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[Launchpad Bug Tracker <1512185@xxxxxxxxxxxxxxxxxx>]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: qemu (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1512185

Title:
  qemu-nbd on ARM64 deadlock? Stuck in rt_sigtimedwait([BUS ALRM IO],
  ..) and futex(0x7f749ec230, FUTEX_WAIT, ...)

Status in linux package in Ubuntu:
  Incomplete
Status in linux-meta-lts-vivid package in Ubuntu:
  Confirmed
Status in qemu package in Ubuntu:
  Confirmed

Bug description:
  Hi,

  We're seeing this often on our HP Moonshot ARM64 nova-compute nodes
  where qemu-nbd processes would lock up. At the same time, there's also
  a bunch of kernel spew as follows:

  | [605282.018238] block nbd3: Attempted send on closed socket
  | [605282.018242] block nbd3: Attempted send on closed socket
  | [605282.018245] block nbd3: Attempted send on closed socket
  | [605282.018249] block nbd3: Attempted send on closed socket

  swirlix01:

  | hloeung@swirlix01:~$ uname -a
  | Linux swirlix01 3.19.0-30-generic #34~14.04.1-Ubuntu SMP Fri Oct 2 22:15:46 UTC 2015 aarch64 aarch64 aarch64 GNU/Linux
  | hloeung@swirlix01:~$ ps afx | grep qe\\mu-nbd
  | 27782 ?        Ssl    0:00 /usr/bin/qemu-nbd -c /dev/nbd10 /var/lib/nova/instances/ba50751e-56d7-4bc4-8742-1193fe7a138e/disk
  | hloeung@swirlix01:~$ sudo cat /proc/$(ps afx | grep qe\\mu-nbd | awk '{ print $1 }')/stack
  | [<ffffffc0000875b0>] __switch_to+0x74/0x8c
  | [<ffffffc000125dac>] futex_wait_queue_me+0xf4/0x184
  | [<ffffffc0001268b4>] futex_wait+0x154/0x24c
  | [<ffffffc000128638>] do_futex+0x1a0/0x9ec
  | [<ffffffc000128f1c>] SyS_futex+0x98/0x1cc
  | [<ffffffc00008642c>] el0_svc_naked+0x20/0x28
  | [<ffffffffffffffff>] 0xffffffffffffffff

  swirlix08:

  | hloeung@swirlix08:~$ uname -a
  | Linux swirlix08 3.19.0-31-generic #36~14.04.1-Ubuntu SMP Thu Oct 8 10:50:10 UTC 2015 aarch64 aarch64 aarch64 GNU/Linux
  | hloeung@swirlix08:~$ ps afx | grep qe\\mu-nbd
  | 31976 ?        Ssl    0:00 /usr/bin/qemu-nbd -c /dev/nbd6 /var/lib/nova/instances/92ceb061-2ea4-4212-be20-ab0ded6eb3cd/disk
  | hloeung@swirlix08:~$ sudo cat /proc/$(ps afx | grep qe\\mu-nbd | awk '{ print $1 }')/stack
  | [<ffffffc0000875b0>] __switch_to+0x74/0x8c
  | [<ffffffc000125d6c>] futex_wait_queue_me+0xf4/0x184
  | [<ffffffc000126874>] futex_wait+0x154/0x24c
  | [<ffffffc0001285f8>] do_futex+0x1a0/0x9ec
  | [<ffffffc000128edc>] SyS_futex+0x98/0x1cc
  | [<ffffffc00008642c>] el0_svc_naked+0x20/0x28
  | [<ffffffffffffffff>] 0xffffffffffffffff

  swirlix11:

  | hloeung@swirlix11:~$ uname -a
  | Linux swirlix11 3.19.0-31-generic #36~14.04.1-Ubuntu SMP Thu Oct 8 10:50:10 UTC 2015 aarch64 aarch64 aarch64 GNU/Linux
  | hloeung@swirlix11:~$ ps afx | grep qe\\mu-nbd
  | 18149 ?        Ssl    0:00 /usr/bin/qemu-nbd -c /dev/nbd3 /var/lib/nova/instances/84cac137-c1e4-46ac-894a-efcd55ef7e05/disk
  | hloeung@swirlix11:~$ sudo cat /proc/$(ps afx | grep qe\\mu-nbd | awk '{ print $1 }'/stack
  | hloeung@swirlix11:~$ sudo cat /proc/$(ps afx | grep qe\\mu-nbd | awk '{ print $1 }')/stack
  | [<ffffffc0000875b0>] __switch_to+0x74/0x8c
  | [<ffffffc000125d6c>] futex_wait_queue_me+0xf4/0x184
  | [<ffffffc000126874>] futex_wait+0x154/0x24c
  | [<ffffffc0001285f8>] do_futex+0x1a0/0x9ec
  | [<ffffffc000128edc>] SyS_futex+0x98/0x1cc
  | [<ffffffc00008642c>] el0_svc_naked+0x20/0x28
  | [<ffffffffffffffff>] 0xffffffffffffffff

  | hloeung@swirlix11:~$ sudo strace -f -p 18149
  | Process 18149 attached with 3 threads
  | [pid 18150] rt_sigtimedwait([BUS ALRM IO], NULL, NULL, 8 <unfinished ...>
  | [pid 18149] futex(0x7f749ec230, FUTEX_WAIT, 18152, NULL
  | ... (hangs here) ...

  We're using the QEMU package backported from Vivid as per LP:1457639

  | hloeung@swirlix11:~$ apt-cache policy qemu-utils
  | qemu-utils:
  |   Installed: 1:2.2+dfsg-5expubuntu9.5+bug1457639~ubuntu14.04.1
  |   Candidate: 1:2.2+dfsg-5expubuntu9.5+bug1457639~ubuntu14.04.1
  |   Version table:
  |  *** 1:2.2+dfsg-5expubuntu9.5+bug1457639~ubuntu14.04.1 0
  |         500 http://ppa.launchpad.net/canonical-is-sa/arm64-infra-workarounds/ubuntu/ trusty/main arm64 Packages

  I'm also not sure if this is related to LP:1505564, which is for amd64/x86_64.
  --- 
  AlsaDevices:
   total 0
   crw-rw---- 1 root audio 116,  1 Oct 25 17:42 seq
   crw-rw---- 1 root audio 116, 33 Oct 25 17:42 timer
  AplayDevices: Error: [Errno 2] No such file or directory
  ApportVersion: 2.14.1-0ubuntu3.18
  Architecture: arm64
  ArecordDevices: Error: [Errno 2] No such file or directory
  AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
  CRDA: Error: [Errno 2] No such file or directory
  DistroRelease: Ubuntu 14.04
  Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99
  Package: qemu (not installed)
  PciMultimedia:
   
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_GB
   SHELL=/bin/bash
  ProcFB:
   
  ProcKernelCmdLine: console=ttyS0,9600n8r ro
  ProcVersionSignature: Ubuntu 3.19.0-31.36~14.04.1-generic 3.19.8-ckt7
  RfKill: Error: [Errno 2] No such file or directory
  Tags:  trusty uec-images trusty uec-images
  Uname: Linux 3.19.0-31-generic aarch64
  UnreportableReason: This is not an official Ubuntu package. Please remove any third party package and try again.
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm
  _MarkForUpload: True

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