1、Mutual exclusion

The flag and turn variables usage can satisfy this requirement. Only one process will succeed if two flag variables are both true. The turn variable is the same. Also only the turn variable is updated of another process can the waiting process step into its critical section.

2、Progress

The flag and turn variables usage can also meet this requirement. If a process intends to enter its critical section, it can set the flag variable true. If the same process intends