jstack命令测试

jstack用于打印出给定的java进程ID或core file或远程调试服务的Java堆栈信息。

命令格式

Usage:
    jstack [-l] <pid>
        (to connect to running process) 连接活动进程
    jstack -F [-m] [-l] <pid>
        (to connect to a hung process) 连接阻塞进程
    jstack [-m] [-l] <executable> <core>
        (to connect to a core file)	可能是产生core dump的java可执行程序，连接core文件
    jstack [-m] [-l] [server_id@]<remote server IP or hostname>
        (to connect to a remote debug server)  连接远程服务器

Options:
    -F  to force a thread dump. Use when jstack <pid> does not respond (process is hung)
    -m  to print both java and native frames (mixed mode)
    -l  long listing. Prints additional information about locks
    -h or -help to print this help message

• pid 为需要打印配置信息的Java进程号
• -F当’jstack [-l] pid’没有相应的时候强制打印栈信息
• -l长列表. 打印关于锁的附加信息,例如属于java.util.concurrent的ownable synchronizers列表.
• -m打印java和native c/c++框架的所有栈信息.
• -h | -help打印帮助信息

使用示例 检查死锁

1. 运行一个产生死锁的程序

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;

/**
 * @author zxg
 */
public class TestDeadLock {
    
    

    private static ReentrantLock lock1 = new ReentrantLock();
    private static ReentrantLock lock2 = new ReentrantLock();

    public static void main(String[] args) {
    
    
        Thread t1 = new Thread(() -> {
    
    
            lock1.lock();
            System.out.println(Thread.currentThread().getName() + " get lock1");
            try {
    
    
                TimeUnit.SECONDS.sleep(1);
                System.out.println(Thread.currentThread().getName() + " try to get lock2");
                lock2.lock();
            } catch (InterruptedException e) {
    
    
                e.printStackTrace();
            } finally {
    
    
                lock1.unlock();
            }
        }, "thread1");
        Thread t2 = new Thread(() -> {
    
    
            lock2.lock();
            System.out.println(Thread.currentThread().getName() + " get lock2");
            try {
    
    
                TimeUnit.SECONDS.sleep(1);
                System.out.println(Thread.currentThread().getName() + " try to get lock1");
                lock1.lock();
            } catch (InterruptedException e) {
    
    
                e.printStackTrace();
            } finally {
    
    
                lock2.unlock();
            }
        }, "thread2");

        t1.start();
        t2.start();
    }
}

程序造成死锁没有停止。

2. 查看该java进程号
   Ctrl+Shift+Esc
   

3. 统计线程数
   jstack -l 7776 | grep 'java.lang.Thread.State' | wc -l
   

4. jstack查看输出