Created attachment 121212 [details]
/sys/class/drm/card0/error content

Description:
system hangs for less than 10 seconds while firefox browsing (for now I have no way to reliably reproduce the bug).

Hardware:
Intel Pentium CPU B970 at Asus X501A.

Versions:
x11-drivers/xf86-video-intel-2.99.917-r2
x11-base/xorg-server-1.17.4
x11-libs/libdrm-2.4.66
media-libs/mesa-11.1.1
sys-kernel/gentoo-sources-4.4.0 (kernel)

Dmesg log:
[34222.082445] [drm] GPU HANG: ecode 6:-1:0x00000000, reason: Kicking stuck semaphore on render ring, action: continue
[34222.082449] [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
[34222.082450] [drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
[34222.082452] [drm] drm/i915 developers can then reassign to the right component if it's not a kernel issue.
[34222.082453] [drm] The gpu crash dump is required to analyze gpu hangs, so please always attach it.
[34222.082454] [drm] GPU crash dump saved to /sys/class/drm/card0/error
[34438.084796] [drm] GPU HANG: ecode 6:-1:0x00000000, reason: Kicking stuck semaphore on render ring, action: continue
[34442.081816] [drm] GPU HANG: ecode 6:-1:0x00000000, reason: Kicking stuck semaphore on render ring, action: continue
[34620.084001] [drm] GPU HANG: ecode 6:-1:0x00000000, reason: Kicking stuck semaphore on render ring, action: continue
[34624.083818] [drm] GPU HANG: ecode 6:-1:0x00000000, reason: Kicking stuck semaphore on render ring, action: continue