98 lines
2.2 KiB
Java
98 lines
2.2 KiB
Java
import java.util.LinkedList;
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import java.util.NoSuchElementException;
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import java.util.Queue;
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import java.util.concurrent.Semaphore;
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class WorkQueue {
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private volatile Queue<Task> tasks = new LinkedList<Task>();
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private Semaphore readSemaphore;
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private Semaphore writeSemaphore;
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private Semaphore generalAccessSemaphore;
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public WorkQueue(int maxSize) {
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readSemaphore = new Semaphore(0);
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writeSemaphore = new Semaphore(maxSize);
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generalAccessSemaphore = new Semaphore(1);
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}
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public void producer() throws InterruptedException {
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writeSemaphore.acquire();
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generalAccessSemaphore.acquire();
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Task t = new Task();
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tasks.add(t);
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readSemaphore.release();
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generalAccessSemaphore.release();
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}
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public void consumer() throws InterruptedException {
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Task t;
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readSemaphore.acquire();
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generalAccessSemaphore.acquire();
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// for some reason, consumer can get here without tasks in the list. how to fix?
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// -> adding general access semaphore fixed it :)
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if (tasks.isEmpty()) {
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// SHOULD never be reached
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System.out.println("!!! No tasks in the queue");
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return;
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}
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try {
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t = tasks.remove();
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} catch (NoSuchElementException e) {
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System.out.println("!!! No taks in queue (BUT STILL TRIED ACCESSING)");
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return;
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}
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writeSemaphore.release();
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generalAccessSemaphore.release();
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t.run();
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}
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public void printTaksSize() {
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System.out.println("Tasks in queue: " + tasks.size());
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}
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public static void main(String[] args) {
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WorkQueue w = new WorkQueue(10);
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Thread[] producers = new Thread[50];
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Thread[] consumers = new Thread[50];
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for (int i = 0; i < 50; i++) {
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producers[i] = new Thread(() -> {
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try {
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for (int j = 0; j < 100; j++) {
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w.producer();
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w.printTaksSize();
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Thread.sleep(100);
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}
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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}
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});
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consumers[i] = new Thread(() -> {
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try {
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for (int j = 0; j < 100; j++) {
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w.consumer();
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w.printTaksSize();
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Thread.sleep(100);
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}
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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}
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});
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producers[i].start();
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consumers[i].start();
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}
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}
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}
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class Task implements Runnable{
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public void run() {
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// System.out.println("Task is running");
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}
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} |