Bug#805605: xserver-xorg-core: crash/freeze on logout of tty that was previously serving as a vt for X

[Justus Piater <Justus-dev@Piater.name>]

I believe I am seeing the same bug (similar symptoms, similar X
backtrace).  It is triggered simply by logging out on some other VT;
multiple X servers are not required.  To reproduce on a freshly-booted
machine:

- log in (on VT1)
- startx
- switch to VT2
- log in
- log out

At this point, instead of leaving me on VT2 with a login prompt, it
automatically switches back to VT1, which is stuck as Brian describes.

Brian, can you reproduce this? If so, I suggest changing the bug title
to something like:

  xserver-xorg-core: crash/freeze on logout on another vt

There appears to be some non-determinism:

- Sometimes the VT1 terminal still shows the mouse pointer (on the
  otherwise empty i3 desktop); sometimes not.  (On attempting to switch
  to a different VT, the mouse pointer, if still present, always
  disappears.)

- During my many trials, in a single case, logging out on VT2 worked as
  expected, except that screen brightness was very low.

I'm using an up-to-date Stretch, with rootless X and no display manager,
using the i915 GPU driver (like Brian apparently, but with a different
Intel graphics controller, "00:02.0 VGA compatible controller [0300]:
Intel Corporation Core Processor Integrated Graphics Controller
[8086:0046] (rev 02)").