使用LockSupport异常没有释放锁，导致死锁

蚰蜒螟2024-08-24 10:18

##死锁代码

复制代码

public class LockSupportThreadTest {

    public static void main(String[] args) {
        LockSupportThreadTest threadTest = new LockSupportThreadTest();
        Thread yym_user_thread2 = new Thread() {
            public void run() {
                LockSupport.park();
                System.out.println("yym_user_thread2");
                threadTest.resources(2);
            }
        };

        Thread yym_user_thread1 = new Thread() {
            public void run() {
                System.out.println("yym_user_thread1");
                threadTest.resources(0);
                LockSupport.unpark(yym_user_thread2);
            }
        };
        yym_user_thread1.setName("yym_user_thread1");
        yym_user_thread1.start();
        //
        Thread.yield();Thread.yield();Thread.yield();
        Thread.yield();Thread.yield();Thread.yield();
        yym_user_thread2.setName("yym_user_thread2");
        yym_user_thread2.start();
    }

    public void resources(int number) {
        int i = 10/number;
        System.out.println("resources"+i);
    }

}

##jstack查看死锁原因，yym_user_thread2没有其他线程唤醒

java 复制代码

"yym_user_thread2" #27 prio=5 os_prio=0 cpu=0.00ms elapsed=96.06s tid=0x0000022b79380000 nid=0x35784 waiting on condition  [0x00000070d84ff000]
   java.lang.Thread.State: WAITING (parking)
        at jdk.internal.misc.Unsafe.park(java.base@11.0.19/Native Method)
        at java.util.concurrent.locks.LockSupport.park(java.base@11.0.19/LockSupport.java:323)
        at com.newland.mi.thread.LockSupportThreadTest$1.run(LockSupportThreadTest.java:11)

##以上死锁产生原因，还是由于代码书写不规范产生。在finally释放锁

java 复制代码

try {
                    threadTest.resources(0);
                }finally {
                    LockSupport.unpark(yym_user_thread2);
                }