Gentoo's Bugzilla –
Attachment 406720 Details for
Bug 542328media-video/vlc-2.2.0 with USE="ffmpeg vaapi", x11-drivers/ati-drivers-14.12-r3 and CONFIG_PREEMPT_VOLUNTARY kernel: [fglrx:firegl_lock_free] *ERROR* lock was not held by 9! (*lock=0x00000000)