Wacom + GTK + old configuration causes Xorg to segfault with error 4 under Kubuntu Jaunty

[Chris Drost]

Binary package hint: xorg

In the latest aptitude full-upgrade I did (running Kubuntu Jaunty) there were a couple of packages that said they were "recommended but would not be installed." -- I more or less shrugged these off, but I forgot to write them down.

After the computer rebooted, a whole mess of things happened: the biggest one is that now, whenever I start any GTK-based app, (tested with GIMP, Firefox, and CellWriter) X segfaults.

Since the bug is trivially reproducable, I've recorded the /var/log/syslog messages on four separate occasions after deliberately triggering this bug. They all have these lines in common:

Xorg[*****]: segfault at d0 ip 0000000000496786 sp 00007fff*******0 error 4 in Xorg[400000+1c3000]
[drm:gm45_get_vblank_counter] *ERROR* trying to get vblank count for disabled pipe 0
kdm[****]: X server for display :0 terminated unexpectedly

I have also seen these three lines erratically appear; they suggestively implicate Qt 4.5, but it may be that Qt is just noticing the X segfault:

python[17124]: segfault at 30 ip 00007fc440976bb5 sp 00007fff4a0e38f8 error 4 in libQtCore.so.4.5.0[7fc440807000+240000]
ksmserver[17070]: segfault at 8 ip 00007f2045afbe2b sp 00007f203b28f648 error 4 in libQtDBus.so.4.5.0[7f2045ab7000+74000]
ksmserver[19042]: segfault at 8 ip 00007f4c24ecde2b sp 00007f4c1a661648 error 4 in libQtDBus.so.4.5.0[7f4c24e89000+74000]

There is also a backtrace recorded in /var/logs/Xorg.0.log.old file, which looks like this:

0: /usr/bin/X(xorg_backtrace+0x26) [0x4f1b66]
1: /usr/bin/X(xf86SigHandler+0x41) [0x485a61]
2: /lib/libc.so.6 [0x7f2d63995040]
3: /usr/lib/xorg/modules/input//wacom_drv.so [0x7f2d61795035]
4: /usr/bin/X(ActivateDevice+0x3e) [0x447a8e]
5: /usr/bin/X(OpenInputDevice+0x10) [0x4968e0]
6: /usr/bin/X(ProcXOpenDevice+0xa3) [0x545823]
7: /usr/bin/X(Dispatch+0x364) [0x44e304]
8: /usr/bin/X(main+0x3bd) [0x433d8d]
9: /lib/libc.so.6(__libc_start_main+0xe6) [0x7f2d639805a6]
10: /usr/bin/X [0x433219]
Saw signal 11. Server aborting.

An upcoming comment will discuss this more in-depth.

ProblemType: Bug
Architecture: amd64
DistroRelease: Ubuntu 9.04
Package: xorg 1:7.4~5ubuntu18
ProcEnviron:
 LANGUAGE=
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersion: Linux version 2.6.28-11-generic (buildd@crested) (gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4) ) #41-Ubuntu SMP Wed Apr 8 04:39:23 UTC 2009
SourcePackage: xorg
Uname: Linux 2.6.28-11-generic x86_64

[Chris Drost (chris-drostie)]

I don't see a way to refile this post under a different project, but it probably belongs under xserver-xorg and possibly under xserver-xorg-input-wacom.

I've resolved my personal issue to my own satisfaction, although I'm not sure that xorg should segfault on this particular issue. The key to the puzzle came with a more extensive problem description in apport, which I tried to submit but didn't succeed. In any case, part of the apport response discussed that it was trying to remove the Wacom device. That convinced me that Qt, which I was previously staring very hard at, was not the problem and that I should check on the Wacom settings in my xorg.conf file.

When those were removed, two things happened: (1) GTK programs did indeed start again; (2) my tablet input device still worked, as if by magic. (It didn't before I put those lines there!)

So, to place the bug more narrowly: there were some recent patches in xserver-xorg-input-wacom. I believe that one of these patches automatically configures the tablet device for you -- a process that previously had to be done manually in xorg.conf. If the xorg.conf file specifies a manual configuration, apparently everything goes smooth for most applications, but GTK for some reason tries to remove the device and/or create a new one -- the details aren't clear to me. When the device gets removed and then recreated, Xorg apparently gets confused and segfaults.

I have the feeling that not all of that is right, but in any case: something weird is happening that probably shouldn't be happening, even though the userbase it affects is probably a fringe case.

[Bryce Harrington (bryce)]

Nice sleuthing! Yes, sounds like it's a bug by the wacom-tools update, which occurred just recently.

Sounds like the update procedure ought to force commenting out any existing wacom entries in xorg.conf. Assigning to timo to look into.

[Julius Bloch (jbloch)]

Hi,
I don't know if it is the same bug. But I have a ibm thinkpad x41 tablet where I got the same error.
But I can't start X.
dmesg shows this if I try to start X:
[ 102.124027] Xorg[3880]: segfault at 10 ip 080d8832 sp bff47a70 error 4 in Xorg[8048000+19d000]
[ 102.300148] [drm:i915_get_vblank_counter] *ERROR* trying to get vblank count for disabled pipe 0
[ 106.825618] [drm:i915_setparam] *ERROR* unknown parameter 4
[ 106.825644] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 107.742091] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 111.760533] Xorg[3912]: segfault at 10 ip 080d8832 sp bfdd6900 error 4 in Xorg[8048000+19d000]
[ 111.936152] [drm:i915_get_vblank_counter] *ERROR* trying to get vblank count for disabled pipe 0
[ 346.907953] [drm:i915_setparam] *ERROR* unknown parameter 4
[ 346.908488] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 347.910566] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 352.548593] Xorg[4042]: segfault at 10 ip 080d8832 sp bfc2cf50 error 4 in Xorg[8048000+19d000]
[ 352.724143] [drm:i915_get_vblank_counter] *ERROR* trying to get vblank count for disabled pipe 0
[ 355.619586] [drm:i915_setparam] *ERROR* unknown parameter 4
[ 355.619637] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 356.652732] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 361.231635] Xorg[4074]: segfault at 10 ip 080d8832 sp bff31260 error 4 in Xorg[8048000+19d000]
[ 361.564107] [drm:i915_get_vblank_counter] *ERROR* trying to get vblank count for disabled pipe 0
[ 364.316599] [drm:i915_setparam] *ERROR* unknown parameter 4
[ 364.316650] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 365.319237] [drm:i915_getparam] *ERROR* Unknown parameter 6
[ 370.624554] [drm:i915_get_vblank_counter] *ERROR* trying to get vblank count for disabled pipe 0

[Jasper Mattsson (jasper-mattsson)]

I'm seeing this issue with Wine programs requiring tablet. i386, X41Tablet too.

Also, Intel video driver crashes X, sometimes GDM comes back and reboot is not required, sometimes I can't even get to the virtual console.

I'm using Xorg.conf for Wacom, since the autodetected wacom doesn't support rotating the tablet.

Xorg log most relevant parts:

BEGIN xf86WcmProc dev=0x92c1788 priv=0x92eef50 type=eraser((null)) flags=97 fd=153813100 what=INIT
xf86WcmDevOpen

Backtrace:
0: /usr/bin/X(xorg_backtrace+0x3b) [0x813518b]
1: /usr/bin/X(xf86SigHandler+0x55) [0x80c7be5]
2: [0xb7f04400]
3: /usr/lib/xorg/modules/input//wacom_drv.so [0xb77719c2]
4: /usr/bin/X(ActivateDevice+0x4f) [0x808662f]
5: /usr/bin/X(OpenInputDevice+0x24) [0x80d89a4]
6: /usr/bin/X(ProcXOpenDevice+0xaa) [0x818bf8a]
7: /usr/bin/X [0x8187713]
8: /usr/bin/X(Dispatch+0x33f) [0x808d57f]
9: /usr/bin/X(main+0x3bd) [0x80722ed]
10: /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe5) [0xb7ad8775]
11: /usr/bin/X [0x80717a1]
Saw signal 11. Server aborting.
(II) UnloadModule: "wacom"
(II) UnloadModule: "wacom"
(II) UnloadModule: "wacom"

Xorg.conf relevant parts:

Section "InputDevice"
 Driver "wacom"
 Identifier "stylus"
 Option "Device" "/dev/input/wacom"
 Option "Type" "stylus"
 Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "ServerLayout"
...
#Uncomment if you have a wacom tablet
 InputDevice "stylus" "SendCoreEvents"
 InputDevice "cursor" "SendCoreEvents"
 InputDevice "eraser" "SendCoreEvents"
EndSection

[Chris Drost (chris-drostie)]

Jasper: did you already try the fix from bug # 358643 ? It's important if we find out that this fix isn't universal, and you didn't say anything about it.

Just to recap that fix here, Timo Aaltonen has a personal package archive with patched .deb packages of xserver-xorg-core, which are available at this URL:

http://ppa.launchpad.net/tjaalton/ppa/ubuntu/pool/main/x/xorg-server/

For at least two of us, telling dpkg to install that .deb over our current version of xserver-xorg-core has fixed this bug.

[Jasper Mattsson (jasper-mattsson)]

Chris: I tried it now, it works, thank you for your reply.

Because the bug symptoms in that report weren't similar, I thought it wasn't really a duplicate of this bug. Apparently the solution is the same, so it is a dup after all.