org.objectweb.perseus.concurrency.distributed.globallock.api
Interface GlobalLock

All Known Implementing Classes:

GlobalLockUser

public interface GlobalLock

This is the interface of global locks. Global locks are created and associated w/ resource identifiers using the getGlobalLock of the GlobalLockManager interface. Once created the lock can be upgraded/downgraded to a specified level. The initial value is implementation dependent.

See Also:

GlobalLockManager

Method Summary

void	downgrade(byte lck) Notifies a lock downgrade.
byte	getGrantable() Get the maximum lock level that can be granted immediately without contacting the global lock coordinator (and so without blocking).
void	uncache() Uncache the lock level.
GlobalLockWaiter	upgrade(byte lck, boolean sync, long timeout) Request a lock upgrade.

Method Detail

upgrade

public GlobalLockWaiter upgrade(byte lck,
                                boolean sync,
                                long timeout)
                         throws DeadLockException,
                                java.lang.InterruptedException

Request a lock upgrade. In synchronous mode the method returns when the lock has been granted. In asynchronous mode the method returns a waiter object if the request cannot be granted immediately. The caller must call the waitLock method of this object to effectively wait for the lock. It must also call the signalHandled method when the granting has been handled to let other waiters be unblocked. This scheme let the possibility to implement a FIFO handling of requests.

Parameters:

lck - the requested lock level

sync - if true the method blocks until the request is granted

timeout - specifies the the maximum time to wait in sync mode

Returns:

a waiter object in asynchronous mode (sync == false) if the request cannot be satisfied immediately.

Throws:

DeadLockException - if the timeout has expired

java.lang.InterruptedException - if the thread has been interrupted while waiting

See Also:

GlobalLockWaiter

downgrade

public void downgrade(byte lck)

Notifies a lock downgrade.

Parameters:

lck - the new level wanted for the lock

getGrantable

public byte getGrantable()

Get the maximum lock level that can be granted immediately without contacting the global lock coordinator (and so without blocking). Note that this is just a hint. There is no guarantee that a subsequent call to upgrade will not block.

Returns:

the maximum grantable lock level

uncache

public void uncache()

Uncache the lock level. The following call to upgrade will automatically generate a request to the coordinator.