ReaderWriterLock ReaderWriterLock ReaderWriterLock ReaderWriterLock Class

Definición

Define un bloqueo que admite un escritor y varios lectores.Defines a lock that supports single writers and multiple readers.

public ref class ReaderWriterLock sealed : System::Runtime::ConstrainedExecution::CriticalFinalizerObject
[System.Runtime.InteropServices.ComVisible(true)]
public sealed class ReaderWriterLock : System.Runtime.ConstrainedExecution.CriticalFinalizerObject
type ReaderWriterLock = class
    inherit CriticalFinalizerObject
Public NotInheritable Class ReaderWriterLock
Inherits CriticalFinalizerObject
Herencia
ReaderWriterLockReaderWriterLockReaderWriterLockReaderWriterLock
Atributos

Ejemplos

En el ejemplo siguiente se muestra cómo utilizar ReaderWriterLock un para proteger un recurso compartido, un valor entero denominado resource, que se lee simultáneamente y que es escrito exclusivamente por varios subprocesos.The following example demonstrates how to use a ReaderWriterLock to protect a shared resource, an integer value named resource, that is read concurrently and written exclusively by multiple threads. Tenga en cuenta ReaderWriterLock que se declara en el nivel de clase para que sea visible para todos los subprocesos.Note that the ReaderWriterLock is declared at the class level so that it is visible to all threads.

// This example shows a ReaderWriterLock protecting a shared
// resource that is read concurrently and written exclusively
// by multiple threads.
// 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;

   literal int numThreads = 26;
   static bool running = true;
   static Random^ rnd = gcnew Random;

   // Statistics.
   static int readerTimeouts = 0;
   static int writerTimeouts = 0;
   static int reads = 0;
   static int writes = 0;
   static void ThreadProc()
   {
      
      // As long as a thread runs, it randomly selects
      // various ways to read and write from the shared 
      // resource. Each of the methods demonstrates one 
      // or more features of ReaderWriterLock.
      while ( running )
      {
         double action = rnd->NextDouble();
         if ( action < .8 )
                  ReadFromResource( 10 );
         else
         if ( action < .81 )
                  ReleaseRestore( 50 );
         else
         if ( action < .90 )
                  UpgradeDowngrade( 100 );
         else
                  WriteToResource( 100 );
      }
   }


   // Shows how to request and release a reader lock, and
   // how to handle time-outs.
   static void ReadFromResource( 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 );
         }
         finally
         {
            
            // Ensure that the lock is released.
            rwl->ReleaseReaderLock();
         }

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

   }


   // Shows how to request and release the writer lock, and
   // how to handle time-outs.
   static void WriteToResource( int timeOut )
   {
      try
      {
         rwl->AcquireWriterLock( 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->ReleaseWriterLock();
         }

      }
      catch ( ApplicationException^ ) 
      {
         
         // The writer lock request timed out.
         Interlocked::Increment( writerTimeouts );
      }

   }


   // 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( 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 );
      }

   }


   // 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( 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 );
      }

   }


   // Helper method briefly displays the most recent
   // thread action. Comment out calls to Display to 
   // get a better idea of throughput.
   static void Display( String^ msg )
   {
      Console::Write( "Thread {0} {1}.       \r", Thread::CurrentThread->Name, msg );
   }

};


int main()
{
   array<String^>^args = Environment::GetCommandLineArgs();
   
   // Start a series of threads. Each thread randomly
   // performs reads and writes on the shared resource.
   array<Thread^>^t = gcnew array<Thread^>(Test::numThreads);
   for ( int i = 0; i < Test::numThreads; i++ )
   {
      t[ i ] = gcnew Thread( gcnew ThreadStart( Test::ThreadProc ) );
      t[ i ]->Name = gcnew String( Convert::ToChar( i + 65 ),1 );
      t[ i ]->Start();
      if ( i > 10 )
            Thread::Sleep( 300 );

   }
   
   // Tell the threads to shut down, then wait until they all
   // finish.
   Test::running = false;
   for ( int i = 0; i < Test::numThreads; i++ )
   {
      t[ i ]->Join();

   }
   
   // Display statistics.
   Console::WriteLine( "\r\n {0} reads, {1} writes, {2} reader time-outs, {3} writer time-outs.", Test::reads, Test::writes, Test::readerTimeouts, Test::writerTimeouts );
   Console::WriteLine( "Press ENTER to exit." );
   Console::ReadLine();
   return 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;

   const int numThreads = 26;
   static bool running = true;
   static Random rnd = new Random();

   // Statistics.
   static int readerTimeouts = 0;
   static int writerTimeouts = 0;
   static int reads = 0;
   static int writes = 0;

   public static void Main()
   {
      // Start a series of threads to randomly read from and
      // write to the shared resource.
      Thread[] t = new Thread[numThreads];
      for (int i = 0; i < numThreads; i++){
         t[i] = new Thread(new ThreadStart(ThreadProc));
         t[i].Name = new String(Convert.ToChar(i + 65), 1);
         t[i].Start();
         if (i > 10)
            Thread.Sleep(300);
      }

      // Tell the threads to shut down and wait until they all finish.
      running = false;
      for (int i = 0; i < numThreads; i++)
         t[i].Join();

      // Display statistics.
      Console.WriteLine("\n{0} reads, {1} writes, {2} reader time-outs, {3} writer time-outs.",
            reads, writes, readerTimeouts, writerTimeouts);
      Console.Write("Press ENTER to exit... ");
      Console.ReadLine();
   }

   static void ThreadProc()
   {
      // Randomly select a way for the thread to read and write from the shared
      // resource.
      while (running) {
         double action = rnd.NextDouble();
         if (action < .8)
            ReadFromResource(10);
         else if (action < .81)
            ReleaseRestore(50);
         else if (action < .90)
            UpgradeDowngrade(100);
         else
            WriteToResource(100);
      }
   }

   // Request and release a reader lock, and handle time-outs.
   static void ReadFromResource(int timeOut)
   {
      try {
         rwl.AcquireReaderLock(timeOut);
         try {
            // It is safe for this thread to read from the shared 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);
      }
   }

   // Request and release the writer lock, and handle time-outs.
   static void WriteToResource(int timeOut)
   {
      try {
         rwl.AcquireWriterLock(timeOut);
         try {
            // It's safe for this thread to access 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.ReleaseWriterLock();
         }
      }
      catch (ApplicationException) {
         // The writer lock request timed out.
         Interlocked.Increment(ref writerTimeouts);
      }
   }

   // Requests a reader lock, upgrades the reader lock to the writer
   // lock, and downgrades it to a reader lock again.
   static void UpgradeDowngrade(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);
      }
   }

   // 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(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);
      }
   }

   // Helper method briefly displays the most recent thread action.
   static void Display(string msg)
   {
      Console.Write("Thread {0} {1}.       \r", Thread.CurrentThread.Name, msg);
   }
}
' 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

   Const numThreads As Integer = 26
   Private running As Boolean = True
   Private rnd As New Random()
   
   ' Statistics.
   Private readerTimeouts As Integer = 0
   Private writerTimeouts As Integer = 0
   Private reads As Integer = 0
   Private writes As Integer = 0
  
   Public Sub Main()
      ' Start a series of threads to randomly read from and
      ' write to the shared resource.
      Dim t(numThreads - 1) As Thread
      Dim i As Integer
      For i = 0 To numThreads - 1
         t(i) = New Thread(New ThreadStart(AddressOf ThreadProc))
         t(i).Name = Chr(i + 65)
         t(i).Start()
         If i > 10 Then
            Thread.Sleep(300)
         End If
      Next

      ' Tell the threads to shut down and wait until they all finish.
      running = False
      For i = 0 To numThreads - 1
         t(i).Join()
      Next
      
      ' Display statistics.
      Console.WriteLine(vbCrLf & "{0} reads, {1} writes, {2} reader time-outs, {3} writer time-outs.",
                        reads, writes, readerTimeouts, writerTimeouts)
      Console.Write("Press ENTER to exit... ")
      Console.ReadLine()
   End Sub

   Sub ThreadProc()
      ' Randomly select a way for the thread to read and write from the shared
      ' resource.
      While running
         Dim action As Double = rnd.NextDouble()
         If action < 0.8 Then
            ReadFromResource(10)
         ElseIf action < 0.81 Then
            ReleaseRestore(50)
         ElseIf action < 0.9 Then
            UpgradeDowngrade(100)
         Else
            WriteToResource(100)
         End If
      End While
   End Sub
    
   ' Request and release a reader lock, and handle time-outs.
   Sub ReadFromResource(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)
         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

   ' Request and release the writer lock, and handle time-outs.
   Sub WriteToResource(timeOut As Integer)
      Try
         rwl.AcquireWriterLock(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.ReleaseWriterLock()
         End Try
      Catch ex As ApplicationException
         ' The writer lock request timed out.
         Interlocked.Increment(writerTimeouts)
      End Try
   End Sub

   ' Requests a reader lock, upgrades the reader lock to the writer
   ' lock, and downgrades it to a reader lock again.
   Sub UpgradeDowngrade(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

   ' 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(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

   ' Helper method briefly displays the most recent thread action.
   Sub Display(msg As String)
      Console.Write("Thread {0} {1}.       " & vbCr, Thread.CurrentThread.Name, msg)
   End Sub
End Module

Comentarios

Importante

.NET Framework.NET Framework tiene dos bloqueos de lector y escritor, ReaderWriterLockSlim y ReaderWriterLock.The .NET Framework.NET Framework has two reader-writer locks, ReaderWriterLockSlim and ReaderWriterLock. ReaderWriterLockSlim se recomienda para todos los nuevos desarrollos.ReaderWriterLockSlim is recommended for all new development. ReaderWriterLockSlim es similar a ReaderWriterLock, pero se han simplificado las reglas para la recursividad y para actualizar y degradar el estado de bloqueo.ReaderWriterLockSlim is similar to ReaderWriterLock, but it has simplified rules for recursion and for upgrading and downgrading lock state. ReaderWriterLockSlim evita muchos casos de interbloqueo potencial.ReaderWriterLockSlim avoids many cases of potential deadlock. Además, el rendimiento de ReaderWriterLockSlim es significativamente mayor que ReaderWriterLock.In addition, the performance of ReaderWriterLockSlim is significantly better than ReaderWriterLock.

ReaderWriterLockse utiliza para sincronizar el acceso a un recurso.ReaderWriterLock is used to synchronize access to a resource. En un momento dado, permite el acceso de lectura simultáneo para varios subprocesos o el acceso de escritura para un único subproceso.At any given time, it allows either concurrent read access for multiple threads, or write access for a single thread. En una situación en la que un recurso se cambia con poca frecuencia ReaderWriterLock , proporciona un rendimiento mejor que un bloqueo simple a la vez, Monitorcomo.In a situation where a resource is changed infrequently, a ReaderWriterLock provides better throughput than a simple one-at-a-time lock, such as Monitor.

ReaderWriterLockfunciona mejor cuando la mayoría de los accesos son lecturas, mientras que las escrituras son poco frecuentes y de corta duración.ReaderWriterLock works best where most accesses are reads, while writes are infrequent and of short duration. Varios lectores alternativos con escritores únicos, de modo que no se bloqueen lectores ni escritores durante períodos prolongados.Multiple readers alternate with single writers, so that neither readers nor writers are blocked for long periods.

Nota

Mantener los bloqueos de lectura o los bloqueos del escritor durante largos períodos de tiempo privará a otros subprocesos.Holding reader locks or writer locks for long periods will starve other threads. Para obtener el mejor rendimiento, considere la posibilidad de reestructurar la aplicación para minimizar la duración de las escrituras.For best performance, consider restructuring your application to minimize the duration of writes.

Un subproceso puede contener un bloqueo de lector o un bloqueo de escritor, pero no ambos al mismo tiempo.A thread can hold a reader lock or a writer lock, but not both at the same time. En lugar de liberar un bloqueo de lector con el fin de adquirir el bloqueo de escritor, UpgradeToWriterLock puede DowngradeFromWriterLockusar y.Instead of releasing a reader lock in order to acquire the writer lock, you can use UpgradeToWriterLock and DowngradeFromWriterLock.

Las solicitudes de bloqueo recursivo aumentan el número de bloqueos de un bloqueo.Recursive lock requests increase the lock count on a lock.

Los lectores y escritores se ponen en cola por separado.Readers and writers are queued separately. Cuando un subproceso libera el bloqueo de escritor, a todos los subprocesos que esperan en la cola del lector en ese instante se les conceden bloqueos de lectura. Cuando se han liberado todos esos bloqueos de lectura, el siguiente subproceso que espera en la cola del escritor, si existe, tiene concedido el bloqueo de escritor, y así sucesivamente.When a thread releases the writer lock, all threads waiting in the reader queue at that instant are granted reader locks; when all of those reader locks have been released, the next thread waiting in the writer queue, if any, is granted the writer lock, and so on. En otras palabras, ReaderWriterLock alterna entre una colección de lectores y un escritor.In other words, ReaderWriterLock alternates between a collection of readers, and one writer.

Mientras que un subproceso de la cola del escritor está esperando a que se liberen los bloqueos de lectura activos, los subprocesos que solicitan nuevos bloqueos de lectura se acumulan en la cola del lector.While a thread in the writer queue is waiting for active reader locks to be released, threads requesting new reader locks accumulate in the reader queue. No se conceden sus solicitudes, aunque podrían compartir el acceso simultáneo con los titulares de bloqueo de lector existentes; Esto ayuda a proteger a los escritores contra el bloqueo indefinido por los lectores.Their requests are not granted, even though they could share concurrent access with existing reader-lock holders; this helps protect writers against indefinite blockage by readers.

La mayoría de los métodos para adquirir bloqueos en un ReaderWriterLock valor de tiempo de espera de aceptación.Most methods for acquiring locks on a ReaderWriterLock accept time-out values. Utilice los tiempos de espera para evitar los interbloqueos de la aplicación.Use time-outs to avoid deadlocks in your application. Por ejemplo, un subproceso podría adquirir el bloqueo de escritor en un recurso y, a continuación, solicitar un bloqueo de lector en un segundo recurso. mientras tanto, otro subproceso podría adquirir el bloqueo de escritor en el segundo recurso y solicitar un bloqueo de lector en el primero.For example, a thread might acquire the writer lock on one resource and then request a reader lock on a second resource; in the meantime, another thread might acquire the writer lock on the second resource, and request a reader lock on the first. A menos que se usen los tiempos de espera, los subprocesos interbloquean.Unless time-outs are used, the threads deadlock.

Si el intervalo de tiempo de espera expira y no se ha concedido la solicitud de bloqueo, el método devuelve el control al subproceso que ApplicationExceptionrealiza la llamada iniciando.If the time-out interval expires and the lock request has not been granted, the method returns control to the calling thread by throwing an ApplicationException. Un subproceso puede detectar esta excepción y determinar qué acción debe realizarse a continuación.A thread can catch this exception and determine what action to take next.

Los tiempos de espera se expresan en milisegundos.Time-outs are expressed in milliseconds. Si utiliza System.TimeSpan para especificar el tiempo de espera, el valor utilizado es el número total de milisegundos enteros representados TimeSpanpor.If you use a System.TimeSpan to specify the time-out, the value used is the total number of whole milliseconds represented by the TimeSpan. En la tabla siguiente se muestran los valores de tiempo de espera válidos en milisegundos.The following table shows the valid time-out values in milliseconds.

ValorValue DescripciónDescription
-1-1 El subproceso espera hasta que se adquiere el bloqueo, independientemente del tiempo que tarde.The thread waits until the lock is acquired, regardless of how long it takes. En el caso de los métodos que especifican los tiempos de Infinite espera de enteros, se puede usar la constante.For methods that specify integer time-outs, the constant Infinite can be used.
00 El subproceso no espera para adquirir el bloqueo.The thread does not wait to acquire the lock. Si el bloqueo no se puede adquirir inmediatamente, el método devuelve.If the lock cannot be acquired immediately, the method returns.
>0>0 Número de milisegundos durante los que se va a esperar.The number of milliseconds to wait.

Con la excepción de-1, no se permiten valores de tiempo de espera negativos.With the exception of -1, negative time-out values are not allowed. Si especifica un entero negativo distinto de-1, se utiliza en su lugar un valor de tiempo de espera de cero.If you specify a negative integer other than -1, a time-out value of zero is used instead. (Es decir, el método devuelve sin esperar, si el bloqueo no se puede adquirir inmediatamente). Si especifica un TimeSpan que representa un número negativo de milisegundos distinto de-1, ArgumentOutOfRangeException se produce una excepción.(That is, the method returns without waiting, if the lock cannot be acquired immediately.) If you specify a TimeSpan that represents a negative number of milliseconds other than -1, ArgumentOutOfRangeException is thrown.

Constructores

ReaderWriterLock() ReaderWriterLock() ReaderWriterLock() ReaderWriterLock()

Inicializa una nueva instancia de la clase ReaderWriterLock.Initializes a new instance of the ReaderWriterLock class.

Propiedades

IsReaderLockHeld IsReaderLockHeld IsReaderLockHeld IsReaderLockHeld

Obtiene un valor que indica si el subproceso actual tiene el bloqueo de lector.Gets a value indicating whether the current thread holds a reader lock.

IsWriterLockHeld IsWriterLockHeld IsWriterLockHeld IsWriterLockHeld

Obtiene un valor que indica si el subproceso actual tiene el bloqueo de escritor.Gets a value indicating whether the current thread holds the writer lock.

WriterSeqNum WriterSeqNum WriterSeqNum WriterSeqNum

Obtiene el número de secuencia actual.Gets the current sequence number.

Métodos

AcquireReaderLock(Int32) AcquireReaderLock(Int32) AcquireReaderLock(Int32) AcquireReaderLock(Int32)

Adquiere un bloqueo de lector, utilizando un valor Int32 para el tiempo de espera.Acquires a reader lock, using an Int32 value for the time-out.

AcquireReaderLock(TimeSpan) AcquireReaderLock(TimeSpan) AcquireReaderLock(TimeSpan) AcquireReaderLock(TimeSpan)

Adquiere un bloqueo de lector, utilizando un valor TimeSpan para el tiempo de espera.Acquires a reader lock, using a TimeSpan value for the time-out.

AcquireWriterLock(Int32) AcquireWriterLock(Int32) AcquireWriterLock(Int32) AcquireWriterLock(Int32)

Adquiere un bloqueo de escritor, utilizando un valor Int32 para el tiempo de espera.Acquires the writer lock, using an Int32 value for the time-out.

AcquireWriterLock(TimeSpan) AcquireWriterLock(TimeSpan) AcquireWriterLock(TimeSpan) AcquireWriterLock(TimeSpan)

Adquiere un bloqueo de escritor, utilizando un valor TimeSpan para el tiempo de espera.Acquires the writer lock, using a TimeSpan value for the time-out.

AnyWritersSince(Int32) AnyWritersSince(Int32) AnyWritersSince(Int32) AnyWritersSince(Int32)

Indica si se ha concedido el bloqueo de escritor a algún subproceso desde que se obtuvo el número de secuencia.Indicates whether the writer lock has been granted to any thread since the sequence number was obtained.

DowngradeFromWriterLock(LockCookie) DowngradeFromWriterLock(LockCookie) DowngradeFromWriterLock(LockCookie) DowngradeFromWriterLock(LockCookie)

Restaura el estado de bloqueo del subproceso al estado que tenía antes de llamar a UpgradeToWriterLock(Int32).Restores the lock status of the thread to what it was before UpgradeToWriterLock(Int32) was called.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determina si el objeto especificado es igual al objeto actual.Determines whether the specified object is equal to the current object.

(Inherited from Object)
Finalize() Finalize() Finalize() Finalize()

Se asegura de que los recursos se liberan y que se llevan a cabo otras operaciones de limpieza cuando el recolector de elementos no utilizados recupere el objeto ReaderWriterLock.Ensures that resources are freed and other cleanup operations are performed when the garbage collector reclaims the ReaderWriterLock object.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Sirve como la función hash predeterminada.Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Obtiene el Type de la instancia actual.Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Crea una copia superficial del objeto Object actual.Creates a shallow copy of the current Object.

(Inherited from Object)
ReleaseLock() ReleaseLock() ReleaseLock() ReleaseLock()

Libera el bloqueo, independientemente del número de veces que el subproceso haya adquirido el bloqueo.Releases the lock, regardless of the number of times the thread acquired the lock.

ReleaseReaderLock() ReleaseReaderLock() ReleaseReaderLock() ReleaseReaderLock()

Reduce el recuento de bloqueos.Decrements the lock count.

ReleaseWriterLock() ReleaseWriterLock() ReleaseWriterLock() ReleaseWriterLock()

Reduce el recuento de bloqueos del bloqueo de escritor.Decrements the lock count on the writer lock.

RestoreLock(LockCookie) RestoreLock(LockCookie) RestoreLock(LockCookie) RestoreLock(LockCookie)

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().

ToString() ToString() ToString() ToString()

Devuelve una cadena que representa el objeto actual.Returns a string that represents the current object.

(Inherited from Object)
UpgradeToWriterLock(Int32) UpgradeToWriterLock(Int32) UpgradeToWriterLock(Int32) UpgradeToWriterLock(Int32)

Actualiza un bloqueo de lector al bloqueo de escritor, utilizando un valor Int32 para el tiempo de espera.Upgrades a reader lock to the writer lock, using an Int32 value for the time-out.

UpgradeToWriterLock(TimeSpan) UpgradeToWriterLock(TimeSpan) UpgradeToWriterLock(TimeSpan) UpgradeToWriterLock(TimeSpan)

Actualiza un bloqueo de lector al bloqueo de escritor utilizando un valor TimeSpan para el tiempo de espera.Upgrades a reader lock to the writer lock, using a TimeSpan value for the time-out.

Se aplica a

Seguridad para subprocesos

Este tipo es seguro para la ejecución de subprocesos.This type is thread safe.

Consulte también: