https://bugs.freedesktop.org/show_bug.cgi?id=89876
--- Comment #1 from Michel Dänzer michel@daenzer.net --- (In reply to The Blue Troll from comment #0)
radeon: mmap failed, errno: 12
[...]
personal note: it might be possible it was a simple out of memory issue, as i did notice that ram useage was creeping up, but not sure.
Indeed, errno 12 is ENOMEM, so that was probably it.