org.exist.storage.lock
Class ReentrantReadWriteLock

java.lang.Object
  org.exist.storage.lock.ReentrantReadWriteLock

All Implemented Interfaces:

Lock

public class ReentrantReadWriteLock
extends Object
implements Lock

A lock with the same semantics as builtin Java synchronized locks: Once a thread has a lock, it can re-obtain it any number of times without blocking. The lock is made available to other threads when as many releases as acquires have occurred. The lock has a timeout: a read lock will be released if the timeout is reached.

Field Summary

int

mode_

Fields inherited from interface org.exist.storage.lock.Lock

NO_LOCK, READ_LOCK, WRITE_LOCK

Constructor Summary

ReentrantReadWriteLock(Object id)

Method Summary

boolean	acquire() Acquire a lock for read.
boolean	acquire(int mode) Acquire a lock for read or write.
boolean	attempt(int mode) Attempt to acquire a lock for read or write.
String	getId()
LockInfo	getLockInfo() Create a LockInfo entry for the given lock.
Thread	getOwner()
boolean	hasLock() Check if the lock is currently locked by someone.
boolean	hasLock(Thread owner) Check if the specified thread holds either a write or a read lock on the resource.
long	holds() Return the number of unreleased acquires performed by the current thread.
boolean	isLockedForRead(Thread owner) Check if the specified thread does currently hold a read lock.
boolean	isLockedForWrite() Returns true if there are active or pending write locks.
void	release(int mode) Release a lock of the specified type.
void	release(int mode, int count)
void	wakeUp() Wake up waiting threads and recompute dependencies.

Methods inherited from class java.lang.Object

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

Field Detail

mode_

public int mode_

Constructor Detail

ReentrantReadWriteLock

public ReentrantReadWriteLock(Object id)

Method Detail

getId

public String getId()

Specified by:

getId in interface Lock

acquire

public boolean acquire()
                throws LockException

Description copied from interface: Lock

Acquire a lock for read.

Specified by:

acquire in interface Lock

Throws:

LockException

acquire

public boolean acquire(int mode)
                throws LockException

Description copied from interface: Lock

Acquire a lock for read or write. mode is one of Lock.READ_LOCK or Lock.WRITE_LOCK.

Specified by:

acquire in interface Lock

Throws:

LockException

wakeUp

public void wakeUp()

Description copied from interface: Lock

Wake up waiting threads and recompute dependencies. Currently used to rerun deadlock detection.

Specified by:

wakeUp in interface Lock

attempt

public boolean attempt(int mode)

Description copied from interface: Lock

Attempt to acquire a lock for read or write. This method will fail immediately if the lock cannot be acquired.

Specified by:

attempt in interface Lock

isLockedForWrite

public boolean isLockedForWrite()

Description copied from interface: Lock

Returns true if there are active or pending write locks.

Specified by:

isLockedForWrite in interface Lock

isLockedForRead

public boolean isLockedForRead(Thread owner)

Description copied from interface: Lock

Check if the specified thread does currently hold a read lock.

Specified by:

isLockedForRead in interface Lock

Parameters:

owner - the thread to search for

Returns:

true if the thread holds a read lock

hasLock

public boolean hasLock()

Description copied from interface: Lock

Check if the lock is currently locked by someone.

Specified by:

hasLock in interface Lock

Returns:

true if there's an active read or write lock

hasLock

public boolean hasLock(Thread owner)

Description copied from interface: Lock

Check if the specified thread holds either a write or a read lock on the resource.

Specified by:

hasLock in interface Lock

Parameters:

owner - the thread

Returns:

true if owner has a lock

getOwner

public Thread getOwner()

release

public void release(int mode)

Description copied from interface: Lock

Release a lock of the specified type.

Specified by:

release in interface Lock

release

public void release(int mode,
                    int count)

Specified by:

release in interface Lock

holds

public long holds()

Return the number of unreleased acquires performed by the current thread. Returns zero if current thread does not hold lock.

getLockInfo

public LockInfo getLockInfo()

Description copied from interface: Lock

Create a LockInfo entry for the given lock.

Specified by:

getLockInfo in interface Lock

Returns:

the lock info