Can you explain how locking mechanics are implemented when using synchronized or lock in multithreaded programming?

The locking mechanism when using synchronized (in Java) or lock (in C#) is based on synchronization primitives that provide exclusive access to a critical section of code.

When a thread enters a block protected by lock or synchronized, it attempts to acquire the associated lock object (mutex). If the lock is free, the thread acquires it and continues execution. If the lock is already held by another thread, the current thread is blocked (waits) until the lock is released.

In C#, an example with lock:

private readonly object _lockObj = new object();

void CriticalSection() {
    lock(_lockObj) {
        // code that should only be executed by one thread at a time
    }
}

Inside lock, the compiler generates calls to Monitor.Enter and Monitor.Exit, which manage acquiring and releasing the lock.

Thus, the locking mechanism guarantees that only one thread executes the critical section at a time, preventing race conditions and ensuring data correctness.