Comment # 1 on bug 943548 from Reg Proctor

Here's a workaround I figure out last night. Not a good one as it's just
disabling a driver feature but better than no workaround.

In /etc/X11/xorg.conf.d/50-device.conf put:

Section "Device"
        Identifier  "HD5870" # (replace with your own name)
        BusID       "PCI:7:0:0" # (replace with your system detail)
        Driver      "radeon"
        Option      "EnablePageFlip" "off" # Default is "on".
EndSection