Have you ever tried to run a graphical Java interface and ended up with an error stating "xlib.lock failed". Well, I have many times...
The error looks like this:
"xcb_xlib.c:50: xcb_xlib_unlock: Assertion `c->xlib.lock' failed"
Why this occurs I have no idea about and I tried to read and understand where it comes from but failed. There is a lot of confusion flying around different forums and articles but no one has really explained this in an understandable manner that I have found... Maybe only Linus Torvalds knows... ;)
Anyhow, the solution is quite simple, just fire the below in a terminal as the same user you try to trigger the Java app:
> export LIBXCB_ALLOW_SLOPPY_LOCK=1