JDK 24: added example of synchronize pinning virtual threads

Author: wesleyegberto

java-24/SynchronizeVirtualThreadTest.java

@@ -0,0 +1,47 @@
+import java.util.Scanner;
+import java.util.concurrent.Executors;
+
+/**
+ * Try to run in JDK 21 and 24.
+ * To run: `java -Djdk.virtualThreadScheduler.parallelism=2 -Djdk.tracePinnedThreads=short SynchronizeVirtualThreadTest.java`
+ */
+public class SynchronizeVirtualThreadTest {
+	public static void main(String[] args) {
+		// platform threads runs normally
+		// var executor = Executors.newFixedThreadPool(2);
+
+		// until Java 24, with parallelism 2, only two virtual thread will run by time
+		// the virtual threads gets pinned and blocked waiting forever
+		var factory = Thread.ofVirtual().name("VT-", 0).factory();
+		var executor = Executors.newThreadPerTaskExecutor(factory);
+
+		var riskOperation = new RiskOperation();
+
+		for (int i = 0; i < 5; i++) {
+			executor.submit(riskOperation::doSomething);
+		}
+
+		while (!executor.isTerminated()) {
+			;
+		}
+	}
+}
+
+class RiskOperation {
+	void doSomething() {
+		log("About to start a synchronized work");
+		this.doSynchronizedWork();
+		log("Work done");
+	}
+
+	synchronized void doSynchronizedWork() {
+		log("Doing synchronized work...");
+		try {
+			Thread.sleep(1_000);
+		} catch (InterruptedException ex) {}
+	}
+
+	void log(String message) {
+		System.out.printf("%s - %s%n", Thread.currentThread().toString(), message);
+	}
+}