jstack查看某个进程堆栈信息

jstack主要用来查看某个进程内线程的堆栈信息

一个死锁的模拟代码

package test;

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

/**
 * @className: test
 * @description: TODO 类描述
 * @author: mac
 * @date: 2020/12/3
 **/
public class test {
    public static Executor executor=Executors.newFixedThreadPool(5);
    public static Object lock=new Object();

    public static void main(String[] args) {
        Task task1=new Task();
        Task task2=new Task();
        executor.execute(task1);
        executor.execute(task2);
    }
    static class Task implements Runnable{

        @Override
        public void run() {
            synchronized (lock){
                calc();
            }
        }

        private void calc() {
            int n=0;
           for(;;){
               n++;
           }
        }
    }
}

top 查看系统中最耗资源的java进程pid

> top

3913 root      20   0 6751200  18888  10452 S 100.3  0.1   0:20.71 java                                                                   
 3494 root      20   0  750324  46036  16564 S   0.7  0.3  48:31.49 containerd                                                             
 4773 root      20   0  577428  33312  10540 S   0.7  0.2  77:03.92 jdog-kunlunmirr                                                        
23139 prometh+  20   0 1559032 117636  28908 S   0.7  0.7  32:40.89 prometheus                                                             
    1 root      20   0  191144   4132   2648 S   0.3  0.0  10:33.95 systemd              

找出上一步pid内最耗cpu的线程pid

> top -Hp 3913
  PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND                                                                 
 3929 root      20   0 6751200  18888  10452 R 99.7  0.1   0:59.54 java                                                                    
 3913 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3914 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.03 java                                                                    
 3915 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3916 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3917 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3918 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3919 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3920 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3922 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3923 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3924 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3925 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3926 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3927 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.00 java                                                                    
 3928 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.01 java                                                                    
 3930 root      20   0 6751200  18888  10452 S  0.0  0.1   0:00.01 java    

计算该线程的pid的十六进制

> printf "%x\n" 3929
f59

定位代码

> jstack 3913 | grep f59 -A 50
"pool-1-thread-1" #9 prio=5 os_prio=0 tid=0x00007f88bc100000 nid=0xf59 runnable [0x00007f88a8a42000]
   java.lang.Thread.State: RUNNABLE
        at test.test$Task.calc(test.java:35)
        at test.test$Task.run(test.java:28)
        - locked <0x000000076d45d8d8> (a java.lang.Object)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)

"Service Thread" #8 daemon prio=9 os_prio=0 tid=0x00007f88bc0da800 nid=0xf57 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C1 CompilerThread2" #7 daemon prio=9 os_prio=0 tid=0x00007f88bc0bd800 nid=0xf56 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007f88bc0bb800 nid=0xf55 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f88bc0b8800 nid=0xf54 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007f88bc0b7000 nid=0xf53 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007f88bc086000 nid=0xf52 in Object.wait() [0x00007f88a9149000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x000000076d408ee0> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
        - locked <0x000000076d408ee0> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216)

"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f88bc081800 nid=0xf50 in Object.wait() [0x00007f88a924a000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x000000076d406c00> (a java.lang.ref.Reference$Lock)
        at java.lang.Object.wait(Object.java:502)
        at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
        - locked <0x000000076d406c00> (a java.lang.ref.Reference$Lock)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)

"VM Thread" os_prio=0 tid=0x00007f88bc077800 nid=0xf4f runnable 

"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007f88bc01e800 nid=0xf4b runnable 

"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007f88bc020800 nid=0xf4c runnable 

"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007f88bc022000 nid=0xf4d runnable 

"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007f88bc024000 nid=0xf4e runnable 

在dump文件中,线程一般会存在下面几种状态

• RUNNABLE 线程处于执行中
• BLOCKED 线程被阻塞
• WAITING 线程正在等待