System hangs, processes continue to run

[Chris]

Starting on 13 Sept last year the system would, to me, lockup however
background processes such as Fetchmail, Procmail, SpamAssassin and other
processes would continue to run as if nothing had happened. At the time
kernel 3.13.0-36-generic was in use. Also, this would appear in my
syslog - [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed...
render ring idle. This continued through all kernel iterations including
3.13.0-44. I've also had it happen when running 3.14.0-031400-generic
and by request from this bug report
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1402331 on 18 Jan I
installed kernel 3.19.0-031900rc5-generic as a test. The system 'hung'
on 19 Jan however the 'Hangcheck' issue was not present. Since then it's
'hung' at least 8 or more times each one without the 'Hangcheck..'
error. I've gone back to the current kernel, 3.13.0-44 and it 'hung'
again this morning. Each time it's after an uptime of approximately 2.5
- 3 days. I've been asked on the above bug report to do a 'kernel
bisection' which even though I've printed the instructions on this I'm
still a bit confused. I don't know where to go from here as the original
error is now no longer present.


Necessary info:

Ubuntu 14.04.1 LTS, Gnome 3.12.2, kernel 3.13.0-44-generic. Pertinent
output of sudo lshw below:

localhost                 
    description: Mini Tower Computer
    product: OptiPlex 780 ()
    vendor: Dell Inc.
    serial: G20PBM1
    width: 64 bits
    capabilities: smbios-2.5 dmi-2.5 vsyscall32
    configuration: administrator_password=enabled boot=normal
chassis=mini-tower power-on_password=enabled
uuid=44454C4C-3200-1030-8050-C7C04F424D31
  *-core
       description: Motherboard
       product: 0C27VV
       vendor: Dell Inc.
       physical id: 0
       version: A01
       serial: ..CN137400250867.
     *-firmware
          description: BIOS
          vendor: Dell Inc.
          physical id: 0
          version: A15
          date: 08/06/2013
          size: 64KiB
          capacity: 8128KiB
          capabilities: pci pnp apm upgrade shadowing escd cdboot
bootselect edd int13floppytoshiba int13floppy720 int5printscreen
int9keyboard int14serial int17printer acpi usb biosbootspecification
netboot
     *-cpu
          description: CPU
          product: Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz
          vendor: Intel Corp.
          physical id: 400
          bus info: cpu at 0
          slot: CPU
          size: 3GHz
          width: 64 bits
          clock: 1333MHz
          capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr
pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx
fxsr sse sse2 ss ht tm pbe syscall nx constant_tsc arch_perfmon pebs bts
rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3
cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
          configuration: cores=2 enabledcores=2 threads=2
        *-cache:0
             description: L1 cache
             physical id: 700
             size: 128KiB
             capacity: 128KiB
             capabilities: internal write-back unified
        *-cache:1
             description: L2 cache
             physical id: 701
             size: 6MiB
             capacity: 6MiB
             capabilities: internal varies unified
     *-memory
          description: System Memory
          physical id: 1000
          slot: System board or motherboard
          size: 4GiB
        *-bank:0
             description: DIMM DDR3 Synchronous 1066 MHz (0.9 ns)
             product: M378B5673EH1-CF8
             vendor: Samsung
             physical id: 0
             serial: 94C3C095
             slot: DIMM_1
             size: 2GiB
             width: 64 bits
             clock: 1066MHz (0.9ns)
        *-bank:1
             description: DIMM DDR3 Synchronous 1066 MHz (0.9 ns)
             product: M378B2873EH1-CF8
             vendor: Samsung
             physical id: 1
             serial: 76DE3D57
             slot: DIMM_3
             size: 1GiB
             width: 64 bits
             clock: 1066MHz (0.9ns)
        *-bank:2
             description: DIMM DDR3 Synchronous 1066 MHz (0.9 ns)
             product: M378B2873FHS-CF8
             vendor: Samsung
             physical id: 2
             serial: 76FE89C4
             slot: DIMM_2
             size: 1GiB
             width: 64 bits
             clock: 1066MHz (0.9ns)

-- 
Chris
KeyID 0xE372A7DA98E6705C
31.11°N 97.89°W (Elev. 1092 ft)
07:33:44 up 34 min, 1 user, load average: 0.83, 0.61, 0.50
Ubuntu 14.04.1 LTS, kernel 3.13.0-44-generic