deadlock

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多线程

deadlock

死锁：线程1等待线程2互斥持有的资源，而线程2也在等待线程1互斥持有的资源，两个线程都无法继续执行。
活锁：线程持续重试一个总是失败的操作，导致无法继续执行
饿死：线程一直被调度器延迟访问其赖以执行的资源，也许是调度器先于低优先级的线程而执行高优先级的线程，同时总是会有一个高优先级
的线程可以执行，饿死也叫做无线延迟。

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public class MyTest6 {
    private Object lock1 = new Object();
    private Object lock2 = new Object();
    public void myMethod1() {
        synchronized (lock1) {
            synchronized (lock2) {
                System.out.println("myMethod1 invoked");
            }
        }
    }
    public void myMethod2() {
        synchronized (lock2) {
            synchronized (lock1) {
                System.out.println("myMethod2 invoked");
            }
        }
    }
    public static void main(String[] args) {
        MyTest6 myTest6 = new MyTest6();
        Runnable runnable1 = () ->{
            while (true) {
                myTest6.myMethod1();
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };
        Thread thread1 = new Thread(runnable1, "myThread1");
        Runnable runnable2 = () ->{
            while (true) {
                myTest6.myMethod2();
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };
        Thread thread2 = new Thread(runnable2, "myThread2");
        thread1.start();
        thread2.start();
    }
}

检测与相关工具

图形化工具

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2
jvisualvm

concurrency-1

concurrency-2

命令行

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jps
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11872 Main
10980 Jps
11844 Launcher
3060
11212 MyTest6
1
jstack 11212
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2019-12-12 14:44:39
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.131-b11 mixed mode):
"DestroyJavaVM" #13 prio=5 os_prio=0 tid=0x00000000031d2800 nid=0x3624 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
"myThread2" #12 prio=5 os_prio=0 tid=0x00000000194e3000 nid=0xd78 waiting for monitor entry [0x0000000019f9e000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at com.bob.concurrency3.MyTest6.myMethod2(MyTest6.java:37)
        - waiting to lock <0x00000000d5e9c078> (a java.lang.Object)
        - locked <0x00000000d5e9c088> (a java.lang.Object)
        at com.bob.concurrency3.MyTest6.lambda$main$1(MyTest6.java:62)
        at com.bob.concurrency3.MyTest6$$Lambda$2/1096979270.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:748)
"myThread1" #11 prio=5 os_prio=0 tid=0x00000000194de000 nid=0x3174 waiting for monitor entry [0x0000000019e9f000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at com.bob.concurrency3.MyTest6.myMethod1(MyTest6.java:27)
        - waiting to lock <0x00000000d5e9c088> (a java.lang.Object)
        - locked <0x00000000d5e9c078> (a java.lang.Object)
        at com.bob.concurrency3.MyTest6.lambda$main$0(MyTest6.java:49)
        at com.bob.concurrency3.MyTest6$$Lambda$1/1324119927.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:748)
"Service Thread" #10 daemon prio=9 os_prio=0 tid=0x00000000192bb000 nid=0x2cf4 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
"C1 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x000000001924f000 nid=0x2fa0 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
"C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x00000000191f5800 nid=0x3478 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
"C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x00000000191f2800 nid=0x3528 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
"Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x00000000191e6800 nid=0x3544 runnable [0x000000001989e000]
   java.lang.Thread.State: RUNNABLE
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
        at java.net.SocketInputStream.read(SocketInputStream.java:171)
        at java.net.SocketInputStream.read(SocketInputStream.java:141)
        at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
        at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
        at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
        - locked <0x00000000d5f34298> (a java.io.InputStreamReader)
        at java.io.InputStreamReader.read(InputStreamReader.java:184)
        at java.io.BufferedReader.fill(BufferedReader.java:161)
        at java.io.BufferedReader.readLine(BufferedReader.java:324)
        - locked <0x00000000d5f34298> (a java.io.InputStreamReader)
        at java.io.BufferedReader.readLine(BufferedReader.java:389)
        at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)
"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x0000000017e3e000 nid=0x3754 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x00000000191a8800 nid=0x10b8 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x0000000017e1a800 nid=0x14cc in Object.wait() [0x000000001919f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x00000000d5d08ec8> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
        - locked <0x00000000d5d08ec8> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x00000000032c0800 nid=0x3030 in Object.wait() [0x000000001909f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x00000000d5d06b68> (a java.lang.ref.Reference$Lock)
        at java.lang.Object.wait(Object.java:502)
        at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
        - locked <0x00000000d5d06b68> (a java.lang.ref.Reference$Lock)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
"VM Thread" os_prio=2 tid=0x0000000017df8000 nid=0x9f4 runnable
"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00000000031e7800 nid=0x37c8 runnable
"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00000000031e9800 nid=0x2794 runnable
"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00000000031eb000 nid=0x3024 runnable
"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00000000031ec800 nid=0x1154 runnable
"VM Periodic Task Thread" os_prio=2 tid=0x00000000192c6000 nid=0x3074 waiting on condition
JNI global references: 335
Found one Java-level deadlock:
=============================
"myThread2":
  waiting to lock monitor 0x00000000032c8b58 (object 0x00000000d5e9c078, a java.lang.Object),
  which is held by "myThread1"
"myThread1":
  waiting to lock monitor 0x00000000032c8aa8 (object 0x00000000d5e9c088, a java.lang.Object),
  which is held by "myThread2"
Java stack information for the threads listed above:
===================================================
"myThread2":
        at com.bob.concurrency3.MyTest6.myMethod2(MyTest6.java:37)
        - waiting to lock <0x00000000d5e9c078> (a java.lang.Object)
        - locked <0x00000000d5e9c088> (a java.lang.Object)
        at com.bob.concurrency3.MyTest6.lambda$main$1(MyTest6.java:62)
        at com.bob.concurrency3.MyTest6$$Lambda$2/1096979270.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:748)
"myThread1":
        at com.bob.concurrency3.MyTest6.myMethod1(MyTest6.java:27)
        - waiting to lock <0x00000000d5e9c088> (a java.lang.Object)
        - locked <0x00000000d5e9c078> (a java.lang.Object)
        at com.bob.concurrency3.MyTest6.lambda$main$0(MyTest6.java:49)
        at com.bob.concurrency3.MyTest6$$Lambda$1/1324119927.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:748)
Found 1 deadlock.