WindowServer eats CPU when monitor goes away

Number:rdar://9953462 Date Originated:15-Aug-2011 09:23 AM
Status:open Resolved:
Product:Mac OS X Product Version:10.7
Classification:Other Bug Reproducible:
Ever since Lion, my mini that is connected to a receiver & tv via HDMI has had odd behavior when the receiver/tv are turned off.  This usually only happens when an application like Plex is open when the 'monitor' goes away.  The WindowServer process will peg at 100% CPU unless I quit Plex.  Plex is full screen and doing some minor image transitions when sitting idle.

Steps to Reproduce:
1. Connect an HDMI mac mini to a receiver and TV
2. Boot everything up
3. Open Plex and make sure it's full screen
4. Disconnect or power off the receiver (switching inputs also severs the connection)
5. Login via ssh or other remote method to see WindowServer is going crazy at 100% CPU

Expected Results:
WindowServer should remain at it's typical low CPU usage

Actual Results:
WindowServer is at the top of the CPU usage with 100% usage.

I believe my old receiver didn't cause a complete disconnect, but my current receiver, a Denon 1910 I think, causes the monitor/audio HDMI device to basically go away when switching inputs or powering off.

This WindowServer issue might cause another bug I'm filing which is causing Screen Sharing to fail to properly work.  Screen sharing is at least not operating properly at this moment after a WindowServer CPU spike (until I ssh'd in and killed Plex & then WindowServer since it didn't calm back down)

Attached a sample of the WindowServer process during this issue.  I also forgot to mention that it's not just CPU usage that's the problem, I lose all ability to access the GUI.  The TV remains dark, screen sharing won't respond, attempts at getting it back up fail beyond a hard reboot. i can ssh in but telling it to reboot that way doesn't seem to finish.


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