Package org.infinispan.util.concurrent.locks

Class StripedLock

java.lang.Object

org.infinispan.util.concurrent.locks.StripedLock

@ThreadSafe
public class StripedLock
extends Object

A simple implementation of lock striping, using cache entry keys to lock on, primarily used to help make CacheLoader implemtations thread safe.

Backed by a set of ReentrantReadWriteLock instances, and using the key hashcodes to determine buckets.

Since buckets are used, it doesn't matter that the key in question is not removed from the lock map when no longer in use, since the key is not referenced in this class. Rather, the hash code is used.

Since:

4.0

Author:

Manik Surtani, Mircea.Markus@jboss.com

Constructor Summary

Constructors

Constructor	Description
StripedLock()	This constructor just calls StripedLock(int) with a default concurrency value of 20.
StripedLock(int concurrency)	Creates a new StripedLock which uses a certain number of shared locks across all elements that need to be locked.

Method Summary

Modifier and Type	Method	Description
void	acquireAllLocks(List<Object> keys, boolean exclusive)	Acquires locks on keys passed in.
boolean	acquireGlobalLock(boolean exclusive, long timeout)	Acquires RL on all locks aggregated by this StripedLock, in the given timeout.
void	acquireLock(Object key, boolean exclusive)	Blocks until a lock is acquired.
boolean	acquireLock(Object key, boolean exclusive, long millis)
void	downgradeLock(Object key)
int	getSharedLockCount()
int	getTotalLockCount()	Returns the total number of locks held by this class.
int	getTotalReadLockCount()
int	getTotalWriteLockCount()
void	releaseAllLocks(List<Object> keys)	Releases locks on all keys passed in.
void	releaseGlobalLock(boolean exclusive)
void	releaseLock(Object key)	Releases a lock the caller may be holding.
void	upgradeLock(Object key)

Methods inherited from class java.lang.Object

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

Constructor Detail

StripedLock

public StripedLock()

This constructor just calls StripedLock(int) with a default concurrency value of 20.

StripedLock

public StripedLock(int concurrency)

Creates a new StripedLock which uses a certain number of shared locks across all elements that need to be locked.

Parameters:

concurrency - number of threads expected to use this class concurrently.

Method Detail

acquireLock

public void acquireLock(Object key,
                        boolean exclusive)

Blocks until a lock is acquired.

Parameters:

exclusive - if true, a write (exclusive) lock is attempted, otherwise a read (shared) lock is used.

acquireLock

public boolean acquireLock(Object key,
                           boolean exclusive,
                           long millis)

releaseLock

public void releaseLock(Object key)

Releases a lock the caller may be holding. This method is idempotent.

upgradeLock

public void upgradeLock(Object key)

downgradeLock

public void downgradeLock(Object key)

releaseAllLocks

public void releaseAllLocks(List<Object> keys)

Releases locks on all keys passed in. Makes multiple calls to releaseLock(Object). This method is idempotent.

Parameters:

keys - keys to unlock

acquireAllLocks

public void acquireAllLocks(List<Object> keys,
                            boolean exclusive)

Acquires locks on keys passed in. Makes multiple calls to acquireLock(Object, boolean)

Parameters:

keys - keys to unlock

exclusive - whether locks are exclusive.

getTotalLockCount

public int getTotalLockCount()

Returns the total number of locks held by this class.

acquireGlobalLock

public boolean acquireGlobalLock(boolean exclusive,
                                 long timeout)

Acquires RL on all locks aggregated by this StripedLock, in the given timeout.

releaseGlobalLock

public void releaseGlobalLock(boolean exclusive)

getTotalReadLockCount

public int getTotalReadLockCount()

getSharedLockCount

public int getSharedLockCount()

getTotalWriteLockCount

public int getTotalWriteLockCount()