aerodame

   case WAIT:
      // get the current thread id (use Scheduler.getMyTcb( ) )
      // let the current thread sleep in waitQueue under the condition
      // = this thread id (= tcb.getTid( ) )
	return OK; // return a child thread id who woke me up
   case EXIT:
      // get the current thread's parent id (= tcb.getPid( ) )
      // search waitQueue for and wakes up the thread under the condition
      // = the current thread's parent id
	return OK;

aerodame

   public static int interrupt( int irq, int cmd, int param, Object args ) {
	   TCB myTcb;
	   switch( irq ) {
	      case INTERRUPT_SOFTWARE: // System calls
            ...
            ...
	      case INTERRUPT_DISK: // Disk interrupts
	         // wake up the thread waiting for a service completion
	         ioQueue.dequeueAndWakeup( 2 );

aerodame

   Disk disk = new Disk( 1000 );
   SyncQueue ioQueue = new SyncQueue( );
   ...
   ...
   // a disk read operation:
   while ( disk.read( blockId, buffer ) == false ) {
      ioQueue.enqueueAndSleep( 1 ); // relinquish CPU to another ready thread
      // now check to ensure disk is not busy
      while ( disk.testAndResetReady( ) == false )
         ioQueue.enqueueAndSleep( 2 ); // relinquish CPU to another ready thread

aerodame

import java.util.*;
import java.lang.reflect.*;
import java.io.*;

public class Kernel {
    // Interrupt requests
    public final static int INTERRUPT_SOFTWARE = 1;  // System calls
    public final static int INTERRUPT_DISK     = 2;  // Disk interrupts
    public final static int INTERRUPT_IO       = 3;  // Other I/O interrupts

aerodame

   Disk disk = new Disk( 1000 );

   // a disk read operation:
   while ( disk.read( blockId, buffer ) == false )
      ; // busy wait
   while ( disk.testAndResetReady( ) == false )
      ; // another busy wait
   // now you can access data in buffer

aerodame

   // ----------------------- Start Debugger Method ---------------------------
   // Provide a simple debugger of the TCBs in queue
   // Format of output is = Q[]-> { [p,t] [p,t] [p,t] ... }
   // Where p = Process ID
   //       t = Thread ID
   // -------------------------------------------------------------------------
   private void dumpQueue(int time) {
      if (DEBUG) {
         System.out.print("\nT("+time+"): ");
         // how many TCBs are in queue

aerodame

public class PingPong extends Thread {
   private String word;
   private int loop;
   public PingPong( String[] args ) {
      word = args[0];
      loop = Integer.parseInt( args[1] );
   }
   public void run( ) {
      for ( int j = 0; j < 100; j++ ) {
         SysLib.cout( word + " " );

aerodame

public class PingPong extends Thread {
   private String word;
   private int loop;
   public PingPong( String[] args ) {
      word = args[0];
      loop = Integer.parseInt( args[1] );
   }
   public void run( ) {
      for ( int j = 0; j < 100; j++ ) {
         SysLib.cout( word + " " );

aerodame

public class ThreadDriver {
   public static void main( String[] args ) {
      String args[2];

      args[0] = "ping"; args[1] = "10000";
      new PingPong( args ).start( );

      args[0] = "PING"; args[1] = "90000";
      new PingPong( args ).start( );
   }

aerodame

   // Provide a quick debugger of the TCBs in queue
   // Format of output is = Q[i]-> { [p,t] [p,t] [p,t] ... } 
   private void dumpQueue(int time) {
      int N;
      if (DEBUG) {
         System.out.print("T("+time+"): ");
         // scan through each multilevel queue
         for (int i=0; i < 3; i++) {
            // how many TCBs are in queue
            N = queue[i].size();