Hi Paul,

You are beating me: I've just finished a my implementation, it's attached.
It boots with qemu, rcu torture enabled, both single and 8-cpu.

Two problems are open:
- right now, I don't use rcu_qsctr_inc() at all.
- qlowmark is set to 0, any other value breaks synchronize_rcu().

And I must read your implementation....

--
    Manfred