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Java > Open Source Codes > DEOS > Scheduler


1 //
2 // Copyright (C) 2005 United States Government as represented by the
3 // Administrator of the National Aeronautics and Space Administration
4 // (NASA). All Rights Reserved.
5 //
6 // This software is distributed under the NASA Open Source Agreement
7 // (NOSA), version 1.3. The NOSA has been approved by the Open Source
8 // Initiative. See the file NOSA-1.3-JPF at the top of the distribution
9 // directory tree for the complete NOSA document.
10 //
11 // THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
12 // KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
13 // LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
14 // SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
15 // A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT
16 // THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
17 // DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
18 //
19 package DEOS;
20
21 import gov.nasa.jpf.jvm.Verify;
22
23
24 /**
25  * DOCUMENT ME!
26  */
27 class Scheduler {
28   static Thread JavaDoc itsRunningThread;
29   static Thread JavaDoc itsIdleThread;
30   static PriorityListOfThreads itsRunnableList;
31
32   //static int systemTickCount = 0xFFFFFFFF ;
33 static DEOSProcess theProcess;
34   static SynchObject synch;
35
36   public static DEOSProcess currentProcess () {
37     return theProcess;
38   }
39
40   public static Thread JavaDoc currentThread () {
41     return itsRunningThread;
42   }
43
44   public static Thread JavaDoc idleThread () {
45     return itsIdleThread;
46   }
47
48   public static void initialize () {
49     // JAVA DEOS
50 synch = new SynchObject();
51
52
53     //System.out.println("Scheduler.initialize");
54 itsRunnableList = new PriorityListOfThreads();
55     initializeIdleProcess();
56
57     int interruptState = CPU.enterCritical();
58     itsRunningThread = itsIdleThread;
59     itsRunningThread.startChargingCPUTime();
60     CPU.exitCritical(interruptState);
61     theProcess = new DEOSProcess();
62     DEOSKernel.localStartThread(theProcess.mainThread(),
63                                 Registry.uSecsInFastestPeriod, 0);
64   }
65
66   public static int priorityForPeriodIndex (int thePeriodIndex) {
67     return Registry.numPeriods - thePeriodIndex;
68   }
69
70   public static PriorityListOfThreads runnableList () {
71     return itsRunnableList;
72   }
73
74   public static void scheduleAnyThread () {
75     //System.out.println("Scheduler.scheduleAnyThread: current = " +
76 // itsRunningThread);
77 if (!itsRunnableList.isEmpty()) {
78       if (itsRunningThread.currentPriority() < itsRunnableList.head().parent()
79                                                               .currentPriority()) {
80         //System.out.println("Preemption");
81 itsRunnableList.addAtBeginning(itsRunningThread.preemptionNode);
82         Scheduler.scheduleOtherThread();
83       } else {
84         //System.out.println("Running has Higher Priority, i.e. no Preemption");
85 itsRunningThread.stopChargingCPUTime(0);
86         itsRunningThread.startChargingCPUTime();
87       }
88     } else {
89       System.out.println("How can this be!!!");
90     }
91   }
92
93   public static void scheduleOtherThread () {
94     Thread JavaDoc newThread;
95     Thread JavaDoc fromThread = itsRunningThread;
96
97     // Verify.beginAtomic();
98 //System.out.println("Scheduler.scheduleOtherThread");
99 threadListNode runnableThreadListNode = itsRunnableList.head();
100     Thread JavaDoc runnableThread = runnableThreadListNode.parent();
101     newThread = runnableThread;
102     runnableThreadListNode.removeFromList();
103
104
105     // Verify.endAtomic();
106 fromThread.stopChargingCPUTime(0);
107
108
109     //Verify.endAtomic();
110 newThread.startChargingCPUTime(); // cannot add this to atomic, since
111
112
113     // it can block
114 // JAVA DEOS - All the threads wait on the synch object. To wake up
115 // the newThread we interrupt() it. Since it was waiting on the
116 // synch object and the fromThread has the lock on the synch object,
117 // the new thread won't run until we call wait(). This is intended
118 // to only allow on thread to be running at a time like in the real
119 // DEOS. - penix
120 itsRunningThread = newThread;
121
122     //System.out.println(fromThread + " waking up " + newThread);
123 // check to make sure the current thread is not also the new
124 // thread or no one will get interrupted...
125 //if (fromThread != newThread) {
126 // newThread.javaThread().interrupt();
127 // try{synch.wait();}
128 // catch(InterruptedException ex) {
129 // //System.out.println("Waking up again");
130 // };
131 //}
132 }
133
134   //private
135 static void handleSystemTickInterrupt () {
136     //System.out.println("Scheduler.handleSystemTickInterrupt");
137 StartOfPeriodEvent.eventForPeriodIndex(0).pulseEvent(0);
138     Scheduler.scheduleAnyThread();
139
140     // System.out.println("Scheduler.handleSystemTickInterrupt RETURN");
141 }
142
143   //private
144 static void handleTimerInterrupt () {
145     //System.out.println("Scheduler.handleTimerInterrupt");
146 itsRunningThread.cpuAllowanceExceeded();
147   }
148
149   private static void idleThreadMain () {
150     while (true) {
151     }
152   }
153
154   private static void initializeIdleProcess () {
155     //System.out.println("Scheduler.initializeIdleProcess");
156 itsIdleThread = new Thread JavaDoc("idle");
157
158
159     // %%%%%5 added this code to make it work see sched.spin file
160 itsIdleThread.ConceptualObjectConstructor(0);
161     itsIdleThread.setCurrentPriority(0);
162     itsIdleThread.waitForNextTriggeringEvent();
163
164     itsIdleThread.startOfPeriodWaitNode.removeFromList();
165
166
167     //SPIN Registry::periodDurationInMicroSecs(itsIdleThread->periodIndex())
168 itsIdleThread.setCPUBudget(Registry.periodDurationInMicroSecs(
169                                      itsIdleThread.periodIndex()));
170     itsIdleThread.budget().replenish();
171   }
172 }
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