architectures that prevent freezing

. in a pre-emptive OS there should be no freezing;

given the new concurrency model

that includes the use of the graphics processor GPU

to do the system's non-graphics processing,

my current guess is that the freezes happen when

something goes wrong in the GPU,

and the CPU is just waiting forever .

. the CPU needs to have some way of getting control back,

and sending an exception message to

any of the processes that were affected by the hung-up GPU .

. could anybody at discussions.apple.com

correct this theory or comment on it ?