gdm crashes unexpectedly every now and then

[Peter Tenenbaum <peter.g.tenenbaum@gmail.com>]

Hi, everyone -- 

I've had 2 instances recently in which gdm unexpectedly crashed and restarted.  This morning, the log reported the following:

Aug 20 06:33:21 tibouchina kernel: [481166.096049] [drm:i915_gem_do_execbuffer] *ERROR* Failed to pin buffer 35 of 43, total 159727616 bytes: -28
Aug 20 06:33:21 tibouchina kernel: [481166.096053] [drm:i915_gem_do_execbuffer] *ERROR* 2020 objects [40 pinned], 399417344 object bytes [133828608 pinned], 133828608/234881024 gtt bytes
Aug 20 06:33:22 tibouchina gdm[1994]: WARNING: gdm_slave_xioerror_handler: Fatal X error - Restarting :0

Can anyone give me guidance about what the problem is and/or how to resolve it?

Thanks in advance,
-PT