Can you provide a real example of a situation where mutual resource locking occurred in a system or life?

Deadlock is a situation where two or more processes (or threads) are waiting for resources held by each other, and none of them can continue.

A real-life example: two people walking towards each other in a narrow corridor, each yielding to the other, and neither wants to step back. As a result, they both stand still and cannot pass.

An example in Java programming:

Object resourceA = new Object();
Object resourceB = new Object();

Thread thread1 = new Thread(() -> {
    synchronized (resourceA) {
        try { Thread.sleep(100); } catch (InterruptedException e) {}
        synchronized (resourceB) {
            System.out.println("Thread 1 acquired both resources");
        }
    }
});

Thread thread2 = new Thread(() -> {
    synchronized (resourceB) {
        try { Thread.sleep(100); } catch (InterruptedException e) {}
        synchronized (resourceA) {
            System.out.println("Thread 2 acquired both resources");
        }
    }
});

thread1.start();
thread2.start();

Here, thread1 acquires resourceA and waits for resourceB, while thread2 does the opposite — resourceB and waits for resourceA. As a result, a deadlock occurs.