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

[Steve Langasek]

On Fri, Jun 07, 2013 at 04:59:51AM -0000, Martin Pitt wrote:
> Does that mean we should revert the firmware lookup from /system and
> /vendor in udev?

Possibly.  You were rather quick on the draw in uploading that change, I was
expecting more discussion first. ;-)

For the moment, lxc-android-config is diverting
/lib/udev/rules.d/50-firmware.rules, which stops *all* firmware loading from
udev.  This is certainly not the preferred behavior; if possible, I think we
should prefer udev to handle all the firmware loading and take ueventd out
of the picture entirely, so that we can have a single, consistent,
upstreamed handler for all of this.  However, Oliver seems to have some
concerns about the robustness / maintainability of this, so I haven't pushed
things in this direction so far.

If we could trust udev to handle all the events once for both sides, then
the ueventd ordering problem would go away, the need for diversions would go
away, and we would want to stick with udev reading from /system/firmware and
/vendor/firmware directly.  But it's not certain yet that we want to do
that, so I think some more investigation is still needed before we decide.

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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:
  Fix Released
Status in “systemd” package in Ubuntu:
  Incomplete

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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