(In reply to comment #6)
> I tried running a 3D game using the terminal to monitor stdout, and this was
> constantly spammed as well. Not sure if it gives any additional information.
> 
> radeon: Failed to allocate a buffer:
> radeon:    size      : 0 bytes
> radeon:    alignment : 4096 bytes
> radeon:    domains   : 4
> radeon:    flags     : 4

Yeah, pretty much the same message from userspace.

Looks like a bug in the userspace driver somewhere. Simplest thing to find it
would be to attach a debugger and get a backtrace when the message is printed.