Version: TRUNK (using KDE Devel) Installed from: Compiled sources Compiler: GCC 4.2.1 OS: Linux When attempting to start KDE-4 with: "startkde" in an Xterm in an X session it fails with this error: xcb_xlib.c:50: xcb_xlib_unlock: Assertion c->xlib.lock failed After some Google research, I found this: http://osdir.com/ml/debian.devel.announce/2006-11/msg00010.html Ideally, you will not notice any change at all. However, Xlib/XCB includes some additional code to check for bugs in calling software. If you encounter a problem, you will most likely just see an application disappear, due to having triggered an assertion and aborted. If you ran the application from a terminal, you can look there to see error output and get more details; otherwise, look at ~/.xsession-errors. The assertions look like one of these: xcb_xlib.c:41: xcb_xlib_lock: Assertion `!c->xlib.lock' failed. xcb_xlib.c:50: xcb_xlib_unlock: Assertion `c->xlib.lock' failed. Both of these represent bugs in a caller of libX11, and *not* in libX11 or libxcb. The first assertion means that a caller attempted to lock the display while already locked. The second assertion means that a caller attempted to unlock the display without having it locked. If you encounter such bugs, please report a bug against the offending software (*not* libx11-6 or libxcb)
Created attachment 21760 [details] Log of attempt to run KDE 4 from Xterm IIUC, this is a KDE bug.
IMHO, this is a major bug.
To my knowledge neither KDE nor Qt lock the X connection, so this looks like a bug in some of the underlying libraries (including other X11 libraries, I suggest updating). Especially given that I don't see any such problem here.
Re: Comment #3 This seems quite possible. It is a known bug in Sun Java for instance. Do you think that the 'startkde' script should set: LIBXCB_ALLOW_SLOPPY_LOCK="true" and then we should consider the issue resolved?
I don't see why KDE should do that. More than just KDE is affected, and X libraries should not have affected backwards compatibility in such a bad way in the first place. I suggest asking your distribution to patch X libraries to merely issue a warning (like e.g. openSUSE does). If you can identify specific places in KDE which cause this problem, please report a bug for them, but I don't see this generic bugreport to be a KDE problem (especially given that in my KDE4 log there's not a single message about this, so this really looks like a problem in underlying libraries in your system).