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[Brian Murray <brian@xxxxxxxxxx>]

** Package changed: ubuntu => linux (Ubuntu)

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https://bugs.launchpad.net/bugs/1516216

Title:
  X fails to start, starting with kernel version 3.13.0-66 including
  3.13.0-68

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  System: Ubuntu 14.04
  Graphics Card: Geforce GTX 670
  Graphics Driver: nvidia-352.55

  Starting with kernel 3.13.0-66, the start of X / default display manager results in a black screen. My observations are:
  - When I get this black screen, I cannot CTRL+ALT+F1 into a text console
  - Pressing the power button in this state leads to a proper shutdown (which I guess means that it is not a complete kernel panic).
  - When using these latest kernel, the graphics behavior during boot-up also has changed. Instead of a graphical animation, the system boots in text mode (I can see the syslog output), and at the moment I should get the display manager, the screen goes black.

  My work-around so far has been to boot kernel 3.13.0-65 instead of
  3.13.0-66, 3.13.0-67, or 3.13.0-68. So far this has worked reliably.
  However today, booting kernel 3.13.0-65 has resulted in a black screen
  as well. Fortunately, I found a new work-around: I can boot kernel
  3.13.0-68 in recovery mode, and chose simply "continue" in the
  recovery console. With this modification of the boot process, X will
  start.

  In the syslog, I can see some suspicious messages, around the time X
  should start: "BUG: unable to handle kernel NULL pointer dereference
  at (null)". I have attached a syslog contain some failed starts as
  well as a successful one.

  Another suspicion is that the problem is related having an Oculus Rift
  DK2 connected. In particular, this requires to use a custom Xorg.conf
  which runs individual X screens for the main display and the Oculus
  Rift.

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