(As this bug probably has something to do with the interaction between the KDE app(s) in question and GNOME and X, I'm not totally sure where to put this.)
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updated tl;dr: If I'm using a KDE app during a GNOME session, sometimes it will log me out, which upon further research is caused by an X Server crash. This happens when a KDE program segfaults. The problem is that I know quite well that the segmentation faults in KDE apps are usually caught by the crash handler. And since I don't have a KDE desktop, I don't think the crash handler actually catches these segfaults when one is not using the full KDE desktop. Obviously, it probably should.
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I'm using the usual Ubuntu (GNOME) install, updated regularly but running one or two KDE-based apps on top of it - the one that most commonly triggers this condition is KolourPaint on top of GNOME, but that's because that's the one I most commonly use. (Then again, I'm using it because GNOME-based paint program clones are not nearly at that level of development.)
This is what I generally do:
1. Log in and start any GNOME programs. This works fine.
2. Start the KDE-based program. This also works fine.
3. At some point while fooling around with said KDE-based program, the entire X Server is brought down. No, I can't seem to isolate this to any particular action or set of actions.
Notes:
1. This error seems to have replaced the fact that when said program crashes, it brings up an error screen with the intent to report a bug, where the button to actually report said bug is nonfunctional (due to the fact that I do not actually have a full complement of Kubuntu packages).
2. The error in question, both in the previous report-a-bug screen and now with X crashes, seems to be some sort of segmentation fault. Not that I know what that means.
3. I didn't report this error when it brought up the KDE error screen. I report it now. That's because I'd vastly prefer catching bugs, even without saving program state, to completely upending X. Ending every program without so much as giving the user a chance to save state is /not nice/.
4. Despite the fact that I'm not totally sure whether this is an X bug or not, I used the report-with-X-info anyway; it might be useful.
5. I'm going to get a backtrace as soon as I can.
Backtrace:
0: /usr/bin/X (xorg_backtrace+0x3b) [0x80e937b]
1: /usr/bin/X (0x8048000+0x61c7d) [0x80a9c7d]
2: (vdso) (__kernel_rt_sigreturn+0x0) [0x986410]
3: /usr/lib/xorg/modules/libfb.so (fbSegment+0x215) [0xe68045]
4: /usr/lib/xorg/modules/libfb.so (fbZeroLine+0x13c) [0xe64bec]
5: /usr/lib/xorg/modules/libfb.so (fbPolyLine+0x72) [0xe648d2]
6: /usr/lib/xorg/modules/drivers/intel_drv.so (0xb69000+0x63695) [0xbcc695]
7: /usr/lib/xorg/modules/drivers/intel_drv.so (0xb69000+0x5c26b) [0xbc526b]
8: /usr/bin/X (0x8048000+0xda0d8) [0x81220d8]
9: /usr/bin/X (0x8048000+0x2860b) [0x807060b]
10: /usr/bin/X (0x8048000+0x2a477) [0x8072477]
11: /usr/bin/X (0x8048000+0x1ed7a) [0x8066d7a]
12: /lib/tls/i686/cmov/libc.so.6 (__libc_start_main+0xe6) [0x275bd6]
13: /usr/bin/X (0x8048000+0x1e961) [0x8066961]
Segmentation fault at address 0xb5f64ffc
Caught signal 11 (Segmentation fault). Server aborting
ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: xorg 1:7.5+5ubuntu1
ProcVersionSignature: Ubuntu 2.6.32-24.38-generic 2.6.32.15+drm33.5
Uname: Linux 2.6.32-24-generic i686
Architecture: i386
Date: Thu Jul 29 09:07:06 2010
DkmsStatus: Error: [Errno 2] No such file or directory
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
MachineType: Sony Corporation VGN-C190G
PccardctlIdent:
Socket 0:
no product info available
PccardctlStatus:
Socket 0:
no card
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-24-generic root=UUID=0cb9888d-ddc8-4080-bd8b-4f36fdee854a ro quiet splash
ProcEnviron:
LANG=en_US.utf8
SHELL=/bin/bash
SourcePackage: xorg
dmi.bios.date: 09/16/2006
dmi.bios.vendor: Phoenix Technologies LTD
dmi.bios.version: R0030J4
dmi.board.asset.tag: N/A
dmi.board.name: VAIO
dmi.board.vendor: Sony Corporation
dmi.board.version: N/A
dmi.chassis.asset.tag: N/A
dmi.chassis.type: 10
dmi.chassis.vendor: Sony Corporation
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnPhoenixTechnologiesLTD:bvrR0030J4:bd09/16/2006:svnSonyCorporation:pnVGN-C190G:pvrR5216375:rvnSonyCorporation:rnVAIO:rvrN/A:cvnSonyCorporation:ct10:cvrN/A:
dmi.product.name: VGN-C190G
dmi.product.version: R5216375
dmi.sys.vendor: Sony Corporation
system:
distro: Ubuntu
codename: lucid
architecture: i686
kernel: 2.6.32-24-generic
[lspci]
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller [8086:27a2] (rev 03)
Subsystem: Sony Corporation Device [104d:820f]
Okay, let me try again.
The problem here is that a segfault in a KDE program, which is not run in a KDE desktop enviroment, is not caught by the KDE or GNOME crash handlers and thus the entire user session simply logs out immediately (which I believe is mediated by X).
I think I'm going to have to file this bug for the KDE crash handler, not X server.