System locks up, background operations continue running

[Chris]

Ubuntu 14.04.1 LTS, Gnome 3.12.2, kernel 3.19.0-031900rc5-generic (I'll
explain this later) 4Gb ram, Dell Optiplex 780, BIOS version A015. 

I placed extra information in the above because possibly some questions
on them may be asked. Starting in September of last year and
periodically continuing through 17 Jan the system would 'lockup' with
this in the syslog:

kernel: [173977.808008] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck
timer elapsed... render ring idle

There are two bug reports for this. One which I initiated at Ubuntu
Launchpad - https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1402331
and the other at 'freedesktop.org' which had already been initiated by
someone else - https://bugs.freedesktop.org/show_bug.cgi?id=75394 If you
take a look at the report on Launchpad you'll notice that firstly I was
told my BIOS needed updating. That I did with no change. I have since
been asked to do a 'kernel bisection' I've never done that before and to
be honest the meds I take screw me up most of the day and I haven't been
able to follow the directions very well. Be that as it may, I've
experienced this issue in kernel versions 3.13.., 3.14.. and now with
the 3.19 version however, there's been a change. No longer do I see the
'Hangcheck.....' entry in my syslog. Since 17 Jan I've had seven lockups
with no reason that I can see in my syslog. The reason I'm running the
3.19..kernel is that in the freedesktop.org report I was asked to
upgrade to the very latest kernel which happened to be the one above to
see if it made any difference. As far as background operations such as
Fetchmail, Procmail, SpamAssassin, ClamAV and so forth, they continue to
run as if nothing has happened. I can still move the mouse cursor around
still 'click' on something if it happens while on the web with Firefox
however nothing will happen and the clock which I have set to show
seconds will freeze.

If anyone has any suggestions on how to figure this out they would be
greatly appreciated. 

Chris

-- 
Chris
KeyID 0xE372A7DA98E6705C
31.11°N 97.89°W (Elev. 1092 ft)
07:08:43 up 11:53, 1 user, load average: 0.75, 0.98, 0.92
Ubuntu 14.04.1 LTS, kernel 3.19.0-031900rc5-generic