https://bugs.freedesktop.org/show_bug.cgi?id=79980
--- Comment #95 from farmboy0+freedesktop@googlemail.com --- Is there some way to debug this? Debug messages from the kernel/mesa/whatever to activate to find out what goes on with the radeon driver. Some /sys files to monitor or something?
Please let us help you fix this bug but for me at least it was always a complete deadlock with nothing in the logs to indicate what went wrong.