org.cache2k.core.concurrency

Class NonOptimisticLock

java.lang.Object

org.cache2k.core.concurrency.NonOptimisticLock

All Implemented Interfaces:

OptimisticLock

public class NonOptimisticLock
extends Object
implements OptimisticLock

Fallback locking mechanism when StampedLock is not available. This lock denies optimistic locking and uses a single write lock.

Optimistic locking is only possible on a Java 8 VM that support the loadFence instructions. Otherwise loads might get reordered after the validate, causing wrong results.

Author:

Jens Wilke

Constructor Summary

Constructors

Constructor and Description
NonOptimisticLock()

Method Summary

Modifier and Type	Method and Description
long	readLock() Non-exclusively acquires the lock, blocking if necessary until available.
long	tryOptimisticRead() This is a read access on the lock state for data visibility.
void	unlockRead(long stamp) If the lock state matches the given stamp, releases the non-exclusive lock.
void	unlockWrite(long stamp) If the lock state matches the given stamp, releases the exclusive lock.
boolean	validate(long stamp) Always false, optimistic locking not supported.
long	writeLock() Exclusively acquires the lock, blocking if necessary until available.

Methods inherited from class java.lang.Object

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

Constructor Detail

NonOptimisticLock

public NonOptimisticLock()

Method Detail

readLock

public long readLock()

Description copied from interface: OptimisticLock

Non-exclusively acquires the lock, blocking if necessary until available.

Specified by:

readLock in interface OptimisticLock

Returns:

a stamp that can be used to unlock or convert mode

writeLock

public long writeLock()

Description copied from interface: OptimisticLock

Exclusively acquires the lock, blocking if necessary until available.

Specified by:

writeLock in interface OptimisticLock

Returns:

a stamp that can be used to unlock or convert mode

tryOptimisticRead

public long tryOptimisticRead()

This is a read access on the lock state for data visibility. Normal stamped lock return 0 for exclusive lock.

Specified by:

tryOptimisticRead in interface OptimisticLock

Returns:

a stamp, or zero if exclusively locked

validate

public boolean validate(long stamp)

Always false, optimistic locking not supported.

Specified by:

validate in interface OptimisticLock

Parameters:

stamp - a stamp

Returns:

true if the lock has not been exclusively acquired since issuance of the given stamp; else false

unlockRead

public void unlockRead(long stamp)

Description copied from interface: OptimisticLock

If the lock state matches the given stamp, releases the non-exclusive lock.

Specified by:

unlockRead in interface OptimisticLock

Parameters:

stamp - a stamp returned by a read-lock operation

unlockWrite

public void unlockWrite(long stamp)

Description copied from interface: OptimisticLock

If the lock state matches the given stamp, releases the exclusive lock.

Specified by:

unlockWrite in interface OptimisticLock

Parameters:

stamp - a stamp returned by a write-lock operation