I noticed this behaviour in KDE since 4.10 and using the proprietary catalyst driver.
It only happens once in a while, and I couldn't find any info in the log files when it happened.

When I minimize a window or change it's size, my KDE session is killed and I land back in KDM. But as I said, it just happens once in a while.

The distribution doesn't really matter, and I even tried an older version of catalyst. No change.
It has to be a problem of KDE 4.10, because in 4.9 everything was fine.

What possible information could I provide to help pointing out the cause?

Try not using Catalyst. It's most likely the driver.

mgraesslin wrote:Try not using Catalyst. It's most likely the driver.

Hehe. I would like to, but the open source driver just leaves me graphical artifacts making it impossible to use.

That doesn't sound healthy: one driver causes X crashes and the other one creates visual garbage. What GPU is that? New or old? If it's a new one I'd recommend to stop using anything with OpenGL and try again with newer drivers. If it's an old GPU I would check for a hardware defect.

mgraesslin wrote:That doesn't sound healthy: one driver causes X crashes and the other one creates visual garbage. What GPU is that? New or old? If it's a new one I'd recommend to stop using anything with OpenGL and try again with newer drivers. If it's an old GPU I would check for a hardware defect.

It's an AMD APU (CPU with integrated GPU, rather new). It's definitely no hardware issue. The proprietary driver works on all other DE's.
But that's not important. I just gave the Radeon driver a new try, there was less artifacts than the last time I tried.
Next I followed the instructions from the Arch wiki: https://wiki.archlinux.org/index.php/AT ... logging_in

And I rebooted... even though the transparency of my Air themed panel is gone, I cannot see any artifacts anymore. (Well, only seldom when resizing Konsole) O_O
Guess, there were some fixes since I last checked. Awesome. Guess, we can call the case closed.

jovin wrote:even though the transparency of my Air themed panel is gone

which means you are no longer using OpenGL - no surprise the driver doesn't fail with that.

Btw. it's pretty irrelevant whether the problems do not occur in other DEs. KWin uses more of OpenGL if it is available than for example Compiz. The GPU is rather new and it's quite likely that the driver doesn't support what KWin uses. Especially Catalyst had been rather painful in the past for not supporting some of our (optional) requirements.

Try xrender compositing until the driver has better OpenGL support.

Also it's a basic rule that whenever X11 crashes (and you are back on KDM) it's an X11 bug (and in this context usually the GPU drivers fault - very seldom a libc issue, never any clients fault, that's like you browse to forum.kde.org and the server crashes - not your browsers or even your fault)

luebking wrote:Try xrender compositing until the driver has better OpenGL support.

Also it's a basic rule that whenever X11 crashes (and you are back on KDM) it's an X11 bug (and in this context usually the GPU drivers fault - very seldom a libc issue, never any clients fault, that's like you browse to forum.kde.org and the server crashes - not your browsers or even your fault)

I wouldn't be here if it would happen with other DEs, too.
So it can't be a problem with X11, if the other desktop environments just run fine.

That another software may not make a request to a broken function in the server does not mean the server or one of it's modules is not broken.

It's a very simple rule:
if X crashes it is by definition *always* a bug in X - X is not supposed to crash no matter what requests you make, even if your request parameters are wrong and utter nonsense. The client (ie. kwin) may crash, yes - but never X11.

Ask on the X11 mailing list or just google, if you don't trust me.

You'll also find the reason for the x11 crash in /var/log/Xorg.*.log - i bet your right arm it ends in fglrx.
Often it's (for fglrx) also just simply a misinstallation (you installed mesa and fglrx, which have binary incompatible GL libraries and the wrong driver uses the wrong library)