Big reader locks

I guess the major difference is that this one disallows any concurrency between readers and writers. In RCU, my understanding is that readers always get a "consistent" structure for as long as they need. A writer can start preparing a new copy while readers are still active.

In this, it sounds like a writer must wait until all readers are truly finished. When mounting/unmounting, that sounds like a useful, stronger semantic.

Or am I missing something?