edu.cmu.emulator.util
Class RWLock

java.lang.Object
  edu.cmu.emulator.util.RWLock

public final class RWLock
extends Object

A reader/writer lock. This lock will allow multiple readers, but only a single writer. TO DO: - prevent starvation of writers (will only happen under severe circumstances, but it should be made impossible)

Author:

Glenn Judd

Field Summary

private ArrayList	readers
private int	writeLockDepth
private Thread	writer

Constructor Summary

RWLock()

Method Summary

void	readLock() Obtain a read lock.
void	release() Release the lock.
void	verifyReadLock() Verifies that the current thread holds a read lock.
void	verifyWriteLock() Verifies that the current thread holds a write lock.
void	writeLock() Obtain an exclusive write lock.

Methods inherited from class java.lang.Object

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

Field Detail

readers

private ArrayList readers

writer

private Thread writer

writeLockDepth

private int writeLockDepth

Constructor Detail

RWLock

public RWLock()

Method Detail

readLock

public final void readLock()

Obtain a read lock. If a thread holding the write lock calls this method it will simply return still holding the write lock. That is write lock is also implicitly a read lock, and this method will not downgrade the write lock to a read lock without an explicit release.

writeLock

public final void writeLock()

Obtain an exclusive write lock. This method will wait for all readers to complete before obtaining a write lock. This method will not upgrade read locks to write locks.

release

public final void release()

Release the lock. This class tracks what sort of lock this thread holds, and will relase the appropriate lock.

verifyReadLock

public final void verifyReadLock()

Verifies that the current thread holds a read lock.

verifyWriteLock

public final void verifyWriteLock()

Verifies that the current thread holds a write lock.