(In reply to Alan W. Irwin from comment #9)
> So the current lockup could be due to an entirely different bug than in the
> lockups I have encountered for the direct use case.

Yeah, that looks like an RCU or other core kernel issue, not directly related
to the graphics drivers (which as you say, aren't really being used in this
case).

Does idle=nomwait on the kernel command line help for any of these issues, by
any chance?

It's also worth making sure the motherboard BIOS is up to date.