[OE-core] SetScene tasks hang forever?

[Rich Pixley]

I'm seeing a lot of builds apparently hanging forever, (the ones that 
work seem to work within seconds - the ones that hang seem to hang for 
at least 10's of minutes), with:

rich at dolphin> nice tail -f Log
MACHINE           = "qemux86"
DISTRO            = ""
DISTRO_VERSION    = "oe-core.0"
TUNE_FEATURES     = "m32 i586"
TARGET_FPU        = ""
meta              = "master:35b5fb2dd2131d4c7dc6635c14c6e08ea6926457"

NOTE: Resolving any missing task queue dependencies
NOTE: Preparing runqueue
NOTE: Executing SetScene Tasks

If I run top, I see one processor pinned at 98 - 99% utilization running 
python, but no other clues.

Can anyone point me to doc, explain what's going on here, or point me in 
the right direction to debug this?

--rich