虚拟线程的pinned问题终于被jdk25完美解决了

虚拟线程是一个非常有用的特征，但是JDK25以前，一直存在pinned问题，一些场景下会导致平台线程被占用无法释放。

比如下面的代码，在JDK 21下运行时，会卡住：

import java.time.Duration;
import java.util.concurrent.Executors;public class VirtualThreadPinningDemo {// 一个共享资源，我们将使用 synchronized 来保护它private static final Object sharedLock = new Object();public static void main(String[] args) {// 使用虚拟线程执行器创建大量虚拟线程try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {for (int i = 0; i < 100; i++) {int taskId = i;executor.submit(() -> performTask(taskId));}}System.out.println("All tasks completed.");}private static void performTask(int id) {System.out.printf("Task %d started on thread: %s%n", id, Thread.currentThread());// 情况1：在 synchronized 块内进行阻塞操作 -> 会导致 PINNEDsynchronized (sharedLock) {System.out.printf("Task %d acquired lock. Thread: %s%n", id, Thread.currentThread());try {// 模拟一个阻塞操作，比如睡眠或I/O// 在 synchronized 块内睡眠，虚拟线程无法被卸载，平台线程被占用！Thread.sleep(Duration.ofSeconds(2));} catch (InterruptedException e) {Thread.currentThread().interrupt();}System.out.printf("Task %d released lock.%n", id);}System.out.printf("Task %d finished.%n", id);}
}

　　运行结果：

Task 0 started on thread: VirtualThread[#30]/runnable@ForkJoinPool-1-worker-1
Task 0 acquired lock. Thread: VirtualThread[#30]/runnable@ForkJoinPool-1-worker-1
Task 1 started on thread: VirtualThread[#32]/runnable@ForkJoinPool-1-worker-10
Task 4 started on thread: VirtualThread[#35]/runnable@ForkJoinPool-1-worker-9
Task 5 started on thread: VirtualThread[#36]/runnable@ForkJoinPool-1-worker-5
Task 6 started on thread: VirtualThread[#37]/runnable@ForkJoinPool-1-worker-6
Task 7 started on thread: VirtualThread[#38]/runnable@ForkJoinPool-1-worker-8
Task 2 started on thread: VirtualThread[#33]/runnable@ForkJoinPool-1-worker-3
Task 8 started on thread: VirtualThread[#39]/runnable@ForkJoinPool-1-worker-7
Task 9 started on thread: VirtualThread[#40]/runnable@ForkJoinPool-1-worker-2
Task 10 started on thread: VirtualThread[#41]/runnable@ForkJoinPool-1-worker-4
Task 11 started on thread: VirtualThread[#42]/runnable@ForkJoinPool-1-worker-11
Task 12 started on thread: VirtualThread[#43]/runnable@ForkJoinPool-1-worker-13
Task 14 started on thread: VirtualThread[#45]/runnable@ForkJoinPool-1-worker-14
Task 13 started on thread: VirtualThread[#44]/runnable@ForkJoinPool-1-worker-12
Task 15 started on thread: VirtualThread[#46]/runnable@ForkJoinPool-1-worker-15
Task 16 started on thread: VirtualThread[#47]/runnable@ForkJoinPool-1-worker-16
Task 0 released lock.
Task 0 finished.
Task 17 started on thread: VirtualThread[#48]/runnable@ForkJoinPool-1-worker-1
这里就卡住不向下走了

　　

但是同样的代码，在JDK 25下，运行正常：

Task 2 started on thread: VirtualThread[#42]/runnable@ForkJoinPool-1-worker-3
Task 2 acquired lock. Thread: VirtualThread[#42]/runnable@ForkJoinPool-1-worker-3
Task 0 started on thread: VirtualThread[#37]/runnable@ForkJoinPool-1-worker-6
Task 3 started on thread: VirtualThread[#45]/runnable@ForkJoinPool-1-worker-6
Task 1 started on thread: VirtualThread[#39]/runnable@ForkJoinPool-1-worker-6
Task 4 started on thread: VirtualThread[#47]/runnable@ForkJoinPool-1-worker-6
Task 5 started on thread: VirtualThread[#48]/runnable@ForkJoinPool-1-worker-6
Task 7 started on thread: VirtualThread[#50]/runnable@ForkJoinPool-1-worker-6
Task 8 started on thread: VirtualThread[#53]/runnable@ForkJoinPool-1-worker-6
Task 9 started on thread: VirtualThread[#54]/runnable@ForkJoinPool-1-worker-6
Task 10 started on thread: VirtualThread[#55]/runnable@ForkJoinPool-1-worker-6
Task 11 started on thread: VirtualThread[#56]/runnable@ForkJoinPool-1-worker-6
Task 12 started on thread: VirtualThread[#57]/runnable@ForkJoinPool-1-worker-6
Task 13 started on thread: VirtualThread[#58]/runnable@ForkJoinPool-1-worker-6
Task 15 started on thread: VirtualThread[#60]/runnable@ForkJoinPool-1-worker-6
Task 16 started on thread: VirtualThread[#61]/runnable@ForkJoinPool-1-worker-6
Task 14 started on thread: VirtualThread[#59]/runnable@ForkJoinPool-1-worker-6
Task 17 started on thread: VirtualThread[#62]/runnable@ForkJoinPool-1-worker-6
Task 19 started on thread: VirtualThread[#64]/runnable@ForkJoinPool-1-worker-6
Task 18 started on thread: VirtualThread[#63]/runnable@ForkJoinPool-1-worker-6
Task 6 started on thread: VirtualThread[#49]/runnable@ForkJoinPool-1-worker-6
Task 21 started on thread: VirtualThread[#67]/runnable@ForkJoinPool-1-worker-6
Task 20 started on thread: VirtualThread[#66]/runnable@ForkJoinPool-1-worker-6
Task 22 started on thread: VirtualThread[#68]/runnable@ForkJoinPool-1-worker-6
Task 23 started on thread: VirtualThread[#69]/runnable@ForkJoinPool-1-worker-6
Task 24 started on thread: VirtualThread[#70]/runnable@ForkJoinPool-1-worker-6
Task 26 started on thread: VirtualThread[#72]/runnable@ForkJoinPool-1-worker-6
Task 25 started on thread: VirtualThread[#71]/runnable@ForkJoinPool-1-worker-6
Task 27 started on thread: VirtualThread[#73]/runnable@ForkJoinPool-1-worker-6
Task 28 started on thread: VirtualThread[#74]/runnable@ForkJoinPool-1-worker-3
Task 31 started on thread: VirtualThread[#77]/runnable@ForkJoinPool-1-worker-7
Task 30 started on thread: VirtualThread[#76]/runnable@ForkJoinPool-1-worker-7
Task 32 started on thread: VirtualThread[#78]/runnable@ForkJoinPool-1-worker-7
Task 29 started on thread: VirtualThread[#75]/runnable@ForkJoinPool-1-worker-7
Task 33 started on thread: VirtualThread[#79]/runnable@ForkJoinPool-1-worker-7
Task 34 started on thread: VirtualThread[#80]/runnable@ForkJoinPool-1-worker-7
Task 35 started on thread: VirtualThread[#81]/runnable@ForkJoinPool-1-worker-7
Task 36 started on thread: VirtualThread[#82]/runnable@ForkJoinPool-1-worker-7
Task 37 started on thread: VirtualThread[#83]/runnable@ForkJoinPool-1-worker-7
Task 38 started on thread: VirtualThread[#84]/runnable@ForkJoinPool-1-worker-7
Task 39 started on thread: VirtualThread[#85]/runnable@ForkJoinPool-1-worker-7
Task 41 started on thread: VirtualThread[#87]/runnable@ForkJoinPool-1-worker-7
Task 42 started on thread: VirtualThread[#88]/runnable@ForkJoinPool-1-worker-7
Task 40 started on thread: VirtualThread[#86]/runnable@ForkJoinPool-1-worker-7
Task 43 started on thread: VirtualThread[#89]/runnable@ForkJoinPool-1-worker-7
Task 44 started on thread: VirtualThread[#90]/runnable@ForkJoinPool-1-worker-7
Task 45 started on thread: VirtualThread[#91]/runnable@ForkJoinPool-1-worker-7
Task 46 started on thread: VirtualThread[#92]/runnable@ForkJoinPool-1-worker-7
Task 47 started on thread: VirtualThread[#93]/runnable@ForkJoinPool-1-worker-7
Task 48 started on thread: VirtualThread[#94]/runnable@ForkJoinPool-1-worker-7
Task 49 started on thread: VirtualThread[#95]/runnable@ForkJoinPool-1-worker-7
Task 50 started on thread: VirtualThread[#96]/runnable@ForkJoinPool-1-worker-7
Task 51 started on thread: VirtualThread[#97]/runnable@ForkJoinPool-1-worker-7
Task 52 started on thread: VirtualThread[#98]/runnable@ForkJoinPool-1-worker-7
Task 53 started on thread: VirtualThread[#99]/runnable@ForkJoinPool-1-worker-7
Task 54 started on thread: VirtualThread[#100]/runnable@ForkJoinPool-1-worker-7
Task 55 started on thread: VirtualThread[#101]/runnable@ForkJoinPool-1-worker-7
Task 56 started on thread: VirtualThread[#102]/runnable@ForkJoinPool-1-worker-7
Task 58 started on thread: VirtualThread[#104]/runnable@ForkJoinPool-1-worker-7
Task 59 started on thread: VirtualThread[#105]/runnable@ForkJoinPool-1-worker-7
Task 57 started on thread: VirtualThread[#103]/runnable@ForkJoinPool-1-worker-7
Task 60 started on thread: VirtualThread[#106]/runnable@ForkJoinPool-1-worker-7
Task 62 started on thread: VirtualThread[#108]/runnable@ForkJoinPool-1-worker-7
Task 63 started on thread: VirtualThread[#109]/runnable@ForkJoinPool-1-worker-7
Task 61 started on thread: VirtualThread[#107]/runnable@ForkJoinPool-1-worker-7
Task 64 started on thread: VirtualThread[#110]/runnable@ForkJoinPool-1-worker-7
Task 66 started on thread: VirtualThread[#112]/runnable@ForkJoinPool-1-worker-7
Task 65 started on thread: VirtualThread[#111]/runnable@ForkJoinPool-1-worker-7
Task 67 started on thread: VirtualThread[#113]/runnable@ForkJoinPool-1-worker-7
Task 68 started on thread: VirtualThread[#114]/runnable@ForkJoinPool-1-worker-7
Task 69 started on thread: VirtualThread[#115]/runnable@ForkJoinPool-1-worker-7
Task 70 started on thread: VirtualThread[#116]/runnable@ForkJoinPool-1-worker-7
Task 71 started on thread: VirtualThread[#117]/runnable@ForkJoinPool-1-worker-7
Task 72 started on thread: VirtualThread[#118]/runnable@ForkJoinPool-1-worker-7
Task 73 started on thread: VirtualThread[#119]/runnable@ForkJoinPool-1-worker-7
Task 74 started on thread: VirtualThread[#120]/runnable@ForkJoinPool-1-worker-7
Task 75 started on thread: VirtualThread[#121]/runnable@ForkJoinPool-1-worker-7
Task 76 started on thread: VirtualThread[#122]/runnable@ForkJoinPool-1-worker-7
Task 77 started on thread: VirtualThread[#123]/runnable@ForkJoinPool-1-worker-7
Task 78 started on thread: VirtualThread[#124]/runnable@ForkJoinPool-1-worker-7
Task 79 started on thread: VirtualThread[#125]/runnable@ForkJoinPool-1-worker-7
Task 80 started on thread: VirtualThread[#126]/runnable@ForkJoinPool-1-worker-7
Task 81 started on thread: VirtualThread[#127]/runnable@ForkJoinPool-1-worker-7
Task 82 started on thread: VirtualThread[#128]/runnable@ForkJoinPool-1-worker-7
Task 83 started on thread: VirtualThread[#129]/runnable@ForkJoinPool-1-worker-7
Task 84 started on thread: VirtualThread[#130]/runnable@ForkJoinPool-1-worker-7
Task 85 started on thread: VirtualThread[#131]/runnable@ForkJoinPool-1-worker-7
Task 86 started on thread: VirtualThread[#132]/runnable@ForkJoinPool-1-worker-7
Task 88 started on thread: VirtualThread[#134]/runnable@ForkJoinPool-1-worker-7
Task 87 started on thread: VirtualThread[#133]/runnable@ForkJoinPool-1-worker-7
Task 89 started on thread: VirtualThread[#135]/runnable@ForkJoinPool-1-worker-7
Task 90 started on thread: VirtualThread[#136]/runnable@ForkJoinPool-1-worker-7
Task 91 started on thread: VirtualThread[#137]/runnable@ForkJoinPool-1-worker-7
Task 92 started on thread: VirtualThread[#138]/runnable@ForkJoinPool-1-worker-7
Task 93 started on thread: VirtualThread[#139]/runnable@ForkJoinPool-1-worker-7
Task 94 started on thread: VirtualThread[#140]/runnable@ForkJoinPool-1-worker-7
Task 95 started on thread: VirtualThread[#141]/runnable@ForkJoinPool-1-worker-8
Task 97 started on thread: VirtualThread[#143]/runnable@ForkJoinPool-1-worker-8
Task 96 started on thread: VirtualThread[#142]/runnable@ForkJoinPool-1-worker-8
Task 98 started on thread: VirtualThread[#144]/runnable@ForkJoinPool-1-worker-3
Task 99 started on thread: VirtualThread[#145]/runnable@ForkJoinPool-1-worker-3
Task 2 released lock.
Task 2 finished.
Task 0 acquired lock. Thread: VirtualThread[#37]/runnable@ForkJoinPool-1-worker-7
Task 0 released lock.
Task 0 finished.
Task 3 acquired lock. Thread: VirtualThread[#45]/runnable@ForkJoinPool-1-worker-5
Task 3 released lock.
Task 3 finished.
Task 1 acquired lock. Thread: VirtualThread[#39]/runnable@ForkJoinPool-1-worker-7
Task 1 released lock.
Task 1 finished.
Task 4 acquired lock. Thread: VirtualThread[#47]/runnable@ForkJoinPool-1-worker-5
Task 4 released lock.
Task 4 finished.
Task 5 acquired lock. Thread: VirtualThread[#48]/runnable@ForkJoinPool-1-worker-7
Task 5 released lock.
Task 5 finished.
Task 7 acquired lock. Thread: VirtualThread[#50]/runnable@ForkJoinPool-1-worker-8
Task 7 released lock.
Task 7 finished.
Task 8 acquired lock. Thread: VirtualThread[#53]/runnable@ForkJoinPool-1-worker-8
Task 8 released lock.
Task 8 finished.
Task 9 acquired lock. Thread: VirtualThread[#54]/runnable@ForkJoinPool-1-worker-6
Task 9 released lock.
Task 9 finished.
Task 10 acquired lock. Thread: VirtualThread[#55]/runnable@ForkJoinPool-1-worker-8
Task 10 released lock.
Task 10 finished.
Task 11 acquired lock. Thread: VirtualThread[#56]/runnable@ForkJoinPool-1-worker-2
Task 11 released lock.
Task 11 finished.
Task 12 acquired lock. Thread: VirtualThread[#57]/runnable@ForkJoinPool-1-worker-8
Task 12 released lock.
Task 12 finished.
Task 13 acquired lock. Thread: VirtualThread[#58]/runnable@ForkJoinPool-1-worker-7
Task 13 released lock.
Task 13 finished.
Task 15 acquired lock. Thread: VirtualThread[#60]/runnable@ForkJoinPool-1-worker-7
Task 15 released lock.
Task 15 finished.
Task 16 acquired lock. Thread: VirtualThread[#61]/runnable@ForkJoinPool-1-worker-5
Task 16 released lock.
Task 16 finished.
Task 14 acquired lock. Thread: VirtualThread[#59]/runnable@ForkJoinPool-1-worker-2
Task 14 released lock.
Task 14 finished.
Task 17 acquired lock. Thread: VirtualThread[#62]/runnable@ForkJoinPool-1-worker-8
Task 17 released lock.
Task 17 finished.
Task 19 acquired lock. Thread: VirtualThread[#64]/runnable@ForkJoinPool-1-worker-8
Task 19 released lock.
Task 19 finished.
Task 18 acquired lock. Thread: VirtualThread[#63]/runnable@ForkJoinPool-1-worker-2
Task 18 released lock.
Task 18 finished.
... 会一直正常执行，直到运行结束

　　

附：不熟悉虚拟线程pinned问题的，可自行问deepseek