ReaderWriterLock.RestoreLock-Methode

Stellt den Sperrstatus des Threads mit dem Status vor dem Aufruf von ReleaseLock wieder her.

Namespace: System.Threading
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
Public Sub RestoreLock ( _
    ByRef lockCookie As LockCookie _
)
'Usage
Dim instance As ReaderWriterLock
Dim lockCookie As LockCookie

instance.RestoreLock(lockCookie)

public void RestoreLock (
    ref LockCookie lockCookie
)

public:
void RestoreLock (
    LockCookie% lockCookie
)

public void RestoreLock (
    /** @ref */ LockCookie lockCookie
)

JScript unterstützt die Übergabe von Werttypargumenten als Verweis nicht.

Parameter

• lockCookie
  Ein von ReleaseLock zurückgegebenes LockCookie.

Ausnahmen

Hinweise

Der von RestoreLock wiederhergestellte Zustand schließt die rekursive Sperrenanzahl ein.

Ein Thread wird blockiert, wenn eine Lesesperre wiederhergestellt werden soll, nachdem ein anderer Thread die Schreibsperre erhalten hat. Er wird ebenfalls blockiert, wenn die Schreibsperre wiederhergestellt werden soll, nachdem ein anderer Thread eine Lese- oder Schreibsperre erhalten hat. Da RestoreLock keine Timeouts akzeptiert, müssen Sie auf mögliche Deadlocks achten.

Verwenden Sie kein von UpgradeToWriterLock zurückgegebenes LockCookie.

Beispiel

' The complete code is located in the ReaderWriterLock
' class topic.
Imports System
Imports System.Threading
Imports Microsoft.VisualBasic

Public Class Test
    ' Declaring the ReaderWriterLock at the class level
    ' makes it visible to all threads.
    Private Shared rwl As New ReaderWriterLock()
    ' For this example, the shared resource protected by the
    ' ReaderWriterLock is just an integer.
    Private Shared resource As Integer = 0

...
    ' Shows how to release all locks and later restore
    ' the lock state. Shows how to use sequence numbers
    ' to determine whether another thread has obtained
    ' a writer lock since this thread last accessed the
    ' resource.
    Shared Sub ReleaseRestore(timeOut As Integer)
        Dim lastWriter As Integer
      
        Try
            rwl.AcquireReaderLock(timeOut)
            Try
                ' It is safe for this thread to read from
                ' the shared resource. Cache the value. (You
                ' might do this if reading the resource is
                ' an expensive operation.)
                Dim resourceValue As Integer = resource
                Display("reads resource value " & resourceValue)
                Interlocked.Increment(reads)
            
                ' Save the current writer sequence number.
                lastWriter = rwl.WriterSeqNum
            
                ' Release the lock, and save a cookie so the
                ' lock can be restored later.
                Dim lc As LockCookie = rwl.ReleaseLock()
            
                ' Wait for a random interval (up to a 
                ' quarter of a second), and then restore
                ' the previous state of the lock. Note that
                ' there is no time-out on the Restore method.
                Thread.Sleep(rnd.Next(250))
                rwl.RestoreLock(lc)
           
                ' Check whether other threads obtained the
                ' writer lock in the interval. If not, then
                ' the cached value of the resource is still
                ' valid.
                If rwl.AnyWritersSince(lastWriter) Then
                    resourceValue = resource
                    Interlocked.Increment(reads)
                    Display("resource has changed " & resourceValue)
                Else
                    Display("resource has not changed " & resourceValue)
                End If
            Finally
                ' Ensure that the lock is released.
                rwl.ReleaseReaderLock()
            End Try
        Catch ex As ApplicationException
            ' The reader lock request timed out.
            Interlocked.Increment(readerTimeouts)
        End Try
    End Sub 'ReleaseRestore

...
End Class 'Test 

// The complete code is located in the ReaderWriterLock
// class topic.
using System;
using System.Threading;

public class Test
{
    // Declaring the ReaderWriterLock at the class level
    // makes it visible to all threads.
    static ReaderWriterLock rwl = new ReaderWriterLock();
    // For this example, the shared resource protected by the
    // ReaderWriterLock is just an integer.
    static int resource = 0;

...
    // Shows how to release all locks and later restore
    // the lock state. Shows how to use sequence numbers
    // to determine whether another thread has obtained
    // a writer lock since this thread last accessed the
    // resource.
    static void ReleaseRestore(int timeOut)
    {
        int lastWriter;

        try
        {
            rwl.AcquireReaderLock(timeOut);
            try
            {
                // It is safe for this thread to read from
                // the shared resource. Cache the value. (You
                // might do this if reading the resource is
                // an expensive operation.)
                int resourceValue = resource;
                Display("reads resource value " + resourceValue); 
                Interlocked.Increment(ref reads);

                // Save the current writer sequence number.
                lastWriter = rwl.WriterSeqNum;

                // Release the lock, and save a cookie so the
                // lock can be restored later.
                LockCookie lc = rwl.ReleaseLock();

                // Wait for a random interval (up to a 
                // quarter of a second), and then restore
                // the previous state of the lock. Note that
                // there is no time-out on the Restore method.
                Thread.Sleep(rnd.Next(250));
                rwl.RestoreLock(ref lc);

                // Check whether other threads obtained the
                // writer lock in the interval. If not, then
                // the cached value of the resource is still
                // valid.
                if (rwl.AnyWritersSince(lastWriter))
                {
                    resourceValue = resource;
                    Interlocked.Increment(ref reads);
                    Display("resource has changed " + resourceValue);
                }
                else
                {
                    Display("resource has not changed " + resourceValue);
                }
            }        
            finally
            {
                // Ensure that the lock is released.
                rwl.ReleaseReaderLock();
            }
        }
        catch (ApplicationException)
        {
            // The reader lock request timed out.
            Interlocked.Increment(ref readerTimeouts);
        }
    }

...
}

// The complete code is located in the ReaderWriterLock
// class topic.
using namespace System;
using namespace System::Threading;
public ref class Test
{
public:

   // Declaring the ReaderWriterLock at the class level
   // makes it visible to all threads.
   static ReaderWriterLock^ rwl = gcnew ReaderWriterLock;

   // For this example, the shared resource protected by the
   // ReaderWriterLock is just an integer.
   static int resource = 0;


...
   // Shows how to release all locks and later restore
   // the lock state. Shows how to use sequence numbers
   // to determine whether another thread has obtained
   // a writer lock since this thread last accessed the
   // resource.
   static void ReleaseRestore( int timeOut )
   {
      int lastWriter;
      try
      {
         rwl->AcquireReaderLock( timeOut );
         try
         {
            
            // It is safe for this thread to read from
            // the shared resource. Cache the value. (You
            // might do this if reading the resource is
            // an expensive operation.)
            int resourceValue = resource;
            Display( String::Format( "reads resource value {0}", resourceValue ) );
            Interlocked::Increment( reads );
            
            // Save the current writer sequence number.
            lastWriter = rwl->WriterSeqNum;
            
            // Release the lock, and save a cookie so the
            // lock can be restored later.
            LockCookie lc = rwl->ReleaseLock();
            
            // Wait for a random interval (up to a 
            // quarter of a second), and then restore
            // the previous state of the lock. Note that
            // there is no timeout on the Restore method.
            Thread::Sleep( rnd->Next( 250 ) );
            rwl->RestoreLock( lc );
            
            // Check whether other threads obtained the
            // writer lock in the interval. If not, then
            // the cached value of the resource is still
            // valid.
            if ( rwl->AnyWritersSince( lastWriter ) )
            {
               resourceValue = resource;
               Interlocked::Increment( reads );
               Display( String::Format( "resource has changed {0}", resourceValue ) );
            }
            else
            {
               Display( String::Format( "resource has not changed {0}", resourceValue ) );
            }
         }
         finally
         {
            
            // Ensure that the lock is released.
            rwl->ReleaseReaderLock();
         }

      }
      catch ( ApplicationException^ ) 
      {
         
         // The reader lock request timed out.
         Interlocked::Increment( readerTimeouts );
      }

   }



...
};

// The complete code is located in the ReaderWriterLock
// class topic.
import System.*;
import System.Threading.*;
import System.Threading.Thread;    

public class Test
{
    // Declaring the ReaderWriterLock at the class level
    // makes it visible to all threads.
    private static ReaderWriterLock rwl = new ReaderWriterLock();

    // For this example, the shared resource protected by the
    // ReaderWriterLock is just an integer.
    private static int resource = 0;

...

    // Shows how to release all locks and later restore
    // the lock state. Shows how to use sequence numbers
    // to determine whether another thread has obtained
    // a writer lock since this thread last accessed the
    // resource.
    static void ReleaseRestore(int timeOut)
    {
        int lastWriter;

        try {
            rwl.AcquireReaderLock(timeOut);
            try {
                // It is safe for this thread to read from
                // the shared resource. Cache the value. (You
                // might do this if reading the resource is
                // an expensive operation.)
                int resourceValue = resource;

                Display(("reads resource value " + resourceValue));
                Interlocked.Increment(reads);

                // Save the current writer sequence number.
                lastWriter = rwl.get_WriterSeqNum();

                // Release the lock, and save a cookie so the
                // lock can be restored later.
                LockCookie lc = rwl.ReleaseLock();

                // Wait for a random interval (up to a 
                // quarter of a second), and then restore
                // the previous state of the lock. Note that
                // there is no time-out on the Restore method.
                Thread.Sleep(rnd.Next(250));
                rwl.RestoreLock(lc);

                // Check whether other threads obtained the
                // writer lock in the interval. If not, then
                // the cached value of the resource is still
                // valid.
                if (rwl.AnyWritersSince(lastWriter)) {
                    resourceValue = resource;
                    Interlocked.Increment(reads);
                    Display(("resource has changed " + resourceValue));
                }
                else {
                    Display(("resource has not changed " + resourceValue));
                }
            }
            finally {
                // Ensure that the lock is released.
                rwl.ReleaseReaderLock();
            }
        }
        catch (ApplicationException exp) {
            // The reader lock request timed out.
            Interlocked.Increment(readerTimeouts);
        }
    } //ReleaseRestore

...
}

Plattformen

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Versionsinformationen

.NET Framework

Unterstützt in: 2.0, 1.1, 1.0

Siehe auch

Referenz

ReaderWriterLock-Klasse
ReaderWriterLock-Member
System.Threading-Namespace

Weitere Ressourcen

Verwaltetes Threading
Lese-/Schreibsperren