com.apple.preference.displays.MirrorDisplays): Service only ran for 0 seconds. Grrrrrr.

I've had my Mac Pro 6,1 for a few months and noticed that the display crashes every few weeks, where the symptoms range from 1) screen is "frozen as-is", 2) while mouse cursor can move 3) Cannot click on anything on the screen. 4) System clock on screen is stuck at the time the displays froze, and 5) System is still responsive through SSH.

While there was some discussion on various boards about the issue being due to the AMD FirePro D500 and D700 cards, I have a pair of D300s in this unit, which aren't supposed to be impacted by the known Apple Issue.


This occurred again recently and after getting some time to dig into things further, I looked into /var/log/system.log file to see what was the most recent entries prior to the latest freeze episode.

Found the following:

Output snippet from /var/log/system.log
Apr  4 11:01:18 macpro com.apple.xpc.launchd[1] (com.apple.preference.displays.MirrorDisplays): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
Apr  4 11:01:28 macpro com.apple.xpc.launchd[1] (com.apple.preference.displays.MirrorDisplays): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
Apr  4 11:01:38 macpro com.apple.xpc.launchd[1] (com.apple.preference.displays.MirrorDisplays): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
Apr  4 11:01:58 macpro com.apple.xpc.launchd[1] (com.apple.preference.displays.MirrorDisplays): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
Apr  4 11:02:28 macpro com.apple.xpc.launchd[1] (com.apple.preference.displays.MirrorDisplays): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.


In digging around the web, found the above link on Stackexchange that talks about this issue being related to a particular issue with out an Apple plugin is behaving badly, and lists instructions on how to temporarily disable it:

Here's the overall steps taken:
Sourced from Stackechange article:
https://apple.stackexchange.com/questions/304745/mirrordisplays-error-every-30-seconds-in-system-log

1. Disable System Integrity Protection so you can edit the .plist file. Do this by rebooting into the recovery partition with cmd-R, open Terminal from the Utilities menu, and type:
   $ csrutil disable
2. Reboot, then edit the .plist file with this command:
   $ sudo vi /System/Library/LaunchAgents/com.apple.preference.displays.MirrorDisplays.plist
3. Comment out the line that causes the MirrorDisplays tool to load. Change this line:
      
4. To this:
   
5. Then, reboot and re-enable System Integrity Protection using the recovery partition as described above and type:
   $ csrutil enable
6. Reboot 

After implementing the changes, it appears that this has stopped the occurrence:

$ grep "MirrorDisplays): Service only ran" system.log | cut -d ':' -f1 | uniq -c

 164 Apr  4 11

 172 Apr  4 12

  47 Apr  4 13

   3 Apr  4 14

The above command is grepping the system.log for the event occurrence, then parsing based on the first colon ':' which filters out everything of the error past the Day and Hour. So the above output shows that at 11am it occurred 164 times, 12pm occurred 172 times, 1pm 47 and so on...

It's now almost 4pm and no occurrences since disabling!  Keeping fingers crossed that this will fix the freezing scenario, otherwise will continue trudging through the system.log file on the next freeze.