ReaderWriterLock.AnyWritersSince(Int32) 메서드

정의

시퀀스 번호를 가져온 다음 임의의 스레드에 작성기 잠금이 부여되었는지 여부를 나타냅니다.Indicates whether the writer lock has been granted to any thread since the sequence number was obtained.

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.The sequence number.

반환

Boolean

시퀀스 번호를 가져온 다음 임의의 스레드에 작성기 잠금이 부여된 경우 true이고, 그렇지 않으면 false입니다.true if the writer lock has been granted to any thread since the sequence number was obtained; otherwise, false.

예제

다음 코드 예제에서는 메서드 및 속성을 사용 하 여 AnyWritersSince WriterSeqNum 현재 스레드가 마지막으로 작성기 잠금을 보유 한 이후 보호 된 리소스에 대해 다른 스레드에서 작성기 잠금을 가져왔는지 여부를 확인 하는 방법을 보여 줍니다.The following code example shows how to use the AnyWritersSince method and the WriterSeqNum property to determine whether another thread acquired the writer lock on the protected resource since the current thread last held the writer lock.

이 코드는 클래스에 대해 제공 된 더 큰 예제의 일부입니다 ReaderWriterLock .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

설명

사용할 수 있습니다 WriterSeqNumAnyWritersSince 애플리케이션 성능을 향상 시키기 위해.You can use WriterSeqNum and AnyWritersSince to improve application performance. 예를 들어 스레드가 판독기 잠금을 보유 하는 동안 가져오는 정보를 캐시할 수 있습니다.For example, a thread might cache the information it obtains while holding a reader lock. 해제 후 나중에 잠금을 reacquiring 스레드는를 사용 하 여 AnyWritersSince 다른 스레드가 임시의 리소스에 기록 되었는지 여부를 확인할 수 있습니다. 그렇지 않은 경우에는 캐시 된 정보를 사용할 수 있습니다.After releasing and later reacquiring the lock, the thread can use AnyWritersSince to determine whether other threads have written to the resource in the interim; if not, the cached information can be used. 이 기법은 잠금으로 보호 되는 정보를 읽는 데 비용이 많이 드는 경우에 유용 합니다. 예를 들어 데이터베이스 쿼리를 실행 합니다.This technique is useful where reading the information protected by the lock is expensive; for example, running a database query.

시퀀스 번호가 유용 하려면 호출자가 판독기 잠금이나 작성기 잠금을 보유 해야 합니다.The caller must be holding a reader lock or a writer lock in order for the sequence number to be useful.

적용 대상

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