• Java --- 01Java死锁


    使用jstack检查死锁

    import java.util.concurrent.BrokenBarrierException;
    import java.util.concurrent.CyclicBarrier;
    
    public class MyDeadThread {
        public static Object o1 = new Object();
        public static Object o2 = new Object();
        public static void main(String[] args) {
            CyclicBarrier barrier = new CyclicBarrier(2);
            new Thread(()->{
               synchronized (o1){
                   try {
                       barrier.await();
                   } catch (InterruptedException e) {
                       e.printStackTrace();
                   } catch (BrokenBarrierException e) {
                       e.printStackTrace();
                   }
    //               latch.countDown();
    //               try {
    //                   latch.await();//此处不能这样用,latch是阻塞主线程的。应该用阻塞子线程的。
    //               } catch (InterruptedException e) {
    //                   e.printStackTrace();
    //               }
                   synchronized (o2){
                       System.out.println(Thread.currentThread().getName());
                   }
               }
            }).start();
            new Thread(()->{
                synchronized (o2){
                    try {
                        barrier.await();
                        int numberWaiting = barrier.getNumberWaiting();
                        int parties = barrier.getParties();
                        System.out.println("numberWaiting="+numberWaiting+"如果num为0说明barrier设计生效了");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    } catch (BrokenBarrierException e) {
                        e.printStackTrace();
                    }
                    synchronized (o1){
                        System.out.println(Thread.currentThread().getName());
                    }
                }
            }).start();
        }
    
    }
    

     jstack查看

    [root@master javatest]# jstack -l 2019
    2020-10-24 11:50:03
    Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.221-b11 mixed mode):
    
    "Attach Listener" #11 daemon prio=9 os_prio=0 tid=0x00007fd3f0001000 nid=0x809 waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
       Locked ownable synchronizers:
    	- None
    
    "DestroyJavaVM" #10 prio=5 os_prio=0 tid=0x00007fd418009000 nid=0x7e4 waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
       Locked ownable synchronizers:
    	- None
    
    "Thread-1" #9 prio=5 os_prio=0 tid=0x00007fd4180f7800 nid=0x7ee waiting for monitor entry [0x00007fd3f59bb000]
       java.lang.Thread.State: BLOCKED (on object monitor)
    	at MyDeadLock.lambda$main$1(MyDeadLock.java:43)
    	- waiting to lock <0x00000000f0a5baa8> (a java.lang.Object)
    	- locked <0x00000000f0a5bab8> (a java.lang.Object)
    	at MyDeadLock$$Lambda$2/135721597.run(Unknown Source)
    	at java.lang.Thread.run(Thread.java:748)
    
       Locked ownable synchronizers:
    	- None
    
    "Thread-0" #8 prio=5 os_prio=0 tid=0x00007fd4180f5800 nid=0x7ed waiting for monitor entry [0x00007fd3f5abc000]
       java.lang.Thread.State: BLOCKED (on object monitor)
    	at MyDeadLock.lambda$main$0(MyDeadLock.java:26)
    	- waiting to lock <0x00000000f0a5bab8> (a java.lang.Object)
    	- locked <0x00000000f0a5baa8> (a java.lang.Object)
    	at MyDeadLock$$Lambda$1/1418481495.run(Unknown Source)
    	at java.lang.Thread.run(Thread.java:748)
    
       Locked ownable synchronizers:
    	- None
    
    "Service Thread" #7 daemon prio=9 os_prio=0 tid=0x00007fd4180b4000 nid=0x7eb runnable [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
       Locked ownable synchronizers:
    	- None
    
    "C1 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007fd4180b1000 nid=0x7ea waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
       Locked ownable synchronizers:
    	- None
    
    "C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007fd4180af000 nid=0x7e9 waiting on condition [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
       Locked ownable synchronizers:
    	- None
    
    "Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007fd4180ad000 nid=0x7e8 runnable [0x0000000000000000]
       java.lang.Thread.State: RUNNABLE
    
       Locked ownable synchronizers:
    	- None
    
    "Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007fd41807c000 nid=0x7e7 in Object.wait() [0x00007fd4086fd000]
       java.lang.Thread.State: WAITING (on object monitor)
    	at java.lang.Object.wait(Native Method)
    	- waiting on <0x00000000f0a08ed8> (a java.lang.ref.ReferenceQueue$Lock)
    	at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
    	- locked <0x00000000f0a08ed8> (a java.lang.ref.ReferenceQueue$Lock)
    	at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)
    	at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)
    
       Locked ownable synchronizers:
    	- None
    
    "Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007fd418077800 nid=0x7e6 in Object.wait() [0x00007fd4087fe000]
       java.lang.Thread.State: WAITING (on object monitor)
    	at java.lang.Object.wait(Native Method)
    	- waiting on <0x00000000f0a06c00> (a java.lang.ref.Reference$Lock)
    	at java.lang.Object.wait(Object.java:502)
    	at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
    	- locked <0x00000000f0a06c00> (a java.lang.ref.Reference$Lock)
    	at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
    
       Locked ownable synchronizers:
    	- None
    
    "VM Thread" os_prio=0 tid=0x00007fd41806e000 nid=0x7e5 runnable 
    
    "VM Periodic Task Thread" os_prio=0 tid=0x00007fd4180b7000 nid=0x7ec waiting on condition 
    
    JNI global references: 309
    
    
    Found one Java-level deadlock:
    =============================
    "Thread-1":
      waiting to lock monitor 0x00007fd3fc004e28 (object 0x00000000f0a5baa8, a java.lang.Object),
      which is held by "Thread-0"
    "Thread-0":
      waiting to lock monitor 0x00007fd3fc0062c8 (object 0x00000000f0a5bab8, a java.lang.Object),
      which is held by "Thread-1"
    
    Java stack information for the threads listed above:
    ===================================================
    "Thread-1":
    	at MyDeadLock.lambda$main$1(MyDeadLock.java:43)
    	- waiting to lock <0x00000000f0a5baa8> (a java.lang.Object)
    	- locked <0x00000000f0a5bab8> (a java.lang.Object)
    	at MyDeadLock$$Lambda$2/135721597.run(Unknown Source)
    	at java.lang.Thread.run(Thread.java:748)
    "Thread-0":
    	at MyDeadLock.lambda$main$0(MyDeadLock.java:26)
    	- waiting to lock <0x00000000f0a5bab8> (a java.lang.Object)
    	- locked <0x00000000f0a5baa8> (a java.lang.Object)
    	at MyDeadLock$$Lambda$1/1418481495.run(Unknown Source)
    	at java.lang.Thread.run(Thread.java:748)
    
    Found 1 deadlock.


      

    参考:
    https://docs.oracle.com/javase/8/docs/api/
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  • 原文地址:https://www.cnblogs.com/kltsee/p/13868282.html
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