ReaderWriterLock.DowngradeFromWriterLock(LockCookie) Yöntem

Tanım

Ad Alanı:

System.Threading

Bütünleştirilmiş Kodlar:

netstandard.dll, System.Threading.dll

Kaynak:

ReaderWriterLock.cs

İş parçacığının kilit durumunu daha önce UpgradeToWriterLock(Int32) çağrıldığı duruma geri yükler.

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

public void DowngradeFromWriterLock(ref System.Threading.LockCookie lockCookie);

member this.DowngradeFromWriterLock : LockCookie -> unit

Public Sub DowngradeFromWriterLock (ByRef lockCookie As LockCookie)

Parametreler

lockCookie

LockCookie

tarafından LockCookieUpgradeToWriterLock(Int32)döndürülen.

Özel durumlar

ApplicationException

İş parçacığında yazıcı kilidi yok.

NullReferenceException

adresi lockCookie null bir işaretçidir.

Örnekler

Aşağıdaki kod örneğinde okuyucu kilidi isteme, okuyucu kilidini yazıcı kilidine yükseltme ve okuyucu kilidine yeniden düşürme gösterilmektedir.

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

// 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

// Requests a reader lock, upgrades the reader lock to the writer
// lock, and downgrades it to a reader lock again.
static void UpgradeDowngrade(Random rnd, int timeOut)
{
   try {
      rwl.AcquireReaderLock(timeOut);
      try {
         // It's safe for this thread to read from the shared resource.
         Display("reads resource value " + resource);
         Interlocked.Increment(ref reads);

         // To write to the resource, either release the reader lock and
         // request the writer lock, or upgrade the reader lock. Upgrading
         // the reader lock puts the thread in the write queue, behind any
         // other threads that might be waiting for the writer lock.
         try {
            LockCookie lc = rwl.UpgradeToWriterLock(timeOut);
            try {
               // It's safe for this thread to read or write from the shared resource.
               resource = rnd.Next(500);
               Display("writes resource value " + resource);
               Interlocked.Increment(ref writes);
            }
            finally {
               // Ensure that the lock is released.
               rwl.DowngradeFromWriterLock(ref lc);
            }
         }
         catch (ApplicationException) {
            // The upgrade request timed out.
            Interlocked.Increment(ref writerTimeouts);
         }

         // If the lock was downgraded, it's still safe to read from the resource.
         Display("reads resource value " + resource);
         Interlocked.Increment(ref reads);
      }
      finally {
         // Ensure that the lock is released.
         rwl.ReleaseReaderLock();
      }
   }
   catch (ApplicationException) {
      // The reader lock request timed out.
      Interlocked.Increment(ref readerTimeouts);
   }
}

' Requests a reader lock, upgrades the reader lock to the writer
' lock, and downgrades it to a reader lock again.
Sub UpgradeDowngrade(rnd As Random, timeOut As Integer)
   Try
      rwl.AcquireReaderLock(timeOut)
      Try
         ' It's safe for this thread to read from the shared resource.
         Display("reads resource value " & resource)
         Interlocked.Increment(reads)
         
         ' To write to the resource, either release the reader lock and
         ' request the writer lock, or upgrade the reader lock. Upgrading
         ' the reader lock puts the thread in the write queue, behind any
         ' other threads that might be waiting for the writer lock.
         Try
            Dim lc As LockCookie = rwl.UpgradeToWriterLock(timeOut)
            Try
               ' It's safe for this thread to read or write from the shared resource.
               resource = rnd.Next(500)
               Display("writes resource value " & resource)
               Interlocked.Increment(writes)
            Finally
               ' Ensure that the lock is released.
               rwl.DowngradeFromWriterLock(lc)
            End Try
         Catch ex As ApplicationException
            ' The upgrade request timed out.
            Interlocked.Increment(writerTimeouts)
         End Try
         
         ' If the lock was downgraded, it's still safe to read from the resource.
         Display("reads resource value " & resource)
         Interlocked.Increment(reads)
      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

DowngradeFromWriterLock özyinelemeli kilit sayısına bakılmaksızın yazıcı kilidini serbest bırakır ve yazıcı kilidine yükseltmeden önce iş parçacığı tarafından tutulan okuyucu kilidini geri yükler. Okuyucu kilidindeki kilit sayısı geri yüklenir.

Note

DowngradeFromWriterLockçağrılarak LockCookieelde edilen bir UpgradeToWriterLock kabul eder. tarafından LockCookiedöndürülen bir ReleaseLock kullanmayın.

Yazıcı kilidi serbest bırakıldığında tüm okuyucu kilidi istekleri verildiğinden, diğer iş parçacıkları yazıcı kilidini bekliyor olsa bile, bir iş parçacığı yazıcı kilidinden indirilirken engellenmez.

Ayrıca bkz.

• Yönetilen İş Parçacıkları