Two things. 1. A misplaced comma adds substantial confusion: "during a critical section, a thread may not block, or be pre-empted by the scheduler." This soun

Two things. 1. A misplaced comma adds substantial confusion: "during a critical section, a thread may not block, or be pre-empted by the scheduler." This sounds like the thread may not block OR if it's blocked, the scheduler would preempt it, which doesn't make sense in regarding to the readers using the critical section. It should read: "during a critical section, a thread may not block and it would NOT be preempted by the scheduler." That just means a thread in a critical section is guaranteed to run to the end of the critical section without worrying about other threads preempting it. It owns the processor until the end of the critical section. Then it makes sense. When the readers exit the critical section, they have done dealing with the old shared data. The writer's scheduled thread won't preempt the reader threads in critical section, and when it runs, it means the readers have finished. 2. Critical section is a form of lock. I don't see how it can be claimed lock-free. May be it should say critical section help avoid inter-processor locking.