/*
*
* Copyright (c) 1997-1999 Scott Oaks and Henry Wong. All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software
* and its documentation for NON-COMMERCIAL purposes and
* without fee is hereby granted.
*
* This sample source code is provided for example only,
* on an unsupported, as-is basis.
*
* AUTHOR MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
* THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
* TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE, OR NON-INFRINGEMENT. AUTHOR SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
*
* THIS SOFTWARE IS NOT DESIGNED OR INTENDED FOR USE OR RESALE AS ON-LINE
* CONTROL EQUIPMENT IN HAZARDOUS ENVIRONMENTS REQUIRING FAIL-SAFE
* PERFORMANCE, SUCH AS IN THE OPERATION OF NUCLEAR FACILITIES, AIRCRAFT
* NAVIGATION OR COMMUNICATION SYSTEMS, AIR TRAFFIC CONTROL, DIRECT LIFE
* SUPPORT MACHINES, OR WEAPONS SYSTEMS, IN WHICH THE FAILURE OF THE
* SOFTWARE COULD LEAD DIRECTLY TO DEATH, PERSONAL INJURY, OR SEVERE
* PHYSICAL OR ENVIRONMENTAL DAMAGE ("HIGH RISK ACTIVITIES"). AUTHOR
* SPECIFICALLY DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR
* HIGH RISK ACTIVITIES.
*/
public class PriorityBusyFlag extends BusyFlag {
protected int currentPriority;
public synchronized void getBusyFlag() {
while (tryGetBusyFlag() == false) {
Thread prevOwner = getBusyFlagOwner();
try {
int curP = Thread.currentThread().getPriority();
if (curP > prevOwner.getPriority()) {
prevOwner.setPriority(curP);
}
wait();
} catch (Exception e) {}
}
}
public synchronized boolean tryGetBusyFlag() {
boolean succeed = super.tryGetBusyFlag();
if (succeed)
currentPriority = Thread.currentThread().getPriority();
return succeed;
}
public synchronized void freeBusyFlag() {
if (getBusyFlagOwner() == Thread.currentThread()) {
super.freeBusyFlag();
if (getBusyFlagOwner() == null) {
Thread.currentThread().setPriority(currentPriority);
notifyAll();
}
}
}
}
|