Semaphore is a generalization of mutual exclusion locks. It allows at most N threads into critical section. Simple Semaphore uses a state field to keep track of the number of threads currently in CS, and is limited to a fixed capacity. A common lock is used for ensuring field updates are atomic, and a condition object is used for synchronization.
Acquiring the semaphore involves holding the common lock, waiting until the CS is not full, and incrementing the number of threads in CS before releasing the common lock.
Releasing the semaphore involves holding the common lock, decrementing the number of threads in CS, and signalling that CS is not full before releasing the common lock.
Java already provides a Semaphore. This is for educational purposes only.
Course: Concurrent Data Structures, Monsoon 2020
Taught by: Prof. Govindarajulu Regeti
acquire():
1. Acquire common lock.
2. Wait until CS is not full.
3. Increment number of threads in CS.
4. Release common lock.release():
1. Acquire common lock.
2. Decrement number of threads in CS.
3. Signal that CS is not full.
4. Release common lock.See SimpleSemaphore.java for code, Main.java for test, and repl.it for output.