jstack命令详解

1、介绍

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，如果是在64位机器上，需要指定选项"-J-d64"，Windows的jstack使用方式只支持以下的这种方式：

jstack [-l] pid

如果java程序崩溃生成core文件，jstack工具可以用来获得core文件的java stack和native stack的信息，从而可以轻松地知道java程序是如何崩溃和在程序何处发生问题。另外，jstack工具还可以附属到正在运行的java程序中，看到当时运行的java程序的java stack和native stack的信息, 如果现在运行的java程序呈现hung的状态，jstack是非常有用的。

2、命令格式

jstack [ option ] pid
jstack [ option ] executable core
jstack [ option ] [server-id@]remote-hostname-or-IP

3、常用参数说明

1)、options：

executable Java executable from which the core dump was produced.

(可能是产生core dump的java可执行程序)

core 将被打印信息的core dump文件

remote-hostname-or-IP 远程debug服务的主机名或ip

server-id 唯一id,假如一台主机上多个远程debug服务

2）、基本参数：

-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

pid 需要被打印配置信息的java进程id,可以用jps查询.

4、jstack分析线程死锁

线程死锁的代码如下。

public class ThreadDeadLockDemo {
public static void main(String[] args) {
final Object obj_1 = new Object(), obj_2 = new Object();
Thread first = new Thread("first"){
@Override
public void run() {
synchronized (obj_1) {
try {
Thread.sleep(3000);
} catch (InterruptedException e) {}
synchronized (obj_2) {
System.out.println("first thread done.");
}
}
}
};
Thread second = new Thread("second"){
@Override
public void run() {
synchronized (obj_2) {
try {
Thread.sleep(3000);
} catch (InterruptedException e) {}
synchronized (obj_1) {
System.out.println("seconde thread done.");
}
}
}
};
first.start();
second.start();
}
}

执行程序，会引起线程死锁。

调用 jstack命令，查看当前进程的线程状态，打印信息如下。可以发现进程已经发生了死锁，first线程等待second线程释放资源，同时，second线程也在等待first线程释放资源。

Full thread dump Java HotSpot(TM) 64-Bit Server VM (20.45-b01 mixed mode):

"Attach Listener" daemon prio=10 tid=0x00007f87d0001000 nid=0x7c1 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

"DestroyJavaVM" prio=10 tid=0x00007f87fc005800 nid=0x793 waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

"second" prio=10 tid=0x00007f87fc0aa800 nid=0x7a1 waiting for monitor entry [0x00007f87fa5c1000]
java.lang.Thread.State: BLOCKED (on object monitor)
at ThreadDeadLockDemo$2.run(ThreadDeadLockDemo.java:10)
- waiting to lock <0x00000007d7036b40> (a java.lang.Object)
- locked <0x00000007d7036b50> (a java.lang.Object)

"first" prio=10 tid=0x00007f87fc0a8800 nid=0x7a0 waiting for monitor entry [0x00007f87fa6c2000]
java.lang.Thread.State: BLOCKED (on object monitor)
at ThreadDeadLockDemo$1.run(ThreadDeadLockDemo.java:10)
- waiting to lock <0x00000007d7036b50> (a java.lang.Object)
- locked <0x00000007d7036b40> (a java.lang.Object)

"Low Memory Detector" daemon prio=10 tid=0x00007f87fc08f800 nid=0x79e runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" daemon prio=10 tid=0x00007f87fc08d800 nid=0x79d waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" daemon prio=10 tid=0x00007f87fc08a800 nid=0x79c waiting on condition [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" daemon prio=10 tid=0x00007f87fc088800 nid=0x79b runnable [0x0000000000000000]
java.lang.Thread.State: RUNNABLE

"Finalizer" daemon prio=10 tid=0x00007f87fc06c000 nid=0x79a in Object.wait() [0x00007f87facc8000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d7001300> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118)
- locked <0x00000007d7001300> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:171)

"Reference Handler" daemon prio=10 tid=0x00007f87fc06a000 nid=0x799 in Object.wait() [0x00007f87fadc9000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000007d70011d8> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:485)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116)
- locked <0x00000007d70011d8> (a java.lang.ref.Reference$Lock)

"VM Thread" prio=10 tid=0x00007f87fc063800 nid=0x798 runnable

"GC task thread#0 (ParallelGC)" prio=10 tid=0x00007f87fc019000 nid=0x794 runnable

"GC task thread#1 (ParallelGC)" prio=10 tid=0x00007f87fc01a800 nid=0x795 runnable

"GC task thread#2 (ParallelGC)" prio=10 tid=0x00007f87fc01c800 nid=0x796 runnable

"GC task thread#3 (ParallelGC)" prio=10 tid=0x00007f87fc01e800 nid=0x797 runnable

"VM Periodic Task Thread" prio=10 tid=0x00007f87fc09a800 nid=0x79f waiting on condition

JNI global references: 882

Found one Java-level deadlock:
=============================
"second":
waiting to lock monitor 0x00007f87dc005f10 (object 0x00000007d7036b40, a java.lang.Object),
which is held by "first"
"first":
waiting to lock monitor 0x00007f87dc004b60 (object 0x00000007d7036b50, a java.lang.Object),
which is held by "second"

Java stack information for the threads listed above:
===================================================
"second":
at ThreadDeadLockDemo$2.run(ThreadDeadLockDemo.java:10)
- waiting to lock <0x00000007d7036b40> (a java.lang.Object)
- locked <0x00000007d7036b50> (a java.lang.Object)
"first":
at ThreadDeadLockDemo$1.run(ThreadDeadLockDemo.java:10)
- waiting to lock <0x00000007d7036b50> (a java.lang.Object)
- locked <0x00000007d7036b40> (a java.lang.Object)

Found 1 deadlock.