高并发之-死锁

死锁代码 

package com.zy.concurent;

public class DeadLock {

    public static void main(String[] args) {
        Object obj1 = new Object();
        Object obj2 = new Object();
        Thread thread1 = new Thread(new DeadLockRunalbe(obj1, obj2, 1, 2, true));
        thread1.setName("thread1");
        thread1.start();
        Thread thread2 = new Thread(new DeadLockRunalbe(obj1, obj2, 2, 1, false));
        thread2.setName("thread2");
        thread2.start();
    }

    /**
     * 线程死锁等待演示
     */
    public static class DeadLockRunalbe implements Runnable {
        Object object1;
        Object object2;
        int a, b;
        boolean flag;

        public DeadLockRunalbe(Object obj1, Object obj2, int a, int b, boolean flag) {
            this.object1 = obj1;
            this.object2 = obj2;
            this.a = a;
            this.b = b;
            this.flag = flag;
        }

        @Override
        public void run() {
            try {
                if (flag) synchronized (object1) {
                    Thread.sleep(100);
                    synchronized (object2) {
                        System.out.println(a + b);
                    }
                }
                else synchronized (object2) {
                    Thread.sleep(100);
                    synchronized (object1) {
                        System.out.println(a + b);
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

}

通过jstack查看死锁信息：

通过jps -l查看死锁的进程ID：

jstack -l 8932查看死锁进程：

E:\project\interview\src\main\java\com\zy\concurent>jstack -l 8932
2020-03-15 16:21:50
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.192-b12 mixed mode):

"DestroyJavaVM" #14 prio=5 os_prio=0 tid=0x00000000030a3800 nid=0x1184 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"thread2" #13 prio=5 os_prio=0 tid=0x000000001e7c1000 nid=0x4390 waiting for monitor entry [0x000000002038e000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at com.zy.concurent.DeadLock$SynAddRunalbe.run(DeadLock.java:45)
        - waiting to lock <0x000000076b0f7480> (a com.zy.concurent.DeadLock$Obj1)
        - locked <0x000000076b0f9548> (a com.zy.concurent.DeadLock$Obj2)
        at java.lang.Thread.run(Thread.java:748)

   Locked ownable synchronizers:
        - None

"thread1" #12 prio=5 os_prio=0 tid=0x000000001e7c0000 nid=0x728 waiting for monitor entry [0x000000002028f000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at com.zy.concurent.DeadLock$SynAddRunalbe.run(DeadLock.java:39)
        - waiting to lock <0x000000076b0f9548> (a com.zy.concurent.DeadLock$Obj2)
        - locked <0x000000076b0f7480> (a com.zy.concurent.DeadLock$Obj1)
        at java.lang.Thread.run(Thread.java:748)

   Locked ownable synchronizers:
        - None

"Service Thread" #11 daemon prio=9 os_prio=0 tid=0x000000001e636800 nid=0x46b8 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"C1 CompilerThread3" #10 daemon prio=9 os_prio=2 tid=0x000000001e640800 nid=0x4548 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"C2 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x000000001e63e000 nid=0x1a0c waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x000000001e63b000 nid=0x3b44 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x000000001e633000 nid=0x2120 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x000000001e602000 nid=0x3d88 runnable [0x000000001fb8e000]
   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 <0x000000076b24fa98> (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 <0x000000076b24fa98> (a java.io.InputStreamReader)
        at java.io.BufferedReader.readLine(BufferedReader.java:389)
        at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:61)

   Locked ownable synchronizers:
        - None

"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000000001e53c800 nid=0x40e4 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001e592800 nid=0x46f8 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

   Locked ownable synchronizers:
        - None

"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x000000000319a800 nid=0x4d4 in Object.wait() [0x000000001f88f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x000000076af88ed0> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
        - locked <0x000000076af88ed0> (a java.lang.ref.ReferenceQueue$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=2 tid=0x000000001e523000 nid=0x2754 in Object.wait() [0x000000001f78f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x000000076af86bf8> (a java.lang.ref.Reference$Lock)
        at java.lang.Object.wait(Object.java:502)
        at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
        - locked <0x000000076af86bf8> (a java.lang.ref.Reference$Lock)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)

   Locked ownable synchronizers:
        - None

"VM Thread" os_prio=2 tid=0x000000001e502800 nid=0x2014 runnable

"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00000000030b8800 nid=0x4524 runnable

"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00000000030ba000 nid=0x4568 runnable

"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00000000030bc000 nid=0x17c4 runnable

"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00000000030be800 nid=0x273c runnable

"GC task thread#4 (ParallelGC)" os_prio=0 tid=0x00000000030c0800 nid=0x3be0 runnable

"GC task thread#5 (ParallelGC)" os_prio=0 tid=0x00000000030c1800 nid=0x338c runnable

"GC task thread#6 (ParallelGC)" os_prio=0 tid=0x00000000030c5000 nid=0x514 runnable

"GC task thread#7 (ParallelGC)" os_prio=0 tid=0x00000000030c6000 nid=0x3f44 runnable

"GC task thread#8 (ParallelGC)" os_prio=0 tid=0x00000000030c7000 nid=0x24b4 runnable

"GC task thread#9 (ParallelGC)" os_prio=0 tid=0x00000000030c8800 nid=0x472c runnable

"VM Periodic Task Thread" os_prio=2 tid=0x000000001e660800 nid=0x44f8 waiting on condition

JNI global references: 12


Found one Java-level deadlock:
=============================
"thread2":
  waiting to lock monitor 0x000000001ce43728 (object 0x000000076b0f7480, a com.zy.concurent.DeadLock$Obj1),
  which is held by "thread1"
"thread1":
  waiting to lock monitor 0x000000001ce42288 (object 0x000000076b0f9548, a com.zy.concurent.DeadLock$Obj2),
  which is held by "thread2"

Java stack information for the threads listed above:
===================================================
"thread2":
        at com.zy.concurent.DeadLock$SynAddRunalbe.run(DeadLock.java:45)
        - waiting to lock <0x000000076b0f7480> (a com.zy.concurent.DeadLock$Obj1)
        - locked <0x000000076b0f9548> (a com.zy.concurent.DeadLock$Obj2)
        at java.lang.Thread.run(Thread.java:748)
"thread1":
        at com.zy.concurent.DeadLock$SynAddRunalbe.run(DeadLock.java:39)
        - waiting to lock <0x000000076b0f9548> (a com.zy.concurent.DeadLock$Obj2)
        - locked <0x000000076b0f7480> (a com.zy.concurent.DeadLock$Obj1)
        at java.lang.Thread.run(Thread.java:748)

Found 1 deadlock.

可以看到：

 java中几种工具的介绍：

jstack

jstack是java虚拟机自带的一种堆栈跟踪工具。

jstack用于生成java虚拟机当前时刻的线程快照。线程快照是当前java虚拟机内每一条线程正在执行的方法堆栈集合，生成线程快照的主要目的是定位线程出现长时间停顿的原因。如线程间死锁、死循环、请求外部资源导致长时间等待等。线程出现停顿的时候通过jstack来查看各个线程的调用堆栈，就知道没有响应的线程到底在后台做什么事情，或者等待什么资源。

常用命令：

jstack -l pid

jstack -m pid

jps:

java提供的一个显示当前所有java进程pid命令。适合在Linux/unix平台简单查看当前java进程的一些简单情况。

常用：jps -l