org.castor.util.concurrent

Class WriterPreferenceReadWriteLock

public class WriterPreferenceReadWriteLock extends Object implements ReadWriteLock

A ReadWriteLock that prefers waiting writers over waiting readers when there is contention. This class is adapted from the versions described in CPJ, improving on the ones there a bit by segregating reader and writer wait queues, which is typically more efficient.

The locks are NOT reentrant. In particular, even though it may appear to usually work OK, a thread holding a read lock should not attempt to re-acquire it. Doing so risks lockouts when there are also waiting writers.

[ Introduction to this package. ]

Nested Class Summary
protected class	WriterPreferenceReadWriteLock.ReaderLock
protected abstract class	WriterPreferenceReadWriteLock.Signaller Reader and Writer requests are maintained in two different wait sets, by two different objects.
protected class	WriterPreferenceReadWriteLock.WriterLock

Field Summary
protected long	activeReaders_
protected Thread	activeWriter_
protected WriterPreferenceReadWriteLock.ReaderLock	readerLock_
protected long	waitingReaders_
protected long	waitingWriters_
protected WriterPreferenceReadWriteLock.WriterLock	writerLock_

Method Summary
protected boolean	allowReader() Override this method to change to reader preference *
protected void	cancelledWaitingReader()
protected void	cancelledWaitingWriter()
protected WriterPreferenceReadWriteLock.Signaller	endRead() Called upon termination of a read.
protected WriterPreferenceReadWriteLock.Signaller	endWrite() Called upon termination of a write.
Sync	readLock()
protected boolean	startRead()
protected boolean	startReadFromNewReader()
protected boolean	startReadFromWaitingReader()
protected boolean	startWrite()
protected boolean	startWriteFromNewWriter()
protected boolean	startWriteFromWaitingWriter()
Sync	writeLock()