org.logicalcobwebs.concurrent
Class WriterPreferenceReadWriteLock

java.lang.Object
  org.logicalcobwebs.concurrent.WriterPreferenceReadWriteLock

All Implemented Interfaces:

ReadWriteLock

Direct Known Subclasses:

ReaderPreferenceReadWriteLock

public class WriterPreferenceReadWriteLock
extends java.lang.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 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 java.lang.Thread	activeWriter_
protected WriterPreferenceReadWriteLock.ReaderLock	readerLock_
protected long	waitingReaders_
protected long	waitingWriters_
protected WriterPreferenceReadWriteLock.WriterLock	writerLock_

Constructor Summary

WriterPreferenceReadWriteLock()

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() get the readLock
protected boolean	startRead()
protected boolean	startReadFromNewReader()
protected boolean	startReadFromWaitingReader()
protected boolean	startWrite()
protected boolean	startWriteFromNewWriter()
protected boolean	startWriteFromWaitingWriter()
Sync	writeLock() get the writeLock

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

activeReaders_

protected long activeReaders_

activeWriter_

protected java.lang.Thread activeWriter_

waitingReaders_

protected long waitingReaders_

waitingWriters_

protected long waitingWriters_

readerLock_

protected final WriterPreferenceReadWriteLock.ReaderLock readerLock_

writerLock_

protected final WriterPreferenceReadWriteLock.WriterLock writerLock_

Constructor Detail

WriterPreferenceReadWriteLock

public WriterPreferenceReadWriteLock()

Method Detail

writeLock

public Sync writeLock()

Description copied from interface: ReadWriteLock

get the writeLock

Specified by:

writeLock in interface ReadWriteLock

readLock

public Sync readLock()

Description copied from interface: ReadWriteLock

get the readLock

Specified by:

readLock in interface ReadWriteLock

cancelledWaitingReader

protected void cancelledWaitingReader()

cancelledWaitingWriter

protected void cancelledWaitingWriter()

allowReader

protected boolean allowReader()

Override this method to change to reader preference

startRead

protected boolean startRead()

startWrite

protected boolean startWrite()

startReadFromNewReader

protected boolean startReadFromNewReader()

startWriteFromNewWriter

protected boolean startWriteFromNewWriter()

startReadFromWaitingReader

protected boolean startReadFromWaitingReader()

startWriteFromWaitingWriter

protected boolean startWriteFromWaitingWriter()

endRead

protected WriterPreferenceReadWriteLock.Signaller endRead()

Called upon termination of a read. Returns the object to signal to wake up a waiter, or null if no such

endWrite

protected WriterPreferenceReadWriteLock.Signaller endWrite()

Called upon termination of a write. Returns the object to signal to wake up a waiter, or null if no such