https://bugs.freedesktop.org/show_bug.cgi?id=85638
--- Comment #8 from Marco Boffo marcoboffo.waves@gmail.com --- (In reply to Marco Boffo from comment #7)
This problem seems vanished when I got the last kernel update: 3.17.2-1-ARCH.
Oh, it's not vanished. It happens only less times.