다음을 통해 공유


ReaderWriterLock.AnyWritersSince(Int32) 메서드

정의

시퀀스 번호를 가져온 다음 임의의 스레드에 작성기 잠금이 부여되었는지 여부를 나타냅니다.

public:
 bool AnyWritersSince(int seqNum);
public bool AnyWritersSince (int seqNum);
member this.AnyWritersSince : int -> bool
Public Function AnyWritersSince (seqNum As Integer) As Boolean

매개 변수

seqNum
Int32

시퀀스 번호입니다.

반환

Boolean

시퀀스 번호를 가져온 다음 임의의 스레드에 작성기 잠금이 부여된 경우 true이고, 그렇지 않으면 false입니다.

예제

다음 코드 예제에서는 메서드 및 WriterSeqNum 속성을 사용하여 AnyWritersSince 현재 스레드가 마지막으로 기록기 잠금을 유지한 이후 다른 스레드가 보호된 리소스에 대한 기록기 잠금을 획득했는지 여부를 확인하는 방법을 보여 있습니다.

이 코드는 클래스에 제공된 더 큰 예제의 ReaderWriterLock 일부입니다.

// 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

설명

사용할 수 있습니다 WriterSeqNumAnyWritersSince 애플리케이션 성능을 향상 시키기 위해. 예를 들어 스레드는 판독기 잠금을 보유하는 동안 얻은 정보를 캐시할 수 있습니다. 잠금을 해제한 후 나중에 잠금을 다시 확인한 후 스레드는 다른 스레드가 중간에 리소스에 기록되었는지 여부를 확인하는 데 사용할 AnyWritersSince 수 있습니다. 그렇지 않은 경우 캐시된 정보를 사용할 수 있습니다. 이 기술은 잠금으로 보호되는 정보를 읽는 데 비용이 많이 드는 경우에 유용합니다. 예를 들어 데이터베이스 쿼리를 실행합니다.

시퀀스 번호가 유용하려면 호출자가 판독기 잠금 또는 기록기 잠금을 보유해야 합니다.

적용 대상

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