ReaderWriterLock.RestoreLock(LockCookie) Yöntem

Tanım

Ad Alanı:

System.Threading

Bütünleştirilmiş Kod:

System.Threading.dll

Kaynak:

ReaderWriterLock.cs

İş parçacığının kilit durumunu çağırmadan ReleaseLock()önceki durumuna geri yükler.

public:
 void RestoreLock(System::Threading::LockCookie % lockCookie);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public void RestoreLock (ref System.Threading.LockCookie lockCookie);

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
member this.RestoreLock : LockCookie -> unit

Public Sub RestoreLock (ByRef lockCookie As LockCookie)

Parametreler

lockCookie

LockCookie

LockCookie tarafından ReleaseLock()döndürülen.

Öznitelikler

UnsupportedOSPlatformAttribute

Özel durumlar

NullReferenceException

adresi lockCookie null işaretçidir.

Örnekler

Aşağıdaki kod örneği, iş parçacığı tarafından kaç kez alındığına bakılmaksızın kilidi serbest bırakmak için yönteminin nasıl kullanılacağını ReleaseLock ve daha sonra kilidin durumunun nasıl geri yüklendiğini gösterir.

Bu kod, sınıfı için ReaderWriterLock sağlanan daha büyük bir örneğin parçasıdır.

// 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;

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

public class Example
{
   static ReaderWriterLock rwl = new ReaderWriterLock();
   // Define the shared resource protected by the ReaderWriterLock.
   static int resource = 0;

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

Public Module Example
   Private rwl As New ReaderWriterLock()
   ' Define the shared resource protected by the ReaderWriterLock.
   Private 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.
static void ReleaseRestore( Random^ rnd, 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 );
   }

}

// Release all locks and later restores the lock state.
// Uses sequence numbers to determine whether another thread has
// obtained a writer lock since this thread last accessed the resource.
static void ReleaseRestore(Random rnd, int timeOut)
{
   int lastWriter;

   try {
      rwl.AcquireReaderLock(timeOut);
      try {
         // It's safe for this thread to read from the shared resource,
         // so read and cache the resource value.
         int resourceValue = resource;     // Cache the resource value.
         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 and then restore the previous state of the lock.
         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);
   }
}

' Release all locks and later restores the lock state.
' Uses sequence numbers to determine whether another thread has
' obtained a writer lock since this thread last accessed the resource.
Sub ReleaseRestore(rnd As Random ,timeOut As Integer)
   Dim lastWriter As Integer
   
   Try
      rwl.AcquireReaderLock(timeOut)
      Try
         ' It's safe for this thread to read from the shared resource,
         ' so read and cache the resource value.
         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 and then restore the previous state of the lock.
         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

};

}

End Module

Açıklamalar

tarafından RestoreLock geri yüklenen durum, özyinelemeli kilit sayısını içerir.

İş parçacığı, başka bir iş parçacığı yazıcı kilidini aldıktan sonra okuyucu kilidini geri yüklemeye çalışırsa veya başka bir iş parçacığı okuyucu kilidi veya yazıcı kilidi aldıktan sonra yazıcı kilidini geri yüklemeyi denerse engeller. RestoreLock Zaman aşımını kabul etmediğinden olası kilitlenmeleri önlemeye dikkat etmelisiniz.

Dikkat

çağrısından RestoreLockönce çağrısından sonra ReleaseLockalınan tüm kilitleri serbest bıraktıklarından emin olun. Örneğin, bir iş parçacığı bir okuyucu kilidi alır ve daha sonra önceki bir yazıcı kilidini geri yüklemeyi denerse kilitlenmeye başlar. Bu tür ek kilitleri algılamak için ve IsWriterLockHeld kullanınIsReaderLockHeld.

'den UpgradeToWriterLockdöndürülen bir LockCookie kullanmayın.

Ayrıca bkz.

• Yönetilen İş Parçacığı Oluşturma
• Readerwriterlock