Csharp/CSharp Tutorial/Thread/Thread DeadLock

A sure-fire deadlock

<source lang="csharp">using System; using System.Collections.Generic; using System.Diagnostics; using System.IO; using System.Reflection; using System.Runtime; using System.Runtime.rupilerServices; using System.Security; using System.Text; using System.Threading; public class MainClass {

   private static object deadlockA = new object();
   private static object deadlockB = new object();
   
   public static void Main()
   {
       lock (deadlockA) {
           ThreadPool.QueueUserWorkItem(delegate {
               lock (deadlockB) {
                   Console.WriteLine("A");
                   lock (deadlockA) {
                       Console.WriteLine("B");
                   }
               }
           });
           lock (deadlockB) {
               Console.WriteLine("Main: got b");
           }
       }
   }

}</source>

Main: got b
A
B

Dining Philosopher

<source lang="csharp">/* Quote from C# and the .NET Framework by Bob Powell

• /

using System; using System.Threading; public struct PhilosopherData {

 public int        PhilosopherId;
 public Mutex      RightChopStick;
 public Mutex      LeftChopStick;
 public int        AmountToEat;
 public int        TotalFood;

}

public class Philosopher : WorkerThread {

 public Philosopher( object data ) : base( data ) { }
 protected override void Run( ) {
   PhilosopherData pd = (PhilosopherData)Data;
   Random r = new Random( pd.PhilosopherId );
   Console.WriteLine("Philosopher {0} ready", pd.PhilosopherId );
   WaitHandle[] chopSticks =  new WaitHandle[] { pd.LeftChopStick, pd.RightChopStick };
   while( pd.TotalFood > 0 ) {
     //Get both chop sticks
     WaitHandle.WaitAll( chopSticks );
     Console.WriteLine("Philosopher {0} eating {1} of {2} food", pd.PhilosopherId, pd.AmountToEat, pd.TotalFood );
     pd.TotalFood -= pd.AmountToEat;
     Thread.Sleep( r.Next(1000,5000) );
     
     //Release the chopsticks
     Console.WriteLine("Philosopher {0} thinking", pd.PhilosopherId);
     pd.RightChopStick.ReleaseMutex( );
     pd.LeftChopStick.ReleaseMutex( );
     //Think for a random time length
     Thread.Sleep( r.Next(1000,5000) );
   }
   Console.WriteLine("Philosopher {0} finished", pd.PhilosopherId );
 }

}

public class Restaurant {

 public static void Main( ) {
   Mutex[] chopSticks = new Mutex[5];
   //init the chopSticks
   for( int i = 0; i < 5; i++ )
     chopSticks[i] = new Mutex( false );
   
   //Create the Five Philosophers
   for( int i = 0; i < 5; i++ ) {
     PhilosopherData pd;
     pd.PhilosopherId = i + 1;
     pd.RightChopStick = chopSticks[ i - 1 >= 0 ? ( i - 1 ) : 4 ];
     pd.LeftChopStick = chopSticks[i];
     pd.AmountToEat = 5;
     pd.TotalFood = 35;
     Philosopher p = new Philosopher( pd );
     p.Start( );
   }
   Console.ReadLine( );
 }

} public abstract class WorkerThread {

 private object  ThreadData;
 private Thread  thisThread;

 //Properties
 public object Data {
   get { return ThreadData; }
   set { ThreadData = value; }
 }
 public object IsAlive {
   get { return thisThread == null ? false : thisThread.IsAlive; }
 }
 /// <summary>
 /// Constructors
 /// </summary>
 public WorkerThread( object data ) {
   this.ThreadData = data;
 }
 public WorkerThread( ) {
   ThreadData = null;
 }
 /// <summary>
 /// Public Methods
 /// </summary>
 
 /// <summary>
 /// Start the worker thread
 /// </summary>
 public void Start( ) {
   thisThread = new Thread( new ThreadStart( this.Run ) );
   thisThread.Start();
 }
 /// <summary>
 /// Stop the current thread.  Abort causes
 /// a ThreadAbortException to be raised within
 /// the thread
 /// </summary>
 public void Stop( ) {
   thisThread.Abort( );
   while( thisThread.IsAlive ) ;
   thisThread = null;
 }
 /// <summary>
 /// To be implemented by derived threads
 /// </summary>
 protected abstract void Run( );

}</source>

Philosopher 1 ready
Philosopher 1 eating 5 of 35 food
Philosopher 2 ready
Philosopher 3 ready
Philosopher 3 eating 5 of 35 food
Philosopher 4 ready
Philosopher 5 ready
Philosopher 1 thinking
Philosopher 5 eating 5 of 35 food
Philosopher 3 thinking
Philosopher 2 eating 5 of 35 food
Philosopher 5 thinking
Philosopher 4 eating 5 of 35 food
^CTerminate batch job (Y/N)? n