ReaderWriterLock Класс

Определение

Определяет блокировку, которая поддерживает один пишущий поток и несколько читающих.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
Наследование
ReaderWriterLock
Атрибуты

Примеры

В следующем примере демонстрируется использование ReaderWriterLock для защиты общего ресурса, целочисленного значения с именем resource, которое считывается параллельно и записывается в монопольном режиме несколькими потоками.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. Обратите внимание ReaderWriterLock , что объявляется на уровне класса, чтобы он был видим для всех потоков.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

Комментарии

Важно!

Класс .NET Framework.NET Framework использует две блокировки чтения и записи: ReaderWriterLockSlim и ReaderWriterLock.The .NET Framework.NET Framework has two reader-writer locks, ReaderWriterLockSlim and ReaderWriterLock. Мы рекомендуем применять ReaderWriterLockSlim при любых новых разработках.ReaderWriterLockSlim is recommended for all new development. ReaderWriterLockSlim действует так же, как и ReaderWriterLock, но с более простыми правилами рекурсии и изменения состояния блокировки.ReaderWriterLockSlim is similar to ReaderWriterLock, but it has simplified rules for recursion and for upgrading and downgrading lock state. ReaderWriterLockSlim позволяет избежать многих ситуаций взаимоблокировки.ReaderWriterLockSlim avoids many cases of potential deadlock. Кроме того, производительность ReaderWriterLockSlim значительно выше, чем у ReaderWriterLock.In addition, the performance of ReaderWriterLockSlim is significantly better than ReaderWriterLock.

ReaderWriterLockиспользуется для синхронизации доступа к ресурсу.ReaderWriterLock is used to synchronize access to a resource. В любой момент времени он допускает одновременный доступ на чтение для нескольких потоков или доступ для записи для одного потока.At any given time, it allows either concurrent read access for multiple threads, or write access for a single thread. В ситуации, когда ресурс изменяется редко, ReaderWriterLock обеспечивает лучшую пропускную способность, чем простая односторонняя блокировка, Monitorнапример.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.

ReaderWriterLockлучше всего подходит для большинства операций чтения, в то время как операции записи происходят редко и имеют короткий промежуток времени.ReaderWriterLock works best where most accesses are reads, while writes are infrequent and of short duration. Несколько модулей чтения могут быть альтернативными для одного модуля записи, чтобы ни читатели, ни модули записи не блокировались в течение длительных периодов.Multiple readers alternate with single writers, so that neither readers nor writers are blocked for long periods.

Примечание

Хранение блокировок чтения или записи в течение длительных периодов приведет к нехватки других потоков.Holding reader locks or writer locks for long periods will starve other threads. Для достижения оптимальной производительности рассмотрите возможность реструктуризации приложения, чтобы максимально сокращать продолжительность операций записи.For best performance, consider restructuring your application to minimize the duration of writes.

Поток может содержать блокировку чтения или пишущую блокировку, но не оба одновременно.A thread can hold a reader lock or a writer lock, but not both at the same time. Вместо освобождения блокировки чтения для получения блокировки записи можно использовать UpgradeToWriterLock и. DowngradeFromWriterLockInstead of releasing a reader lock in order to acquire the writer lock, you can use UpgradeToWriterLock and DowngradeFromWriterLock.

Рекурсивные запросы на блокировку увеличивают счетчик блокировок для блокировки.Recursive lock requests increase the lock count on a lock.

Читатели и модули записи помещаются в очередь отдельно.Readers and writers are queued separately. Когда поток освобождает блокировку записи, все потоки, ожидающие в очереди чтения на этом мгновенных, получают блокировки чтения. когда все эти блокировки чтения были освобождены, следующий поток, ожидающий в очереди модуля записи (если таковой имеется), получит блокировку записи и т. д.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. Другими словами, ReaderWriterLock альтернативы между набором читателей и одним модулем записи.In other words, ReaderWriterLock alternates between a collection of readers, and one writer.

Пока поток в очереди модуля записи ожидает освобождения активных блокировок модуля чтения, потоки, запрашивающие новые блокировки модуля чтения, накапливаются в очереди чтения.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. Их запросы не предоставляются, несмотря на то, что они могут совместно использовать параллельный доступ с существующими держателями блокировки чтения. Это помогает защитить модули записи от неопределенной блокировки читателями.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.

Большинство методов для получения блокировок для ReaderWriterLock значений времени ожидания принятия.Most methods for acquiring locks on a ReaderWriterLock accept time-out values. Используйте время ожидания, чтобы избежать взаимоблокировок в приложении.Use time-outs to avoid deadlocks in your application. Например, поток может получить блокировку записи на один ресурс, а затем запросить блокировку чтения на втором ресурсе. в то же время другой поток может получить блокировку записи на второй ресурс и запросить блокировку чтения на первом.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. Если время ожидания не используется, потоки взаимоблокируются.Unless time-outs are used, the threads deadlock.

Если интервал времени ожидания истекает и запрос блокировки не был предоставлен, метод возвращает управление вызывающему потоку, вызывая исключение ApplicationException.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. Поток может перехватить это исключение и определить, какое действие следует предпринять далее.A thread can catch this exception and determine what action to take next.

Время ожидания выражается в миллисекундах.Time-outs are expressed in milliseconds. При использовании System.TimeSpan для указания времени ожидания используется значение, равное общему количеству целых миллисекунд, представленному TimeSpan.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. В следующей таблице показаны допустимые значения времени ожидания в миллисекундах.The following table shows the valid time-out values in milliseconds.

ЗначениеValue ОписаниеDescription
-1-1 Поток ожидает, пока блокировка не будет получена, независимо от того, сколько времени занимает.The thread waits until the lock is acquired, regardless of how long it takes. Для методов, указывающих целочисленное время ожидания, можно Infinite использовать константу.For methods that specify integer time-outs, the constant Infinite can be used.
00 Поток не ждет получения блокировки.The thread does not wait to acquire the lock. Если блокировка не может быть получена немедленно, метод возвращает значение.If the lock cannot be acquired immediately, the method returns.
>0>0 Время ожидания в миллисекундах.The number of milliseconds to wait.

За исключением-1, отрицательные значения времени ожидания не допускаются.With the exception of -1, negative time-out values are not allowed. Если указать отрицательное целое число, отличное от-1, вместо него будет использоваться нулевое значение времени ожидания.If you specify a negative integer other than -1, a time-out value of zero is used instead. (То есть метод возвращается без ожидания, если блокировка не может быть получена немедленно.) Если указано значение TimeSpan , представляющее отрицательное число миллисекунд, отличных от-1, ArgumentOutOfRangeException выдается исключение.(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.

Конструкторы

ReaderWriterLock()

Инициализирует новый экземпляр класса ReaderWriterLock.Initializes a new instance of the ReaderWriterLock class.

Свойства

IsReaderLockHeld

Возвращает значение, указывающее, владеет ли текущий поток блокировкой чтения.Gets a value indicating whether the current thread holds a reader lock.

IsWriterLockHeld

Возвращает значение, указывающее, владеет ли текущий поток блокировкой записи.Gets a value indicating whether the current thread holds the writer lock.

WriterSeqNum

Возвращает текущий последовательный номер.Gets the current sequence number.

Методы

AcquireReaderLock(Int32)

Получает блокировку чтения, используя значение Int32 для задания времени ожидания.Acquires a reader lock, using an Int32 value for the time-out.

AcquireReaderLock(TimeSpan)

Получает блокировку чтения с указанием времени ожидания значением TimeSpan.Acquires a reader lock, using a TimeSpan value for the time-out.

AcquireWriterLock(Int32)

Получает блокировку записи с указанием времени ожидания значением Int32.Acquires the writer lock, using an Int32 value for the time-out.

AcquireWriterLock(TimeSpan)

Получает блокировку записи с указанием времени ожидания значением TimeSpan.Acquires the writer lock, using a TimeSpan value for the time-out.

AnyWritersSince(Int32)

Показывает, была ли предоставлена блокировка записи какому-либо потоку со времени получения последовательного номера.Indicates whether the writer lock has been granted to any thread since the sequence number was obtained.

DowngradeFromWriterLock(LockCookie)

Возвращает состояние блокировки потока к тому, которое было до вызова метода UpgradeToWriterLock(Int32).Restores the lock status of the thread to what it was before UpgradeToWriterLock(Int32) was called.

Equals(Object)

Определяет, равен ли заданный объект текущему объекту.Determines whether the specified object is equal to the current object.

(Унаследовано от Object)
Finalize()

Обеспечивает освобождение ресурсов и выполнение других завершающих операций, когда сборщик мусора восстанавливает объект ReaderWriterLock.Ensures that resources are freed and other cleanup operations are performed when the garbage collector reclaims the ReaderWriterLock object.

GetHashCode()

Служит хэш-функцией по умолчанию.Serves as the default hash function.

(Унаследовано от Object)
GetType()

Возвращает объект Type для текущего экземпляра.Gets the Type of the current instance.

(Унаследовано от Object)
MemberwiseClone()

Создает неполную копию текущего объекта Object.Creates a shallow copy of the current Object.

(Унаследовано от Object)
ReleaseLock()

Освобождает блокировку, независимо от количества ее получений потоком.Releases the lock, regardless of the number of times the thread acquired the lock.

ReleaseReaderLock()

Уменьшает на единицу счетчик блокировок.Decrements the lock count.

ReleaseWriterLock()

Уменьшает на единицу счетчик блокировок данной блокировки записи.Decrements the lock count on the writer lock.

RestoreLock(LockCookie)

Возвращает состояние блокировки потока к тому, которое было до вызова метода ReleaseLock().Restores the lock status of the thread to what it was before calling ReleaseLock().

ToString()

Возвращает строку, представляющую текущий объект.Returns a string that represents the current object.

(Унаследовано от Object)
UpgradeToWriterLock(Int32)

Повышает уровень блокировки чтения до блокировки записи с указанием времени ожидания значением Int32.Upgrades a reader lock to the writer lock, using an Int32 value for the time-out.

UpgradeToWriterLock(TimeSpan)

Повышает уровень блокировки чтения до блокировки записи с указанием времени ожидания значением TimeSpan.Upgrades a reader lock to the writer lock, using a TimeSpan value for the time-out.

Применяется к

Потокобезопасность

Данный тип потокобезопасен.This type is thread safe.

Дополнительно