Testing Harness

[GD Deepz]

Does anybody have a good test harness to test the lock/unlock sequence. What excatly are we looking for in the test? Is it that for every thread that goes into a wait mode, it must eventually get a lock otherwise its deadlocked. I wrote a simple test harness. There are five threads but some of the threads are getting deadlocked meaning, they never acquire a lock.

public class LockTesting extends Thread {
private static Data data1;
private static Data data2;

public static void main(String[] args) {
data1 = new Data(); //Is two data Data objects valid

// data2 = new Data();
LockTesting test1 = new LockTesting();
LockTesting test2 = new LockTesting();

LockTesting test3 = new LockTesting();

LockTesting test4 = new LockTesting();
LockTesting test5 = new LockTesting();

test1.start();
test2.start();

test3.start();

test4.start();
test5.start();


/* (non-Javadoc)
* @see java.lang.Runnable#run()
*/
public void run() {
long cookie1 = data1.lockRecord(1);
data1.updateRecord(1, null, cookie1);

}
}

[Anton Golovin]

Hi, GD! In the run method, the last line should be the unlock method. What is happening now is that some records never get unlocked, and the threads waiting on them wait forever.

[GD Deepz]

Hi Anton, tks for your reply. In fact I do have a unlock method that is invoked as such:

updataRecord(long recNo, String[] data, long lockCookie){
try { dao.updateDatabase(contractor); //persist to database
} finally {
unlock(recNo, lockCookie); // this unlocks the record
}
}

It goes like this; lock/updateRecord/unlock

Not sure why it is caught in a waiting mode.

[Mike Vess]

First of all i think you should update you test-program so that every thread do several updates of the record not just one.

while(continuetorunbooleanflag) {
   long cookie1 = data1.lockRecord(1);
   data1.updateRecord(1, null, cookie1);
}

Why are you calling unlock in the updateRecord method?

Now to your question of why some threads are deadlocked. The problem must be in the lock/unlock methods. These methods should be synchronized in some way and whenever you unlock a record you must notify other threads that may be waiting in the lock method.