In the first dependency ordering, B=1 doesn't really rely on A=1. Only actual dependency is that L can only be unlocked once both the writes are completed. Hence, these write operations can logically be executed concurrently and produce the same results as though they were executed sequentially.
Same goes for the reads x=A and y=B. These are independent of each other.
This comment was marked helpful 2 times.
fangyihua
This is showing that the program order does not need to strictly followed for a program to produce correct results. For example, as long as we run A=1 before we run Unlock(L), the correctness can be preserved. We don't necessarily need to follow A=1, B=1, Unlock(L). Some program order can be relaxed here.
In the first dependency ordering, B=1 doesn't really rely on A=1. Only actual dependency is that L can only be unlocked once both the writes are completed. Hence, these write operations can logically be executed concurrently and produce the same results as though they were executed sequentially. Same goes for the reads x=A and y=B. These are independent of each other.
This comment was marked helpful 2 times.
This is showing that the program order does not need to strictly followed for a program to produce correct results. For example, as long as we run A=1 before we run Unlock(L), the correctness can be preserved. We don't necessarily need to follow A=1, B=1, Unlock(L). Some program order can be relaxed here.
This comment was marked helpful 0 times.