Created attachment 70939 [details]
Error state from debugfs immediately after the hang occured

X.org hangs when running video player (mplayer) or firefox when not starting both programs shortly after logging into graphical session. 

git bisect pointed towards
commit dabdfe021ab1e985e6566009c774fb03f14b568e
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Mar 26 10:10:27 2012 +0200

    drm/i915: Avoid using mappable space for relocation processing through the CPU
    
    We try to avoid writing the relocations through the uncached GTT, if the
    buffer is currently in the CPU write domain and so will be flushed out to
    main memory afterwards anyway. Also on SandyBridge we can safely write
    to the pages in cacheable memory, so long as the buffer is LLC mapped.
    In either of these cases, we therefore do not need to force the
    reallocation of the buffer into the mappable region of the GTT, reducing
    the aperture pressure.
    
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

as the culprit.

Undoing that commit on 3.6.8 works for me.

dmesg error:

[drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung                                                
[drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung                                                             [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
[drm:i915_reset] *ERROR* GPU hanging too fast, declaring wedged!
[drm:i915_reset] *ERROR* Failed to reset chip.

System Information:
Dell Latitude E5500
Debian stable running vanilla 3.6.8
mesa: 7.7.1
xf86-video-intel: 2.13.0
libdrm: 2.4.21

Not using SNA acceleration

lspci -vv for the gfx card:
00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) (prog-if 00 [VGA controller])
        Subsystem: Dell Device 0263
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 0
        Interrupt: pin A routed to IRQ 44
        Region 0: Memory at f6c00000 (64-bit, non-prefetchable) [size=4M]
        Region 2: Memory at e0000000 (64-bit, prefetchable) [size=256M]
        Region 4: I/O ports at efe8 [size=8]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
                Address: fee0300c  Data: 41e1
        Capabilities: [d0] Power Management version 3
                Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
        Kernel driver in use: i915

Hope that helps and thanks in advance.