My guess would be that the system restore checkpointing functionality ends up holding a lock by necessity while it manipulates internal state. It would be reall

My guess would be that the system restore checkpointing functionality ends up holding a lock by necessity while it manipulates internal state. It would be really hard to make that sort of algorithm lock-free and preserve data integrity guarantees - I certainly wouldn't want to be responsible for writing it. Obviously the lock shouldn't be held so long and so often though...