We can get the concept of deadlock inwikipedia.
The picture below gives a common scenario which leads to deadlock.
In this blog, I will share how to detect deadlock situation using JDK standard tool jstack.
First we have to write a Java program which will lead to Deadlock:
package thread;
public class DeadLockExample {
/*
* Thread 1: locked resource 1
Thread 2: locked resource 2
*/
public static void main(String[] args) {
final String resource1 = "ABAP";
final String resource2 = "Java";
// t1 tries to lock resource1 then resource2
Thread t1 = new Thread() {
public void run() {
synchronized (resource1) {
System.out.println("Thread 1: locked resource 1");
try {
Thread.sleep(100);
} catch (Exception e) {
}
synchronized (resource2) {
System.out.println("Thread 1: locked resource 2");
}
}
}
};
Thread t2 = new Thread() {
public void run() {
synchronized (resource2) {
System.out.println("Thread 2: locked resource 2");
try {
Thread.sleep(100);
} catch (Exception e) {
}
synchronized (resource1) {
System.out.println("Thread 2: locked resource 1");
}
}
}
};
t1.start();
t2.start();
}
}
Execute this program, you will get output:
Thread 2: locked resource 2
Then use command jps -l -m to list the process id of this deadlock program. In my example it is 51476:
Just type jstack + process id, and it will display all detailed information about deadlock:
Here the object 0x00000000d6f64988 and 0x00000000d6f649b8 represent the two resource String "ABAP" and "Java".
