On Wed, 2004-01-07 at 10:08, Oliver Zeigermann wrote:
I had a lock a your GenericLocks, and I'd like to see TLocks replaced by your implementation. As far as I understand, GenericLocks with maxLevel=2 can emulate TLocks, so why not dump the special-case implementation?
Yes, maxLevel=2 could represent NO_LOCK, READ_LOCK and WRITE_LOCK.
You mentioned priorities ... does that mean, e.g. that threads waiting for read-locks should wake up before threads waiting before write-locks? That's not implemented in TLocks either, so that's not a reason to keep TLocks either.
Not quite sure... What I have seen, writers are preferred over readers when more than one thread is waiting to acquire a lock, correct? GenericLock does not support preferences like this.
What's your favorite book about all this? I need some background about isolation levels ... (I picked ReadWrite locks from Concurrent Programming in Java, Design principles and patterns, I like this book)
Apart from the web I have read the Doug Lea stuff only. I do not remember the title, but I think it is just the one you named...
Oliver
Michael
Michael Hartmeier wrote:
Aaaarghhh! Your code looks definitely better than mine ...
As I said my code in GenericLock was wrong as well! It does not seem to be that easy... I will take over the corrected for loop stated below...
Where did you checkin your GenericLock? We should change ParentStore to use your lock (or even better: use a common lock manager).
Well, as it seems we do not need this locking in the ParentStore any more. Still it might be a good idea to use the read/write lock idea from TLock. GenericLock is needed for the file store and does well without priorities. But - as it seems - caching will need non-blocking locks to support isolation levels higher than READ COMMITTED. read/write locks would be nice for this...
Locks are in org.apache.slide.util.locking{.impl}... When you have a look at it, have in mind GenericLock is a multi level lock, i.e. there is at most *one* multi level lock per resource, but the lock itself can have more than one lock level and more than one owner. This is a bit excentric, but I saw it fit just right...
Oliver
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