ 3120.236702] INFO: task kworker/0:2:12463 blocked for more than 120 seconds.
[ 3120.238188]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3120.239398] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3120.241140] Call trace:
[ 3120.241716] INFO: task (d-logind):15441 blocked for more than 120 seconds.
[ 3120.243223]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3120.244366] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3120.245945] Call trace:
[ 3240.244955] INFO: task systemd:1 blocked for more than 120 seconds.
[ 3240.246398]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3240.247526] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3240.249272] Call trace:
[ 3240.250568] INFO: task kworker/0:2:12463 blocked for more than 120 seconds.
[ 3240.252060]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3240.253280] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3240.254966] Call trace:
[ 3240.255549] INFO: task (d-logind):15441 blocked for more than 120 seconds.
[ 3240.257073]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3240.258259] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3240.259906] Call trace:
[ 3360.258901] INFO: task systemd:1 blocked for more than 120 seconds.
[ 3360.260349]       Not tainted 4.4.0-2-generic #16-Ubuntu
[ 3360.261475] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3360.263224] Call trace:

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https://bugs.launchpad.net/bugs/1531768

Title:
  [arm64] multithreaded processes get locked up in futexes

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  I created an 8 CPU arm64 instance on Canonical's Scalingstack (which I
  want to use for armhf autopkgtesting in LXD). I started with wily as
  that has lxd available (it's not yet available in trusty nor the PPA
  for arm64).

  However, pretty much any LXD task that I do (I haven't tried much
  else) on this machine takes unbearably long. A simple "lxc profile set
  default raw.lxc lxc.seccomp=" or "lxc list" takes several minutes.

  I see tons of

  [ 1020.971955] rcu_sched kthread starved for 6000 jiffies! g1095 c1094 f0x0
  [ 1121.166926] INFO: task fsnotify_mark:69 blocked for more than 120 seconds.

  in dmesg (the attached apport info has the complete dmesg).

  ProblemType: Bug
  DistroRelease: Ubuntu 15.10
  Package: linux-image-4.2.0-22-generic 4.2.0-22.27
  ProcVersionSignature: User Name 4.2.0-22.27-generic 4.2.6
  Uname: Linux 4.2.0-22-generic aarch64
  AlsaDevices:
   total 0
   crw-rw---- 1 root audio 116,  1 Jan  7 09:18 seq
   crw-rw---- 1 root audio 116, 33 Jan  7 09:18 timer
  AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
  ApportVersion: 2.19.1-0ubuntu5
  Architecture: arm64
  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:
  CRDA: N/A
  Date: Thu Jan  7 09:24:01 2016
  IwConfig:
   eth0      no wireless extensions.

   lo        no wireless extensions.

   lxcbr0    no wireless extensions.
  Lspci:
   00:00.0 Host bridge [0600]: Red Hat, Inc. Device [1b36:0008]
    Subsystem: Red Hat, Inc Device [1af4:1100]
    Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
    Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
  Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99
  PciMultimedia:

  ProcEnviron:
   TERM=screen
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB:

  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-22-generic root=LABEL=cloudimg-rootfs earlyprintk
  RelatedPackageVersions:
   linux-restricted-modules-4.2.0-22-generic N/A
   linux-backports-modules-4.2.0-22-generic  N/A
   linux-firmware                            1.149.3
  RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
  SourcePackage: linux
  UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
  UpgradeStatus: No upgrade log present (probably fresh install)

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