How can a Spinlock mechanism be implemented for thread synchronization?

Spinlock is a synchronization mechanism where the thread attempting to acquire the lock does not enter a waiting (sleep) state but actively checks the lock's availability in a loop (busy-wait). This is effective if the wait time is short.

Methods of implementing Spinlock:

1. Using atomic operations — for example, compareAndSet or testAndSet on an atomic variable. The thread attempts to set a busy flag if it is free.

import java.util.concurrent.atomic.AtomicBoolean;

class SpinLock {
    private final AtomicBoolean lock = new AtomicBoolean(false);

    public void lock() {
        while (!lock.compareAndSet(false, true)) {
            // active wait
        }
    }

    public void unlock() {
        lock.set(false);
    }
}

2. Using low-level CPU primitives — for example, test_and_set or xchg instructions at the assembly level, which are implemented in Java via JNI or system code.

3. Using AtomicInteger or volatile variables with a loop to check and set the value.

4. Using LockSupport.parkNanos() inside the loop to reduce CPU load, combining spinlock with small pauses.

It is important to remember that Spinlock is suitable for short critical sections; otherwise, it can lead to excessive CPU load and reduced performance.