org.objectweb.perseus.concurrency.pessimistic
Class RWPri2RLock

java.lang.Object
  org.objectweb.perseus.concurrency.pessimistic.Lock
      org.objectweb.perseus.concurrency.pessimistic.RWPri2RLock

public final class RWPri2RLock

extends Lock

A lock associated to an oid (see the "locks" map within the pessimistic concurrency manager). Provides "one writer/multiple readers" concurrency policy with priority to readers (there is a risk for starvation wrt writers).

Author:

E. Bruneton, P. Dechamboux

Field Summary

protected java.util.Set	readers The contexts that have a read lock for the oid to which this object is associated.
protected java.lang.Object	writer The contexts that have a lock for the oid to which this object is associated.

Fields inherited from class org.objectweb.perseus.concurrency.pessimistic.Lock

dg, hints, logger, oid, reservations

Constructor Summary

RWPri2RLock()

RWPri2RLock(java.lang.Object hints, DependencyGraph dg)

Method Summary

boolean	close(java.lang.Object ctxt) Removes the given context from the reader and writer lists of this lock.
byte	getMax()
void	readIntention(java.lang.Object ctxt) Acquires this lock in read mode for the given context.
void	writeIntention(java.lang.Object ctxt) Acquires this lock in write mode for the given context.

Methods inherited from class org.objectweb.perseus.concurrency.pessimistic.Lock

reserve

Methods inherited from class java.lang.Object

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

Field Detail

writer

protected java.lang.Object writer

The contexts that have a lock for the oid to which this object is associated.

readers

protected java.util.Set readers

The contexts that have a read lock for the oid to which this object is associated.

Constructor Detail

RWPri2RLock

public RWPri2RLock()

RWPri2RLock

public RWPri2RLock(java.lang.Object hints,
                   DependencyGraph dg)

Method Detail

readIntention

public void readIntention(java.lang.Object ctxt)
                   throws ConcurrencyException

Acquires this lock in read mode for the given context. This method blocks until the lock can be acquired in read mode by this context.

Specified by:

readIntention in class Lock

Parameters:

ctxt - a context.

Throws:

ConcurrencyException

writeIntention

public void writeIntention(java.lang.Object ctxt)
                    throws ConcurrencyException

Acquires this lock in write mode for the given context. This method blocks until the lock can be acquired in write mode by this context.

Specified by:

writeIntention in class Lock

Parameters:

ctxt - a context.

Throws:

ConcurrencyException

close

public boolean close(java.lang.Object ctxt)

Removes the given context from the reader and writer lists of this lock.

Specified by:

close in class Lock

Parameters:

ctxt - a context

Returns:

true if the reader and writer list are empty, after the context has been removed from these lists. In such a case, this object can be removed from the 'locks' map.

getMax

public byte getMax()

Specified by:

getMax in class Lock