Created attachment 119293 [details]
/sys/class/drm/card0/error

After some upgrades (only graphics-related part was xserver-xorg-video-intel:i386 from 2:2.99.917-2 to 2:2.99.917+git20151019-1~exp1) I sterted to recieve random gpu hangs. Sometimes display become garbage and system hangs entirely (no reactio to alt-sysrq), some times garbage appears but all continues to work. Suspend/resume was never used.

Attached dump is from the "hangs but continues to work situation".

It crashed at night, nothing were done with computer. Window manager is awesome with server-side composition by "xcompmgr -a". Also hardware-accelerated chromium was running.

I'm using debian testing/expiremental with amd64 kernel and entirely 32-bit x86 userspace.

Kernel version: 
Linux 4.2.0-1-amd64 #1 SMP Debian 4.2.1-2 (2015-09-27) x86_64 GNU/Linux

lspci (part):
00:02.0 VGA compatible controller: Intel Corporation 82945G/GZ Integrated Graphics Controller (rev 02)

Xorg.0.log (part)

[    38.982] (II) intel(0): Using Kernel Mode Setting driver: i915, version 1.6.0 20150522
[    38.982] (II) intel(0): SNA compiled: xserver-xorg-video-intel 2:2.99.917+git20151019-1~exp1 (Timo Aaltonen <tjaalton@debian.org>)
[    38.982] (II) intel(0): SNA compiled for use with valgrind
[    39.052] (--) intel(0): Integrated Graphics Chipset: Intel(R) 945G
[    39.052] (--) intel(0): CPU: x86, sse2, sse3, ssse3; using a maximum of 2 threads
[    39.052] (II) intel(0): Creating default Display subsection in Screen section
        "Default Screen Section" for depth/fbbpp 24/32
[    39.052] (==) intel(0): Depth 24, (--) framebuffer bpp 32
[    39.052] (==) intel(0): RGB weight 888
[    39.052] (==) intel(0): Default visual is TrueColor
[    39.052] (**) intel(0): Option "AccelMethod" "sna"
[    39.054] (II) intel(0): Output VGA1 has no monitor section
[    39.054] (II) intel(0): Enabled output VGA1
[    39.054] (--) intel(0): Using a maximum size of 256x256 for hardware cursors
[    39.055] (II) intel(0): Output VIRTUAL1 has no monitor section
[    39.055] (II) intel(0): Enabled output VIRTUAL1
[    39.055] (--) intel(0): Output VGA1 using initial mode 1920x1200 on pipe 0
[    39.055] (==) intel(0): TearFree disabled
[    39.055] (==) intel(0): DPI set to (96, 96)
[    39.055] (II) Loading sub module "dri2"
[    39.056] (II) LoadModule: "dri2"
[    39.056] (II) Module "dri2" already built-in
[    39.056] (II) Loading sub module "present"
[    39.056] (II) LoadModule: "present"
[    39.056] (II) Module "present" already built-in
[    39.056] (==) Depth 24 pixmap format is 32 bpp
[    39.117] (II) intel(0): SNA initialized with Alviso (gen3) backend
[    39.117] (==) intel(0): Backing store enabled
[    39.117] (==) intel(0): Silken mouse enabled
[    39.137] (II) intel(0): HW Cursor enabled
[    39.137] (II) intel(0): RandR 1.2 enabled, ignore the following RandR disabled message.
[    39.144] (==) intel(0): DPMS enabled
[    39.144] (==) intel(0): Display hotplug detection enabled
[    39.167] (II) intel(0): [XvMC] i915_xvmc driver initialized.
[    39.168] (II) intel(0): [DRI2] Setup complete
[    39.168] (II) intel(0): [DRI2]   DRI driver: i915
[    39.168] (II) intel(0): [DRI2]   VDPAU driver: va_gl
[    39.168] (II) intel(0): direct rendering: DRI2 enabled
[    39.168] (II) intel(0): hardware support for Present enabled
[    39.168] (--) RandR disabled
[    39.213] (II) SELinux: Disabled on system
[    39.779] (II) AIGLX: enabled GLX_MESA_copy_sub_buffer
[    39.779] (II) AIGLX: enabled GLX_ARB_create_context
[    39.779] (II) AIGLX: enabled GLX_ARB_create_context_profile
[    39.779] (II) AIGLX: enabled GLX_EXT_create_context_es2_profile
[    39.779] (II) AIGLX: enabled GLX_INTEL_swap_event
[    39.779] (II) AIGLX: enabled GLX_SGI_swap_control and GLX_MESA_swap_control
[    39.779] (II) AIGLX: enabled GLX_EXT_framebuffer_sRGB
[    39.779] (II) AIGLX: enabled GLX_ARB_fbconfig_float
[    39.779] (II) AIGLX: GLX_EXT_texture_from_pixmap backed by buffer objects
[    39.780] (II) AIGLX: Loaded and initialized i915
[    39.780] (II) GLX: Initialized DRI2 GL provider for screen 0
[    39.807] (II) intel(0): switch to mode 1920x1200@60.0 on VGA1 using pipe 0, position (0, 0), rotation normal, reflection none
[    39.808] (II) intel(0): Setting screen physical size to 507 x 317

dmesg(all messages except boot):
[39710.792060] [drm] stuck on render ring
[39710.796710] [drm] GPU HANG: ecode 3:0:0x00bbf88a, in Xorg [1117], reason: Ring hung, action: reset
[39710.796719] [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
[39710.796722] [drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
[39710.796726] [drm] drm/i915 developers can then reassign to the right component if it's not a kernel issue.
[39710.796729] [drm] The gpu crash dump is required to analyze gpu hangs, so please always attach it.
[39710.796733] [drm] GPU crash dump saved to /sys/class/drm/card0/error
[39710.796941] drm/i915: Resetting chip after gpu hang

package versions of graphics-related apps:
libdrm-intel1/testing,now 2.4.64-1 i386
libdrm2/testing,now 2.4.64-1 i386 
xserver-xorg-video-intel/experimental,now 2:2.99.917+git20151019-1~exp
xserver-xorg-core/now 2:1.17.2-2 i386
xcompmgr/testing,unstable,now 1.1.7-1 i386
libglapi-mesa/now 11.0.0~rc1-1 i386
chromium/now 46.0.2490.13-1 i386
linux-image-4.2.0-1-amd64/now 4.2.1-2 amd64