Mutex.ReleaseMutex Metod

public:
 void ReleaseMutex();

public void ReleaseMutex();

member this.ReleaseMutex : unit -> unit

Public Sub ReleaseMutex ()

Undantag

Exempel

I följande exempel visas hur ett lokalt Mutex objekt används för att synkronisera åtkomst till en skyddad resurs. Tråden som skapar mutex äger den inte från början. Metoden ReleaseMutex används för att frigöra mutex när den inte längre behövs.

// This example shows how a Mutex is used to synchronize access
// to a protected resource. Unlike Monitor, Mutex can be used with
// WaitHandle.WaitAll and WaitAny, and can be passed across
// AppDomain boundaries.
 
using System;
using System.Threading;

class Test13
{
    // Create a new Mutex. The creating thread does not own the
    // Mutex.
    private static Mutex mut = new Mutex();
    private const int numIterations = 1;
    private const int numThreads = 3;

    static void Main()
    {
        // Create the threads that will use the protected resource.
        for(int i = 0; i < numThreads; i++)
        {
            Thread myThread = new Thread(new ThreadStart(MyThreadProc));
            myThread.Name = String.Format("Thread{0}", i + 1);
            myThread.Start();
        }

        // The main thread exits, but the application continues to
        // run until all foreground threads have exited.
    }

    private static void MyThreadProc()
    {
        for(int i = 0; i < numIterations; i++)
        {
            UseResource();
        }
    }

    // This method represents a resource that must be synchronized
    // so that only one thread at a time can enter.
    private static void UseResource()
    {
        // Wait until it is safe to enter.
        mut.WaitOne();

        Console.WriteLine("{0} has entered the protected area", 
            Thread.CurrentThread.Name);

        // Place code to access non-reentrant resources here.

        // Simulate some work.
        Thread.Sleep(500);

        Console.WriteLine("{0} is leaving the protected area\r\n", 
            Thread.CurrentThread.Name);
         
        // Release the Mutex.
        mut.ReleaseMutex();
    }
}

' This example shows how a Mutex is used to synchronize access
' to a protected resource. Unlike Monitor, Mutex can be used with
' WaitHandle.WaitAll and WaitAny, and can be passed across
' AppDomain boundaries.
 
Imports System.Threading

Class Test
    ' Create a new Mutex. The creating thread does not own the
    ' Mutex.
    Private Shared mut As New Mutex()
    Private Const numIterations As Integer = 1
    Private Const numThreads As Integer = 3

    <MTAThread> _
    Shared Sub Main()
        ' Create the threads that will use the protected resource.
        Dim i As Integer
        For i = 1 To numThreads
            Dim myThread As New Thread(AddressOf MyThreadProc)
            myThread.Name = [String].Format("Thread{0}", i)
            myThread.Start()
        Next i

        ' The main thread exits, but the application continues to
        ' run until all foreground threads have exited.

    End Sub

    Private Shared Sub MyThreadProc()
        Dim i As Integer
        For i = 1 To numIterations
            UseResource()
        Next i
    End Sub

    ' This method represents a resource that must be synchronized
    ' so that only one thread at a time can enter.
    Private Shared Sub UseResource()
        ' Wait until it is safe to enter.
        mut.WaitOne()

        Console.WriteLine("{0} has entered protected area", _
            Thread.CurrentThread.Name)

        ' Place code to access non-reentrant resources here.

        ' Simulate some work
        Thread.Sleep(500)

        Console.WriteLine("{0} is leaving protected area" & vbCrLf, _
            Thread.CurrentThread.Name)

        ' Release Mutex.
        mut.ReleaseMutex()
    End Sub
End Class

Kommentarer

När en tråd hämtar en mutex (till exempel genom att anropa dess WaitOne metod) måste den därefter anropa ReleaseMutex för att avstå från ägarskapet för mutex och avblockera andra trådar som försöker få ägarskap för mutex. Om försöket att få ägarskap för mutex misslyckas (till exempel när ett anrop till WaitOne metoden med en millisecondsTimeout eller en timeout parameter returneras false eftersom tidsgränsen för begäran överskrids) bör tråden inte heller anropa ReleaseMutex. I det här fallet bör tråden inte heller tillåtas att komma åt resursen som skyddas av mutex, vilket visas i följande exempel.

using System;
using System.Threading;

class Example
{
    // Create a new Mutex. The creating thread does not own the mutex.
    private static Mutex mut = new Mutex();
    private const int numIterations = 1;
    private const int numThreads = 3;

    static void Main()
    {
        Example ex = new Example();
        ex.StartThreads();
    }

     private void StartThreads()
     {
        // Create the threads that will use the protected resource.
        for(int i = 0; i < numThreads; i++)
        {
            Thread newThread = new Thread(new ThreadStart(ThreadProc));
            newThread.Name = String.Format("Thread{0}", i + 1);
            newThread.Start();
        }

        // The main thread returns to Main and exits, but the application continues to
        // run until all foreground threads have exited.
    }

    private static void ThreadProc()
    {
        for(int i = 0; i < numIterations; i++)
        {
            UseResource();
        }
    }

    // This method represents a resource that must be synchronized
    // so that only one thread at a time can enter.
    private static void UseResource()
    {
        // Wait until it is safe to enter, and do not enter if the request times out.
        Console.WriteLine("{0} is requesting the mutex", Thread.CurrentThread.Name);
        if (mut.WaitOne(1000)) {
           Console.WriteLine("{0} has entered the protected area", 
               Thread.CurrentThread.Name);
   
           // Place code to access non-reentrant resources here.
   
           // Simulate some work.
           Thread.Sleep(5000);
   
           Console.WriteLine("{0} is leaving the protected area", 
               Thread.CurrentThread.Name);
   
           // Release the Mutex.
              mut.ReleaseMutex();
           Console.WriteLine("{0} has released the mutex", 
                             Thread.CurrentThread.Name);
        }
        else {
           Console.WriteLine("{0} will not acquire the mutex", 
                             Thread.CurrentThread.Name);
        }
    }

    ~Example()
    {
       mut.Dispose();
    }
}
// The example displays output like the following:
//       Thread1 is requesting the mutex
//       Thread1 has entered the protected area
//       Thread2 is requesting the mutex
//       Thread3 is requesting the mutex
//       Thread2 will not acquire the mutex
//       Thread3 will not acquire the mutex
//       Thread1 is leaving the protected area
//       Thread1 has released the mutex

Imports System.Threading

Class Example
   ' Create a new Mutex. The creating thread does not own the mutex.
   Private mut As New Mutex()
   Private Const numIterations As Integer = 1
   Private Const numThreads As Integer = 3

   Public Shared Sub Main()
      Dim ex As New Example()
      ex.StartThreads()
   End Sub
   
   Private Sub StartThreads()
        ' Create the threads that will use the protected resource.
        For i As Integer = 0 To numThreads - 1
            Dim newThread As New Thread(AddressOf ThreadProc)
            newThread.Name = String.Format("Thread{0}", i + 1)
            newThread.Start()
        Next

        ' The main thread returns to Main and exits, but the application continues to
        ' run until all foreground threads have exited.
   End Sub

   Private Sub ThreadProc()
        For i As Integer = 0 To numIterations - 1
            UseResource()
        Next
   End Sub

   ' This method represents a resource that must be synchronized
   ' so that only one thread at a time can enter.
   Private Sub UseResource()
        ' Wait until it is safe to enter.
        Console.WriteLine("{0} is requesting the mutex", 
                          Thread.CurrentThread.Name)
        If mut.WaitOne(1000) Then
           Console.WriteLine("{0} has entered the protected area", 
               Thread.CurrentThread.Name)
   
           ' Place code to access non-reentrant resources here.
   
           ' Simulate some work.
           Thread.Sleep(5000)
   
           Console.WriteLine("{0} is leaving the protected area", 
               Thread.CurrentThread.Name)
   
           ' Release the Mutex.
           mut.ReleaseMutex()
           Console.WriteLine("{0} has released the mutex", 
                             Thread.CurrentThread.Name)
        Else
           Console.WriteLine("{0} will not acquire the mutex", 
                             Thread.CurrentThread.Name)
        End If
   End Sub
   
   Protected Overrides Sub Finalize()
      mut.Dispose()
   End Sub
End Class
' The example displays output like the following:
'       Thread1 is requesting the mutex
'       Thread1 has entered the protected area
'       Thread2 is requesting the mutex
'       Thread3 is requesting the mutex
'       Thread2 will not acquire the mutex
'       Thread3 will not acquire the mutex
'       Thread1 is leaving the protected area
'       Thread1 has released the mutex

En tråd som äger en mutex kan ange samma mutex i upprepade väntefunktionsanrop utan att blockera dess körning. Antalet anrop behålls av den vanliga språkkörningen. Tråden måste anropa ReleaseMutex samma antal gånger för att frigöra ägarskapet för mutex.

Om en tråd avslutas när den äger en mutex, sägs mutexen vara övergiven. Mutex-tillståndet är inställt på signalerat och nästa väntande tråd får ägarskap. Om ingen äger mutexen signaleras mutex-tillståndet. Från och med version 2.0 av .NET Framework genereras en AbandonedMutexException i nästa tråd som hämtar mutex. Före version 2.0 av .NET Framework utlöstes inget undantag.

När det gäller en systemomfattande mutex kan en övergiven mutex indikera att ett program plötsligt har avslutats (till exempel med hjälp av Windows Task Manager).

Se även

• hanterad trådning
• mutexes