Thread DeadLock: Philosopher : Thread DeadLock « Thread « VB.Net

1. VB.Net
2. Thread
3. Thread DeadLock

Thread DeadLock: Philosopher

Imports System
Imports System.Threading
Imports System.Text
Imports System.Windows.Forms

Public Class MainClass
  

  Public Shared Sub Main()
    Dim Tom As New Philosopher("Tom")
    Dim Bob As New Philosopher("Bob")
    Dim aThreadStart As New ThreadStart(AddressOf Tom.Eat)
    Dim aThread As New Thread(aThreadStart)
    aThread.Name = "Tom"
    
    Dim bThreadStart As New ThreadStart(AddressOf Bob.Eat)
    Dim bThread As New Thread(bThreadStart)
    bThread.Name = "Bob"
    aThread.Start()
    bThread.Start()
  End Sub
  

End Class



Public Class Fork
  Private Shared mForkAvailable As Boolean = True
  Private Shared OwnerName As String = "Nobody"

  Public Sub GrabFork(ByVal a As Philosopher)
    Console.WriteLine(Thread.CurrentThread.Name & " trying to grab the fork.")
    Console.WriteLine(Me.OwnerName & " has the fork.")
    Monitor.Enter(Me) 'SyncLock (aFork) '
    If mForkAvailable Then
      a.HasFork = True
      OwnerName = a.MyName
      mForkAvailable = False
      Console.WriteLine(a.MyName & " just got the fork, waiting")
      Thread.Sleep(100)
    End If
    Monitor.Exit(Me) 'End SyncLock
  End Sub
End Class

Public Class Knife
  Private Shared mKnifeAvailable As Boolean = True
  Private Shared OwnerName As String = "Nobody"

  Public Sub GrabKnife(ByVal a As Philosopher)
    Console.WriteLine(Thread.CurrentThread.Name & " trying to grab the knife.")
    Console.WriteLine(Me.OwnerName & " has the knife.")
    Monitor.Enter(Me) 'SyncLock (aKnife) '
    If mKnifeAvailable Then
      mKnifeAvailable = False
      a.HasKnife = True
      OwnerName = a.MyName
      Console.WriteLine(a.MyName & " just got the knife, waiting")
      Thread.Sleep(100)
    End If
    Monitor.Exit(Me)
  End Sub
End Class
Public Class Philosopher
  Public MyName As String
  Private Shared mFork As Fork
  Private Shared mKnife As Knife
  Public HasKnife As Boolean
  Public HasFork As Boolean

  Shared Sub New()
    mFork = New Fork()
    mKnife = New Knife()
  End Sub
  Public Sub New(ByVal theName As String)
    MyName = theName
  End Sub

  Public Sub Eat()
    Do Until Me.HasKnife And Me.HasFork
      Console.WriteLine(Thread.CurrentThread.Name & " is in the thread.")
      If Rnd() < 0.5 Then
        mFork.GrabFork(Me)
      Else
        mKnife.GrabKnife(Me)
      End If
    Loop
    MessageBox.Show(Me.MyName & " can eat!")
    mKnife = New Knife()
    mFork = New Fork()
  End Sub
End Class

           
       

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