Bug#838050: GDM3-only behaviour; Wayland not totally broken; bad tablets break even that

[Andrew Chadwick]

The behaviour in gdm3 alone (outside of a user session) is different 
from tablet to tablet.

* Wacom Intuos5 USB: no crashes, pen functions as a second crosshair 
pointer
* HUION H610PRO USB: no crashes, pen functions as a second crosshair 
pointer
* Genius EasyPen i405X USB: crashes gnome-session in this environment 
as well, repeatedly, same segfault from gnome-shell. systemd appears to 
be desperately trying to launch Xorg instead afterwards? Which then 
*also* segfaults repeatedly.

The Huion and Wacom tablets work inside GNOME-on-Wayland user sessions, 
and gtk3-demo's "Touch and Drawing Tablets" module presents their extra 
axes (pressure, or pressure+tilt+distance, respectively). However using 
Wayland is not really a great workaround currently given how crashy it 
is (xwayland 2:1.18.4-1, pressing Alt kills Chromium, wow.)

The Genius tablet is well known as a horrid crashy mess generally, 
which is why I bought it. This behaviour is new even for that, however.

---------------------8<-----------------
Sep 18 03:17:32 spatula kernel: [50703.338856] usb 2-1: new low-speed 
USB device number 35 using xhci_hcd
Sep 18 03:17:32 spatula kernel: [50703.532827] usb 2-1: New USB device 
found, idVendor=0458, idProduct=5010
Sep 18 03:17:32 spatula kernel: [50703.532834] usb 2-1: New USB device 
strings: Mfr=1, Product=2, SerialNumber=0
Sep 18 03:17:32 spatula kernel: [50703.532838] usb 2-1: Product: 
EasyPen i405X
Sep 18 03:17:32 spatula kernel: [50703.532841] usb 2-1: Manufacturer: 
Genius
Sep 18 03:17:32 spatula kernel: [50703.561689] input: Genius EasyPen 
i405X as 
/devices/pci0000:00/0000:00:14.0/usb2/2-1/2-1:1.0/0003:0458:5010.0040/input/input175
Sep 18 03:17:32 spatula kernel: [50703.615183] kye 0003:0458:5010.0040: 
input,hiddev0,hidraw2: USB HID v1.11 Device [Genius EasyPen i405X] on 
usb-0000:00:14.0-1/input0
Sep 18 03:17:32 spatula mtp-probe: checking bus 2, device 35: 
"/sys/devices/pci0000:00/0000:00:14.0/usb2/2-1"
Sep 18 03:17:32 spatula mtp-probe: bus: 2, device: 35 was not an MTP 
device
Sep 18 03:17:33 spatula gnome-shell[29393]: Could not get tablet 
information for 'Genius EasyPen i405X': (null)
Sep 18 03:17:33 spatula kernel: [50704.317185] gnome-shell[29393]: 
segfault at 10 ip 00007fd62869e844 sp 00007ffe16cebae0 error 4 in 
libwacom.so.2.5.0[7fd62869b000+9000]
Sep 18 03:17:33 spatula org.gnome.Shell.desktop[29393]: (EE)
Sep 18 03:17:33 spatula org.gnome.Shell.desktop[29393]: Fatal server 
error:
Sep 18 03:17:33 spatula org.gnome.Shell.desktop[29393]: (EE) failed to 
dispatch Wayland events: Broken pipe
Sep 18 03:17:33 spatula org.gnome.Shell.desktop[29393]: (EE)
[... one more segfault ...]
Sep 18 03:17:35 spatula gdm3: Child process -29545 was already dead.
Sep 18 03:17:35 spatula gdm3: Child process 29534 was already dead.
Sep 18 03:17:35 spatula gdm3: Unable to kill session worker process
Sep 18 03:17:35 spatula systemd[1]: Started Session c22 of user 
Debian-gdm.
Sep 18 03:17:35 spatula udev-acl.ck[29583]: g_slice_set_config: 
assertion 'sys_page_size == 0' failed
Sep 18 03:17:35 spatula /usr/lib/gdm3/gdm-x-session[29582]: (--) Log 
file renamed from "/var/lib/gdm3/.local/share/xorg/Xorg.pid-29585.log" 
to "/var/lib/gdm3/.local/share/xorg/Xorg.0.log"
Sep 18 03:17:35 spatula /usr/lib/gdm3/gdm-x-session[29582]: X.Org X 
Server 1.18.4
Sep 18 03:17:35 spatula /usr/lib/gdm3/gdm-x-session[29582]: Release 
Date: 2016-07-19
Sep 18 03:17:35 spatula /usr/lib/gdm3/gdm-x-session[29582]: X Protocol 
Version 11, Revision 0
[... starts up, then a stream of new segfaults ...]
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