[Bug 1187189] Re: Kernel crash and reboot when accessing video device

[Steve Langasek]

Fundamentally this is a kernel bug, for panicing when the firmware load
fails.  But we should also be working through the issue of udev+ueventd
double-handling of firmware requests.  The change for bug #1187616
already lets udev read firmware from /system/firmware +
/vendor/firmware, but we may not have the ordering right to make sure
those mount points are available before udev starts.  And Oliver has
argued that there are some reasons to want ueventd to continue to handle
certain drivers, due to options being set in the kernel - so we don't
necessarily want to have udev take over entirely for ueventd.

In the short term, I think we'll want to work around this by having lxc-
android-config divert the udev rules files to disable them.  This will
prevent us from being able to load firmware from /lib/firmware, but we
actually don't do that anyway since everything is already in
/system/firmware on these systems.

** Also affects: lxc-android-config (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1187189

Title:
  Kernel crash and reboot when accessing video device

Status in “linux-mako” package in Ubuntu:
  Confirmed
Status in “lxc-android-config” package in Ubuntu:
  New
Status in “systemd” package in Ubuntu:
  New

Bug description:
  While working on the container flip, we noticed that starting udev and
  calling udevadm trigger would cause the device to reboot instantly.

  After some effort, we tracked this down to video4linux and
  specifically the 60-persistent-v4l rules file. Looking into it, we see
  it's calling v4l_id and that's what's causing the reboot.

  Here's some basic reproducing step for saucy post-container flip:
  root at android:/ # mv /lib/udev/rules.d/60-persistent-v4l.rules /root
  root at android:/ # start udev
  udev start/running, process 1016
  root at android:/ # start udevtrigger                                             
  udevtrigger stop/waiting
  root at android:/ # cat /dev/video38
  --- reboot ---

  It looks like any attempt to open the video device causes the panic
  and reboot.

  Unfortunately I don't have any way to get a console or any kernel
  debug information so all I can tell is that there's something very
  wrong going with that video device.

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