com.sleepycat.je.latch

Class SharedLatchImpl

java.lang.Object

com.sleepycat.je.latch.SharedLatchImpl

All Implemented Interfaces:

SharedLatch

public class SharedLatchImpl
extends java.lang.Object
implements SharedLatch

Simple thread-based non-transactional reader-writer/shared-exclusive latch. Latches provide simple exclusive or shared transient locks on objects. Latches are expected to be held for short, defined periods of time. No deadlock detection is provided so it is the caller's responsibility to sequence latch acquisition in an ordered fashion to avoid deadlocks. Nested latches for a single thread are supported, but upgrading a shared latch to an exclusive latch is not. This implementation is based on the section Reader-Writer Locks in the book Java Threads by Scott Oaks, 2nd Edition, Chapter 8. This SharedLatch implementation is only used when Java 5 ReentrantReadWriteLocks are not available.

Constructor Summary

Constructors

Constructor and Description
SharedLatchImpl(java.lang.String name, EnvironmentImpl env) Create a shared latch.

Method Summary

Methods

Modifier and Type	Method and Description
void	acquireExclusive() Acquire a latch for exclusive/write access.
boolean	acquireExclusiveNoWait() Probe a latch for exclusive access, but don't block if it's not available.
void	acquireShared() Acquire a latch for shared/read access.
boolean	isOwner() Return true if this thread is an owner, reader, or write.
boolean	isWriteLockedByCurrentThread()
void	release() Release an exclusive or shared latch.
void	releaseIfOwner() Release the latch.
void	setExclusiveOnly(boolean exclusiveOnly) Indicate whether this latch can only be set exclusively (not shared).
void	setName(java.lang.String name) Set the latch name, used for latches in objects instantiated from the log.
boolean	setNoteLatch(boolean noteLatch) If noteLatch is true, then track latch usage in the latchTable.

Methods inherited from class java.lang.Object

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

Constructor Detail

SharedLatchImpl

public SharedLatchImpl(java.lang.String name,
               EnvironmentImpl env)

Create a shared latch.

Method Detail

setExclusiveOnly

public void setExclusiveOnly(boolean exclusiveOnly)

Indicate whether this latch can only be set exclusively (not shared).

Specified by:

setExclusiveOnly in interface SharedLatch

setName

public void setName(java.lang.String name)

Set the latch name, used for latches in objects instantiated from the log.

Specified by:

setName in interface SharedLatch

setNoteLatch

public boolean setNoteLatch(boolean noteLatch)

If noteLatch is true, then track latch usage in the latchTable. Return true so this can be called under an assert.

Specified by:

setNoteLatch in interface SharedLatch

acquireExclusive

public void acquireExclusive()
                      throws DatabaseException

Acquire a latch for exclusive/write access. Nesting is not allowed, that is, the latch may not be acquired more than once by the same thread for exclusive access. Further, if the thread already holds the latch for shared access, it cannot be upgraded and LatchException will be thrown. Wait for the latch if some other thread is holding it. If there are threads waiting for access, they will be granted the latch on a FIFO basis. When the method returns, the latch is held for exclusive access.

Specified by:

acquireExclusive in interface SharedLatch

Throws:

LatchException - if the latch is already held by the current thread for shared access.

RunRecoveryException - if an InterruptedException exception occurs.

DatabaseException

acquireExclusiveNoWait

public boolean acquireExclusiveNoWait()
                               throws DatabaseException

Description copied from interface: SharedLatch

Probe a latch for exclusive access, but don't block if it's not available.

Specified by:

acquireExclusiveNoWait in interface SharedLatch

Returns:

true if the latch was acquired, false if it is not available.

Throws:

LatchException - if the latch is already held by the calling thread.

DatabaseException

acquireShared

public void acquireShared()
                   throws DatabaseException

Acquire a latch for shared/read access. Nesting is allowed, that is, the latch may be acquired more than once by the same thread.

Specified by:

acquireShared in interface SharedLatch

Throws:

RunRecoveryException - if an InterruptedException exception occurs.

DatabaseException

isOwner

public boolean isOwner()

Description copied from interface: SharedLatch

Return true if this thread is an owner, reader, or write.

Specified by:

isOwner in interface SharedLatch

release

public void release()
             throws LatchNotHeldException

Release an exclusive or shared latch. If there are other thread(s) waiting for the latch, they are woken up and granted the latch.

Specified by:

release in interface SharedLatch

Throws:

LatchNotHeldException

releaseIfOwner

public void releaseIfOwner()
                    throws LatchNotHeldException

Description copied from interface: SharedLatch

Release the latch. If there are other thread(s) waiting for the latch, one is woken up and granted the latch. If the latch was not owned by the caller, just return.

Specified by:

releaseIfOwner in interface SharedLatch

Throws:

LatchNotHeldException

isWriteLockedByCurrentThread

public boolean isWriteLockedByCurrentThread()

Specified by:

isWriteLockedByCurrentThread in interface SharedLatch