java多线程死锁 Java线程堆栈分析

不知觉间工作已有一年了，闲下来的时候总会思考下，作为一名Java程序员，不能一直停留在开发业务使用框架上面。java多线程死锁老话说得好，机会是留给有准备的人的，因此，开始计划看一些Java底层一点的东西，尝试开始在学习的过程中写博客，希望和大家一起交流学习。

写在前面： 线程堆栈应该是多线程类应用程序非功能问题定位的最有效手段，可以说是杀手锏。线程堆栈最擅长与分析如下类型问题：

系统无缘无故CPU过高。

系统挂起，无响应。

系统运行越来越慢。

性能瓶颈（如无法充分利用CPU等）

线程死锁、死循环，饿死等。

由于线程数量太多导致系统失败（如无法创建线程等）。

如下面一段Java源代码程序：

package org.ccgogoing.study.stacktrace;
/** 
 * @Author: LuoChong400
 * @Description: 测试线程
 * @Date: Create in 07:27 PM 2017/12/08
 */
public class MyTest {

        Object obj1 = new Object();
        Object obj2 = new Object();

        public void fun1() {
            synchronized (obj1) {
                fun2();
            }
        }
        public void fun2() {
            synchronized (obj2) {
                while (true) { //为了打印堆栈，该函数堆栈分析不退出
                    System.out.print("");
                }
            }
        }
        public static void main(String[] args) {
            MyTest aa = new MyTest();
            aa.fun1();
        }
    }

在Idea 中运行该程序，然后按下CTRL+BREAK键，打印出线程堆栈信息如下：

Full thread dump Java HotSpot(TM) 64-Bit Server VM (24.79-b02 mixed mode):

"Service Thread" daemon prio=6 tid=0x000000000c53b000 nid=0xca58 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" daemon prio=10 tid=0x000000000c516000 nid=0xd390 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" daemon prio=10 tid=0x000000000c515000 nid=0xcbac waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Monitor Ctrl-Break" daemon prio=6 tid=0x000000000c514000 nid=0xd148 runnable [0x000000000caee000]
   java.lang.Thread.State: RUNNABLE
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.read(SocketInputStream.java:152)
    at java.net.SocketInputStream.read(SocketInputStream.java:122)
    at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:283)
    at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:325)
    at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:177)
    - locked <0x00000000d7858b50> (a java.io.InputStreamReader)
    at java.io.InputStreamReader.read(InputStreamReader.java:184)
    at java.io.BufferedReader.fill(BufferedReader.java:154)
    at java.io.BufferedReader.readLine(BufferedReader.java:317)
    - locked <0x00000000d7858b50> (a java.io.InputStreamReader)
    at java.io.BufferedReader.readLine(BufferedReader.java:382)
    at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)

"Attach Listener" daemon prio=10 tid=0x000000000ad4a000 nid=0xd24c runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" daemon prio=10 tid=0x000000000c1a8800 nid=0xd200 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" daemon prio=8 tid=0x000000000ace6000 nid=0xcd74 in Object.wait() [0x000000000c13f000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00000000d7284858> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
    - locked <0x00000000d7284858> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
    at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)

"Reference Handler" daemon prio=10 tid=0x000000000ace4800 nid=0xce34 in Object.wait() [0x000000000bf4f000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00000000d7284470> (a java.lang.ref.Reference$Lock)
    at java.lang.Object.wait(Object.java:503)
    at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)
    - locked <0x00000000d7284470> (a java.lang.ref.Reference$Lock)

"main" prio=6 tid=0x000000000238e800 nid=0xc940 runnable [0x00000000027af000]
   java.lang.Thread.State: RUNNABLE
    at org.ccgogoing.study.stacktrace.MyTest.fun2(MyTest.java:22)
    - locked <0x00000000d77d50c8> (a java.lang.Object)
    at org.ccgogoing.study.stacktrace.MyTest.fun1(MyTest.java:15)
    - locked <0x00000000d77d50b8> (a java.lang.Object)
    at org.ccgogoing.study.stacktrace.MyTest.main(MyTest.java:29)

"VM Thread" prio=10 tid=0x000000000ace1000 nid=0xd0a8 runnable 

"GC task thread#0 (ParallelGC)" prio=6 tid=0x00000000023a4000 nid=0xd398 runnable 

"GC task thread#1 (ParallelGC)" prio=6 tid=0x00000000023a5800 nid=0xcc20 runnable 

"GC task thread#2 (ParallelGC)" prio=6 tid=0x00000000023a7000 nid=0xb914 runnable 

"GC task thread#3 (ParallelGC)" prio=6 tid=0x00000000023a9000 nid=0xd088 runnable 

"VM Periodic Task Thread" prio=10 tid=0x000000000c53f000 nid=0xc1b4 waiting on condition 

JNI global references: 138

Heap
 PSYoungGen      total 36864K, used 6376K [0x00000000d7280000, 0x00000000d9b80000, 0x0000000100000000)
  eden space 31744K, 20% used [0x00000000d7280000,0x00000000d78ba0d0,0x00000000d9180000)
  from space 5120K, 0% used [0x00000000d9680000,0x00000000d9680000,0x00000000d9b80000)
  to   space 5120K, 0% used [0x00000000d9180000,0x00000000d9180000,0x00000000d9680000)
 ParOldGen       total 83456K, used 0K [0x0000000085800000, 0x000000008a980000, 0x00000000d7280000)
  object space 83456K, 0% used [0x0000000085800000,0x0000000085800000,0x000000008a980000)
 PSPermGen       total 21504K, used 3300K [0x0000000080600000, 0x0000000081b00000, 0x0000000085800000)
  object space 21504K, 15% used [0x0000000080600000,0x0000000080939290,0x0000000081b00000)

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