ReaderWriterLock.UpgradeToWriterLock Método

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

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

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public System.Threading.LockCookie UpgradeToWriterLock (int millisecondsTimeout);

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

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
member this.UpgradeToWriterLock : int -> System.Threading.LockCookie

Public Function UpgradeToWriterLock (millisecondsTimeout As Integer) As LockCookie

Parámetros

Devoluciones

LockCookie

Valor LockCookie.

Atributos

UnsupportedOSPlatformAttribute

Excepciones

Ejemplos

En el ejemplo de código siguiente se muestra cómo solicitar un bloqueo de lector, actualizar el bloqueo del lector a un bloqueo de escritor y cambiar de nuevo a un bloqueo de lector.

Este código forma parte de un ejemplo más grande proporcionado para la ReaderWriterLock clase .

// 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 request a reader lock, upgrade the
// reader lock to the writer lock, and downgrade to a
// reader lock again.
static void UpgradeDowngrade( Random^ rnd, int timeOut )
{
   try
   {
      rwl->AcquireReaderLock( timeOut );
      try
      {

         // It is safe for this thread to read from
         // the shared resource.
         Display( String::Format( "reads resource value {0}", resource ) );
         Interlocked::Increment( reads );

         // If it is necessary to write to the resource,
         // you must either release the reader lock and
         // then request the writer lock, or upgrade the
         // reader lock. Note that 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 is safe for this thread to read or write
               // from the shared resource.
               resource = rnd->Next( 500 );
               Display( String::Format( "writes resource value {0}", resource ) );
               Interlocked::Increment( writes );
            }
            finally
            {

               // Ensure that the lock is released.
               rwl->DowngradeFromWriterLock( lc );
            }

         }
         catch ( ApplicationException^ )
         {

            // The upgrade request timed out.
            Interlocked::Increment( writerTimeouts );
         }


         // When the lock has been downgraded, it is
         // still safe to read from the resource.
         Display( String::Format( "reads resource value {0}", resource ) );
         Interlocked::Increment( reads );
      }
      finally
      {

         // Ensure that the lock is released.
         rwl->ReleaseReaderLock();
      }

   }
   catch ( ApplicationException^ )
   {

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

}

// 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

Comentarios

Cuando un subproceso llama UpgradeToWriterLock al bloqueo del lector, independientemente del recuento de bloqueos, y el subproceso va al final de la cola para el bloqueo del escritor. Por lo tanto, otros subprocesos pueden escribir en el recurso antes de que se conceda al bloqueo de escritura el subproceso que solicitó la actualización.

Para restaurar el estado de bloqueo, llame a DowngradeFromWriterLock mediante el LockCookie devuelto por UpgradeToWriterLock. No lo use LockCookie con RestoreLock.

Cuando un subproceso no tiene ningún bloqueo de lector, no use UpgradeToWriterLock. Utilice AcquireWriterLock en su lugar.

Para conocer los valores de tiempo de espera válidos, vea ReaderWriterLock.

Consulte también

• Subprocesamiento administrado
• ReaderWriterLock

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

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

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public System.Threading.LockCookie UpgradeToWriterLock (TimeSpan timeout);

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

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
member this.UpgradeToWriterLock : TimeSpan -> System.Threading.LockCookie

Public Function UpgradeToWriterLock (timeout As TimeSpan) As LockCookie

Parámetros

Devoluciones

LockCookie

Valor LockCookie.

Atributos

UnsupportedOSPlatformAttribute

Excepciones

Comentarios

Cuando un subproceso llama UpgradeToWriterLock al bloqueo del lector, independientemente del recuento de bloqueos, y el subproceso va al final de la cola para el bloqueo del escritor. Por lo tanto, otros subprocesos pueden escribir en el recurso antes de que se conceda al bloqueo de escritura el subproceso que solicitó la actualización.

Para restaurar el estado de bloqueo, llame a DowngradeFromWriterLock mediante el LockCookie devuelto por UpgradeToWriterLock. No lo use LockCookie con RestoreLock.

Cuando un subproceso no tiene ningún bloqueo de lector, no use UpgradeToWriterLock. Utilice AcquireWriterLock en su lugar.

Para conocer los valores de tiempo de espera válidos, vea ReaderWriterLock.

Consulte también

• Subprocesamiento administrado
• ReaderWriterLock