Comment 6 for bug 974041

I have eventually found a way to obtain detailed debug info when X server crashing.
I am executing the following command from a text console:
sudo gdb -p $(pidof X) -batch -ex 'handle all nostop' -ex 'handle all pass' -ex 'handle 11 stop' -ex 'cont' -ex 'bt full' -ex 'cont' > ~/Xcrash.txt
Then I return back to the graphical session and try to trigger the crash.
I have collected already a few of such backtraces, and I am a bit surprised that apparently they ALL are VERY different.
In general, it seems as if KWin erases some important stuff that is further dereferenced in libdrm functions, and it is rather random which function will trigger the crash.