jstack + jdb command to view the thread deadlocks and stack information

If the program linked to death, sometimes used jstack view the thread information in the process, you need to add the parameter on -F, at this time if there is a deadlock information, it may not be printed deadlock stack information, use jdb, you can view the current deadlock thread operating stack.

As a simple simulation program deadlock

package com.demo.bootdemo;

import java.util.HashMap;
import java.util.Map;

import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;

@Component
public class MyListeners implements ApplicationListener<ContextRefreshedEvent> {

    private Map map = new HashMap<>();
    private String lock = "aa";

    @Override
    public void onApplicationEvent(ContextRefreshedEvent arg0) {

        Thread t = new Thread(new Runnable() {

            @Override
            public void run() {
                synchronized (map) {
                    System.out.println(Thread.currentThread().getName() + ": 获得map锁");
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    synchronized (lock) {
                        System.out.println(Thread.currentThread().getName() + ": 获得lock锁");    
                    }
                }
            }
        }, "t-1");

        Thread t2 = new Thread(new Runnable() {

            @Override
            public void run() {
                synchronized (lock) {
                    System.out.println(Thread.currentThread().getName() + ": 获得lock锁");
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    synchronized (map) {
                        System.out.println(Thread.currentThread().getName() + ": 获得map锁");    
                    }
                }
            }
        }, "t-2");
        
        t.start();
        t2.start();
    }

}

Get pid

Suppose the current virtual machine can not be connected directly to 27709, it is necessary to use parameter -F

Deadlock can be seen that the thread is not t-1 and t-2

Use jdb connection jvm

jdb -connect sun.jvm.hotspot.jdi.SAPIDAttachingConnector: pid = 27709

Execution threads command to get a list of all threads

Get Thread "t-1" stack information, as shown below, in conjunction with the analog deadlock code, it is easy to see where the problem

Similarly, the acquiring thread "t-2" stack information

Through the above steps, the code in question can be determined substantially.

The present embodiment is simply viewed under a rush document, there is no detailed look, added during a subsequent time, the following documents JDB

https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/tooldescr011.html#BABDHAHJ