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[Rudolf Leitgeb <1584533@xxxxxxxxxxxxxxxxxx>]

Thanks for your reply, before I followed your recommended steps I did a
system upgrade as recommended by ubuntu update manager. Since this also
updated systemd which is AFAIK pretty basic to the system, I tested both
after the upgrade AND after the switch to this mainline kernel you
recommended. Behavior became much stranger with the regular system
update, and in both cases (i.e. ubuntu kernel and mainline kernel) the
system behaved more or less the same, as far as wlan is concerned:

- After a reboot everything looks normal, wlan comes on even before
login, and stays intact after login. network manager applet in top bar
shows wlan networks plus the one I am connected to.

- After a sleep/wakeup, network manager shows loss of wlan connection.
No existing wlan networks are shown in wireless network list. Opening
"connect to hidden network" menu lists all networks I ever connected to,
but will not allow me to hit connect with any of them in the list,
connect button is grayed out.

- Now here comes the freaky part: in SOME of these instances I am
actually connected to my home wlan! This is not shown directly in
network manager, only after opening connection information window one
can see that there is a virbr0 device, and an active wlan0 device.

After many reboots and sleep/wakeup cycles with both kernels (ubuntu and
mainline), I can state that there is about a 50% likelyhood that wlan
becomes active, and that if wlan is active after one sleep/wakeup cycle,
chances are high that it will work in consecutive sleep/wakeup cycles.
In two cases (one for each kernel) I could create a special case: wlan
active after reboot, active again after sleep/wakeup, then inactive
after next sleep/wakeup. Since these cases yield a very compact dmesg
file, I post both of them here.

I hope this helps pinning down the issue, please let me know if you need
further data or tests.

Cheers,

Rudi

** Attachment added: "dmesg file created with regular ubuntu kernel: reboot, sleep/wakeup + working wlan, sleep/wakeup + broken wlan"
   https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1584533/+attachment/4669692/+files/dmesg-flaky-ubuntu

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https://bugs.launchpad.net/bugs/1584533

Title:
  Lenovo X220 unable to wlan after resume from sleep

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  I just upgraded to Ubuntu 16.04, and now whenever I wake up my laptop
  from sleep (hibernate doesn't work due to encrypted home directory), I
  am unable to connect to any wlan network. After a hot reboot or cold
  start everything is back to normal.

  Network manager would allow me to select already known wlan networks
  through "connect to hidden network", however, it would not allow me to
  establish the actual connection (connect button never becomes active).

  I will attach four files to this bug report:

  1. dmesg-pastreboot: dmesg after a hot reboot
  2. dmesg-pastsleep: dmesg after wakeup from sleep
  3. syslog-pastreboot: syslog snippet from timeframe after reboot
  4. syslog-pastsleep: syslog snippet from timeframe after wakeup from sleep

  Please let me know, if you need any further data or info.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: linux-image-4.4.0-22-generic 4.4.0-22.40
  ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
  Uname: Linux 4.4.0-22-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  rudolf     2944 F.... pulseaudio
  CurrentDesktop: Unity
  Date: Sun May 22 22:31:10 2016
  EcryptfsInUse: Yes
  InstallationDate: Installed on 2011-05-24 (1825 days ago)
  InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
  MachineType: LENOVO 429135G
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-22-generic root=UUID=080f751d-bbec-44b2-bd86-f4db52f4dddf ro quiet splash i915.semaphores=1 vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-4.4.0-22-generic N/A
   linux-backports-modules-4.4.0-22-generic  N/A
   linux-firmware                            1.157
  SourcePackage: linux
  UpgradeStatus: Upgraded to xenial on 2016-05-18 (4 days ago)
  dmi.bios.date: 04/01/2011
  dmi.bios.vendor: LENOVO
  dmi.bios.version: 8DET42WW (1.12 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 429135G
  dmi.board.vendor: LENOVO
  dmi.board.version: Not Available
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Not Available
  dmi.modalias: dmi:bvnLENOVO:bvr8DET42WW(1.12):bd04/01/2011:svnLENOVO:pn429135G:pvrThinkPadX220:rvnLENOVO:rn429135G:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
  dmi.product.name: 429135G
  dmi.product.version: ThinkPad X220
  dmi.sys.vendor: LENOVO

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