DonationGrader.java

package nachos.ag;

import nachos.machine.Machine;
import nachos.threads.KThread;
import nachos.threads.Lock;
import nachos.threads.PriorityScheduler;
import nachos.threads.ThreadedKernel;

/**
 * A grader for testing priority donation.
 * 
 * @author Xiangru Chen
 * 
 */
public class DonationGrader extends BasicTestGrader
{
  
  @Override
  public void run ()
  {
    assertTrue(ThreadedKernel.scheduler.getClass().getSimpleName().equals(
      "PriorityScheduler"), "This grader needs priority scheduler.");
    
    testLock();
    
    testJoin();
    
    done();
  }
  
  private void testLock ()
  {
    lock = new Lock();
    lock.acquire();
    
    boolean insStatus = Machine.interrupt().disable();
    ThreadedKernel.scheduler.setPriority(lowPriority);
    
    forkNewThread(new Runnable()
    {
      @Override
      public void run ()
      {
        lock.acquire();
        lock.release();
      }
    }, highPriority);
    
    forkNewThread(new Runnable()
    {
      @Override
      public void run ()
      {
        alwaysYield();
        assertTrue(false, "Maybe error in your priority donation.");
      }
    }, midPriority);
    
    Machine.interrupt().restore(insStatus);
    
    alwaysYield();
    lock.release();
  }
  
  private void testJoin ()
  {
    boolean insStatus = Machine.interrupt().disable();
    ThreadedKernel.scheduler.setPriority(highPriority);
    
    ThreadHandler low = forkNewThread(new Runnable()
    {
      @Override
      public void run ()
      {
        alwaysYield();
      }
    }, lowPriority);
    
    forkNewThread(new Runnable()
    {
      @Override
      public void run ()
      {
        alwaysYield();
        assertTrue(false, "Maybe error in your priority donation.");
      }
    }, midPriority);
    
    Machine.interrupt().restore(insStatus);
    low.thread.join();
  }
  
  private void alwaysYield ()
  {
    for (int i = 0; i < 10000; ++i)
    {
      KThread.yield();
    }
  }
  
  private Lock lock = null;
  
  public static final int highPriority = PriorityScheduler.priorityMaximum;
  public static final int midPriority = PriorityScheduler.priorityMaximum - 1;
  public static final int lowPriority = PriorityScheduler.priorityMaximum - 2;
  
}