com.cosylab.acs.maci.manager

Class ReaderPreferenceReadWriteLock

java.lang.Object

com.cosylab.acs.maci.manager.ReaderPreferenceReadWriteLock

public class ReaderPreferenceReadWriteLock
extends java.lang.Object

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

Nested Classes

Modifier and Type	Class and Description
protected class	ReaderPreferenceReadWriteLock.ReaderLock
protected class	ReaderPreferenceReadWriteLock.Signaller Reader and Writer requests are maintained in two different wait sets, by two different objects.
static interface	ReaderPreferenceReadWriteLock.Sync Main interface for locks, gates, and conditions.
protected class	ReaderPreferenceReadWriteLock.WriterLock

Field Summary

Fields

Modifier and Type	Field and Description
protected long	activeReaders_
protected java.lang.Thread	activeWriter_
protected ReaderPreferenceReadWriteLock.ReaderLock	readerLock_
protected long	waitingReaders_
protected long	waitingWriters_
protected ReaderPreferenceReadWriteLock.WriterLock	writerLock_

Constructor Summary

Constructors

Constructor and Description
ReaderPreferenceReadWriteLock()

Method Summary

Modifier and Type	Method and Description
protected boolean	allowReader()
protected void	cancelledWaitingReader()
protected void	cancelledWaitingWriter()
protected ReaderPreferenceReadWriteLock.Signaller	endRead() Called upon termination of a read.
protected ReaderPreferenceReadWriteLock.Signaller	endWrite() Called upon termination of a write.
ReaderPreferenceReadWriteLock.Sync	readLock()
protected boolean	startRead()
protected boolean	startReadFromNewReader()
protected boolean	startReadFromWaitingReader()
protected boolean	startWrite()
protected boolean	startWriteFromNewWriter()
protected boolean	startWriteFromWaitingWriter()
ReaderPreferenceReadWriteLock.Sync	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 ReaderPreferenceReadWriteLock.ReaderLock readerLock_

writerLock_

protected final ReaderPreferenceReadWriteLock.WriterLock writerLock_

Constructor Detail

ReaderPreferenceReadWriteLock

public ReaderPreferenceReadWriteLock()

Method Detail

writeLock

public ReaderPreferenceReadWriteLock.Sync writeLock()

readLock

public ReaderPreferenceReadWriteLock.Sync readLock()

cancelledWaitingReader

protected void cancelledWaitingReader()

cancelledWaitingWriter

protected void cancelledWaitingWriter()

allowReader

protected boolean allowReader()

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 ReaderPreferenceReadWriteLock.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 ReaderPreferenceReadWriteLock.Signaller endWrite()

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