com.splicemachine.db.impl.services.locks

Class ConcurrentLockSet

java.lang.Object

com.splicemachine.db.impl.services.locks.ConcurrentLockSet

All Implemented Interfaces:

LockTable

final class ConcurrentLockSet
extends java.lang.Object
implements LockTable

A ConcurrentLockSet is a complete lock table which maps Lockables to LockControl objects.

A LockControl contains information about the locks held on a Lockable.
MT - Mutable : All public methods of this class, except addWaiters, are thread safe. addWaiters can only be called from the thread which performs deadlock detection. Only one thread can perform deadlock detection at a time.
The class creates ActiveLock and LockControl objects. LockControl objects are never passed out of this class, All the methods of LockControl are called while holding a ReentrantLock associated with the Lockable controlled by the LockControl, thus providing the single threading that LockControl required. Methods of Lockables are only called by this class or LockControl, and always while holding the corresponding ReentrantLock, thus providing the single threading that Lockable requires.

See Also:

LockControl

Constructor Summary

Constructors

Constructor and Description
ConcurrentLockSet(AbstractPool factory)

Method Summary

Modifier and Type	Method and Description
void	addWaiters(java.util.Map waiters) Add all waiters in this lock table to a Map object.
boolean	anyoneBlocked() Check whether anyone is blocked.
int	getWaitTimeout() Get the wait timeout in milliseconds.
Lock	lockObject(CompatibilitySpace compatibilitySpace, Lockable ref, java.lang.Object qualifier, int timeout) Lock an object within a specific compatibility space.
void	oneLessWaiter() Decrease blockCount by one.
void	oneMoreWaiter() Increase blockCount by one.
void	setDeadlockTimeout(int timeout) Set the deadlock timeout.
void	setDeadlockTrace(boolean val) Enable or disable tracing of deadlocks.
void	setWaitTimeout(int timeout) Set the wait timeout.
java.util.Map<Lockable,Control>	shallowClone() make a shallow clone of myself and my lock controls
void	unlock(Latch item, int unlockCount) Unlock an object, previously locked by lockObject().
Lock	unlockReference(CompatibilitySpace space, Lockable ref, java.lang.Object qualifier, java.util.Map group) Unlock an object once if it is present in the specified group.
boolean	zeroDurationLockObject(CompatibilitySpace space, Lockable ref, java.lang.Object qualifier, int timeout) Lock an object and release the lock immediately.

Methods inherited from class java.lang.Object

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

Constructor Detail

ConcurrentLockSet

ConcurrentLockSet(AbstractPool factory)

Method Detail

lockObject

public Lock lockObject(CompatibilitySpace compatibilitySpace,
                       Lockable ref,
                       java.lang.Object qualifier,
                       int timeout)
                throws StandardException

Lock an object within a specific compatibility space.

Specified by:

lockObject in interface LockTable

Parameters:

compatibilitySpace - Compatibility space.

ref - Lockable reference.

qualifier - Qualifier.

timeout - Timeout in milli-seconds

Returns:

Object that represents the lock.

Throws:

StandardException - Standard Derby policy.

unlock

public void unlock(Latch item,
                   int unlockCount)

Unlock an object, previously locked by lockObject(). If unlockCOunt is not zero then the lock will be unlocked that many times, otherwise the unlock count is taken from item.

Specified by:

unlock in interface LockTable

Parameters:

item - the lock to unlock

unlockCount - the number of times to unlock the item; or zero, meaning take the unlock count from the item

unlockReference

public Lock unlockReference(CompatibilitySpace space,
                            Lockable ref,
                            java.lang.Object qualifier,
                            java.util.Map group)

Unlock an object once if it is present in the specified group. Also remove the object from the group.

Specified by:

unlockReference in interface LockTable

Parameters:

space - the compatibility space

ref - a reference to the locked object

qualifier - qualifier of the lock

group - a map representing the locks in a group

Returns:

the corresponding lock in the group map, or null if the object was not unlocked

zeroDurationLockObject

public boolean zeroDurationLockObject(CompatibilitySpace space,
                                      Lockable ref,
                                      java.lang.Object qualifier,
                                      int timeout)
                               throws StandardException

Lock an object and release the lock immediately. Equivalent to

 Lock lock = lockTable.lockObject(space, ref, qualifier, timeout);
 lockTable.unlock(lock, 1);
 

except that the implementation might be more efficient.

Specified by:

zeroDurationLockObject in interface LockTable

Parameters:

space - the compatibility space

ref - a reference to the locked object

qualifier - qualifier of the lock

timeout - maximum time to wait in milliseconds (C_LockFactory.NO_WAIT means don't wait)

Returns:

true if the object was locked, or false if the object couldn't be locked immediately and timeout was NO_WAIT or LockOwner had the noWait flag set

Throws:

StandardException - if the lock could not be obtained

setDeadlockTimeout

public void setDeadlockTimeout(int timeout)

Set the deadlock timeout.

Specified by:

setDeadlockTimeout in interface LockTable

Parameters:

timeout - deadlock timeout in milliseconds

setWaitTimeout

public void setWaitTimeout(int timeout)

Set the wait timeout.

Specified by:

setWaitTimeout in interface LockTable

Parameters:

timeout - wait timeout in milliseconds

getWaitTimeout

public int getWaitTimeout()

Get the wait timeout in milliseconds.

Specified by:

getWaitTimeout in interface LockTable

setDeadlockTrace

public void setDeadlockTrace(boolean val)

Description copied from interface: LockTable

Enable or disable tracing of deadlocks.

Specified by:

setDeadlockTrace in interface LockTable

Parameters:

val - true enables tracing, false disables tracing

addWaiters

public void addWaiters(java.util.Map waiters)

Add all waiters in this lock table to a Map object. This method can only be called by the thread that is currently performing deadlock detection. All entries that are visited in the lock table will be locked when this method returns. The entries that have been seen and locked will be unlocked after the deadlock detection has finished.

Specified by:

addWaiters in interface LockTable

Parameters:

waiters - the map to add the waiters to

See Also:

LockControl.addWaiters(java.util.Map)

shallowClone

public java.util.Map<Lockable,Control> shallowClone()

make a shallow clone of myself and my lock controls

Specified by:

shallowClone in interface LockTable

Returns:

a shallow clone of the lock table

oneMoreWaiter

public void oneMoreWaiter()

Increase blockCount by one.

Specified by:

oneMoreWaiter in interface LockTable

oneLessWaiter

public void oneLessWaiter()

Decrease blockCount by one.

Specified by:

oneLessWaiter in interface LockTable

anyoneBlocked

public boolean anyoneBlocked()

Check whether anyone is blocked.

Specified by:

anyoneBlocked in interface LockTable

Returns:

true if someone is blocked, false otherwise