B&S: Simplest locking successful?

[Volker Abel]

Hi there

I am currently working on the B&S locking strategy.

There is a simplistic approach to just synchronize all read and write methods in the Data class (server side) and implement wait/notify in the lock/unlock methods (with a Map recordId -> cookie).

Can one really score 80/80 Points using this approach (assuming it is implemented correctly of course)? Sounds too good to be true. No fancy ReentrantReadWriteLock fuss needed?

Somehow this appears "too simple" to me. And it means that you practically have a database lock because no two threads can execute methods of the Data class simultaneously.

Regards
Volker

[Volker Abel]

Hi,

maybe it was not clear what I meant with "simplest locking mechanism".

Pseudocode:

    // any access method is synchronized

    public synchronized void delete(int recNo, long lockCookie) ... {
        ...
    }

    public synchronized int[] find(String[] criteria) ... {
        ...
    }

    public synchronized String[] read(int recNo) ... {
        ...
    }

    public synchronized long lock(int recNo) ... {
	while (lockedRecords.get(recNo) != null) {
	    try {
		wait();
	    } catch (InterruptedException e) {
	    }
                    // generate new cookie and put it into map
	}
	return newCookie;
    }

    public synchronized void unlock(int recNo, long cookie) ... {
          // remove cookie from map
          notifyAll();
    }



    

Does anyone know about scoring 80/80 with this strategy?

VA

[K. Tsang]

I'm doing UB not B&S but I'm sure locking is locking. Synchronizing all methods may be the simplest but may NOT be the most effective. For me anyway, I use "critical section" and "read/write lock" design patterns for my Data class.

[Volker Abel]

K. Tsang , thanks for your reply. I agree that locking all methods is not the most effective. In a "real world" project this is very important. Here, the goal is different: score 80/80.

Would you say that efficiency a "must" for the assignment?

[K. Tsang]

Efficiency isn't the most important. But do need to consider code clarity and maintainability and of course the overall design. Of course making it work and not hang (eg getting deadlock) is the key.

[Roberto Perillo]

I synchronized all methods in my implementation of the Data class and got 80/80 for locking...

[Volker Abel]

Roberto, that's what I was looking for.

Thanks!