ReaderWriterLock.RestoreLock(LockCookie) Método

Definición

Restaura el estado de bloqueo del subproceso al estado que tenía antes de llamar a ReleaseLock().Restores the lock status of the thread to what it was before calling ReleaseLock().

public:
 void RestoreLock(System::Threading::LockCookie % lockCookie);
public void RestoreLock (ref System.Threading.LockCookie lockCookie);
member this.RestoreLock : LockCookie -> unit
Public Sub RestoreLock (ByRef lockCookie As LockCookie)

Parámetros

lockCookie
LockCookie

Un LockCookie devuelto por ReleaseLock().A LockCookie returned by ReleaseLock().

Excepciones

La dirección de lockCookie es un puntero nulo.The address of lockCookie is a null pointer.

Ejemplos

En el ejemplo de código siguiente se muestra cómo utilizar el ReleaseLock método para liberar el bloqueo, independientemente del número de veces que el subproceso haya adquirido y cómo restaurar el estado del bloqueo más adelante.The following code example shows how to use the ReleaseLock method to release the lock, regardless of how many times it has been acquired by the thread, and how to restore the state of the lock later.

Este código forma parte de un ejemplo más extenso proporcionado para la ReaderWriterLock clase.This code is part of a larger example provided for the ReaderWriterLock class.

// 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

Comentarios

El estado restaurado por RestoreLock incluye el recuento de bloqueos recursivos.The state restored by RestoreLock includes the recursive lock count.

Un subproceso se bloquea si intenta restaurar un bloqueo de lector después de que otro subproceso haya adquirido el bloqueo de escritor, o si intenta restaurar el bloqueo de escritor después de que otro subproceso haya adquirido un bloqueo de lector o escritor.A thread blocks if it tries to restore a reader lock after another thread has acquired the writer lock, or if it tries to restore the writer lock after another thread has acquired a reader lock or writer lock. Dado RestoreLock que no acepta un tiempo de espera, debe tener cuidado de evitar posibles interbloqueos.Because RestoreLock does not accept a time-out, you should take care to avoid possible deadlocks.

Precaución

Antes RestoreLock de llamar a, asegúrese de que ha liberado todos los bloqueos adquiridos desde la llamada a ReleaseLock .Before calling RestoreLock, make sure you have released all locks acquired since the call to ReleaseLock. Por ejemplo, un subproceso se bloquea si adquiere un bloqueo de lector y, a continuación, intenta restaurar un bloqueo de escritor anterior.For example, a thread deadlocks if it acquires a reader lock, and then attempts to restore an earlier writer lock. Use IsReaderLockHeld y IsWriterLockHeld para detectar estos bloqueos adicionales.Use IsReaderLockHeld and IsWriterLockHeld to detect such additional locks.

No utilice un LockCookie devuelto de UpgradeToWriterLock .Do not use a LockCookie returned from UpgradeToWriterLock.

Se aplica a