Kernel TM and Checkpoints

Kernel STM

I was thining, from what I've read so far, it seems that transactional memory has been implemented purely at the hardware level or high up on the software level with objects - there is the word STM but doesn't really look practical.

Why not have it on the Kernel level? Apply same concepts as SLE and TLR there?

Checkpoints

One limitation in HTM is lack of resources and what to do when they run out, why not implement a checkpoint there? Similar to database checkpoints?

Or maybe it's called a rollback point? Will check it out...