urlyBird testing lock

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posted 19 years ago

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I have two versions of test script for testing locking.
One version finds the error. Other not.
There is no significant difference between the two.
I like to know why the two programs are showing the difference.

code for version 1

package test.ub.bean.lock;
 
import suncertify.db.Data;
 
public class LockTest implements Runnable{
    private int testPosition = 0;

public LockTest() {
super();
 
}
public static void main(String[] arg){
for(int i =0; i < 3; i++){
  LockTest test = new LockTest();
  Thread t = new Thread(test);
  test.testPosition = i;
  t.start();
}
}

public void run(){
try{
switch(testPosition){
case 0:
{
Data d1 = new Data();
System.out.println("Testing thread :"+ testPosition + " locking " + 1);
long l11 = d1.lock(1);
System.out.println("Testing thread :"+ testPosition + " locking " + 2);
long l21 = d1.lock(2);
System.out.println("Testing thread :"+ testPosition + " locking " + 3);
long l31 = d1.lock(3);
System.out.println("Testing thread :"+ testPosition + " locking " + 4);
long l41 = d1.lock(4);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 1);
d1.unlock(1, l11);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 2);
d1.unlock(2, l21);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 3);
d1.unlock(3, l31);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 4);
d1.unlock(4, l41);
}
break;
case 1:
{
Data d1 = new Data();
System.out.println("Testing thread :"+ testPosition + " locking " + 1);
long l11 = d1.lock(1);
System.out.println("Testing thread :"+ testPosition + " locking " + 2);
long l21 = d1.lock(2);
System.out.println("Testing thread :"+ testPosition + " locking " + 3);
long l31 = d1.lock(3);
System.out.println("Testing thread :"+ testPosition + " locking " + 4);
long l41 = d1.lock(4);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 1);
d1.unlock(1, l11);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 2);
d1.unlock(2, l21);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 3);
d1.unlock(3, l31);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 4);
d1.unlock(4, l41);
}
 
break;
case 2:
{
Data d1 = new Data();
System.out.println("Testing thread :"+ testPosition + " locking " + 1);
long l11 = d1.lock(1);
System.out.println("Testing thread :"+ testPosition + " locking " + 2);
long l21 = d1.lock(2);
System.out.println("Testing thread :"+ testPosition + " locking " + 3);
long l31 = d1.lock(3);
System.out.println("Testing thread :"+ testPosition + " locking " + 4);
long l41 = d1.lock(4);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 1);
d1.unlock(1, l11);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 2);
d1.unlock(2, l21);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 3);
d1.unlock(3, l31);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 4);
d1.unlock(4, l41);
}
break;
}
}catch(Throwable th){
System.out.print("Testing thread :"+ testPosition);
th.printStackTrace();
}
}
}

The out put for above code is

The second version of code just have changes as follows

public void run(){
try{
switch(testPosition){
case 0:
execute();
break;
case 1:
execute();
break;
case 2:
execute();
break;
}
}catch(Throwable th){
System.out.print("Testing thread :"+ testPosition);
th.printStackTrace();
}
}
public void execute()  throws Exception {
Data d1 = new Data();
System.out.println("Testing thread :"+ testPosition + " locking " + 1);
long l11 = d1.lock(1);
System.out.println("Testing thread :"+ testPosition + " locking " + 2);
long l21 = d1.lock(2);
System.out.println("Testing thread :"+ testPosition + " locking " + 3);
long l31 = d1.lock(3);
System.out.println("Testing thread :"+ testPosition + " locking " + 4);
long l41 = d1.lock(4);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 1);
d1.unlock(1, l11);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 2);
d1.unlock(2, l21);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 3);
d1.unlock(3, l31);
System.out.println("Testing thread :"+ testPosition + " unlocking " + 4);
d1.unlock(4, l41);
 
}

But this is not catching the error
The output follows

Please note code in case0, case1, case2 and execute are identical(cut and paste).
Reason for the failure of lock is in the way I use synchronization.
lock method is having synchronized modifier which is wrong. I should be synchronizing on a common object (like a collection of locks or a non duplicated/cloned single lock) to all threads.

Extremely curious :roll: to know the difference. I am not giving the lock or unlock details which may deviate attention. The lock acquiring event is not logged for the same reason.

Any help is appreciated.
[ April 14, 2005: Message edited by: jiju ka ]

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