ReaderWriterLock.UpgradeToWriterLock Método

public:
 System::Threading::LockCookie UpgradeToWriterLock(int millisecondsTimeout);

public System.Threading.LockCookie UpgradeToWriterLock(int millisecondsTimeout);

member this.UpgradeToWriterLock : int -> System.Threading.LockCookie

Public Function UpgradeToWriterLock (millisecondsTimeout As Integer) As LockCookie

Parâmetros

Devoluções

Um valor de LockCookie.

Exceções

Exemplos

O exemplo de código seguinte mostra como solicitar um bloqueio de leitor, atualizar o bloqueio de leitor para um bloqueio de escritor e fazer downgrade para bloqueio de leitor novamente.

Este código faz parte de um exemplo mais amplo fornecido para a ReaderWriterLock turma.

// 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

Observações

Quando um fio chama UpgradeToWriterLock , o bloqueio leitor é libertado, independentemente do número de bloqueios, e o fio vai para o fim da fila para o bloqueio escritor. Assim, outros threads podem escrever no recurso antes de o thread que solicitou a atualização receber o bloqueio de escritor.

Para restaurar o estado de bloqueio, chame DowngradeFromWriterLock usando o LockCookie retorno por UpgradeToWriterLock. Não use isto LockCookie com RestoreLock.

Quando uma thread não tem bloqueio de leitor, não use UpgradeToWriterLock. Utilize AcquireWriterLock em substituição.

Para valores válidos de time-out, veja ReaderWriterLock.

Ver também

• de threading gerenciado
• ReaderWriterLock

public:
 System::Threading::LockCookie UpgradeToWriterLock(TimeSpan timeout);

public System.Threading.LockCookie UpgradeToWriterLock(TimeSpan timeout);

member this.UpgradeToWriterLock : TimeSpan -> System.Threading.LockCookie

Public Function UpgradeToWriterLock (timeout As TimeSpan) As LockCookie

Parâmetros

Devoluções

Um valor de LockCookie.

Exceções

Observações

Quando um fio chama UpgradeToWriterLock , o bloqueio leitor é libertado, independentemente do número de bloqueios, e o fio vai para o fim da fila para o bloqueio escritor. Assim, outros threads podem escrever no recurso antes de o thread que solicitou a atualização receber o bloqueio de escritor.

Para restaurar o estado de bloqueio, chame DowngradeFromWriterLock usando o LockCookie retorno por UpgradeToWriterLock. Não use isto LockCookie com RestoreLock.

Quando uma thread não tem bloqueio de leitor, não use UpgradeToWriterLock. Utilize AcquireWriterLock em substituição.

Para valores válidos de time-out, veja ReaderWriterLock.

Ver também

• de threading gerenciado
• ReaderWriterLock