ReaderWriterLock.UpgradeToWriterLock Metod

Källa:

ReaderWriterLock.cs

Källa:

ReaderWriterLock.cs

Källa:

ReaderWriterLock.cs

Källa:

ReaderWriterLock.cs

Källa:

ReaderWriterLock.cs

public:
 System::Threading::LockCookie UpgradeToWriterLock(int millisecondsTimeout);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public System.Threading.LockCookie UpgradeToWriterLock(int millisecondsTimeout);

public System.Threading.LockCookie UpgradeToWriterLock(int millisecondsTimeout);

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
member this.UpgradeToWriterLock : int -> System.Threading.LockCookie

member this.UpgradeToWriterLock : int -> System.Threading.LockCookie

Public Function UpgradeToWriterLock (millisecondsTimeout As Integer) As LockCookie

Parametrar

Returer

Ett LockCookie värde.

Attribut

UnsupportedOSPlatformAttribute

Undantag

Exempel

Följande kodexempel visar hur du begär ett läsarlås, uppgraderar läsarlåset till ett skrivlås och nedgraderar till ett läsarlås igen.

Den här koden är en del av ett större exempel som tillhandahålls ReaderWriterLock för klassen.

// 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

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

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

}

End Module

Kommentarer

När en tråd anropar UpgradeToWriterLock läslåset släpps, oavsett låsantal, och tråden går till slutet av kön för skrivarlåset. Därför kan andra trådar skriva till resursen innan tråden som begärde uppgraderingen beviljas skrivarlåset.

Om du vill återställa låstillståndet anropar du DowngradeFromWriterLock med hjälp av returnerade LockCookie av UpgradeToWriterLock. Använd inte detta LockCookie med RestoreLock.

När en tråd inte har något läslås ska du inte använda UpgradeToWriterLock. Använd AcquireWriterLock i stället.

Giltiga timeout-värden finns i ReaderWriterLock.

Se även

• hanterad trådning
• ReaderWriterLock

Källa:

ReaderWriterLock.cs

Källa:

ReaderWriterLock.cs

Källa:

ReaderWriterLock.cs

Källa:

ReaderWriterLock.cs

Källa:

ReaderWriterLock.cs

public:
 System::Threading::LockCookie UpgradeToWriterLock(TimeSpan timeout);

[System.Runtime.Versioning.UnsupportedOSPlatform("browser")]
public System.Threading.LockCookie UpgradeToWriterLock(TimeSpan timeout);

public System.Threading.LockCookie UpgradeToWriterLock(TimeSpan timeout);

[<System.Runtime.Versioning.UnsupportedOSPlatform("browser")>]
member this.UpgradeToWriterLock : TimeSpan -> System.Threading.LockCookie

member this.UpgradeToWriterLock : TimeSpan -> System.Threading.LockCookie

Public Function UpgradeToWriterLock (timeout As TimeSpan) As LockCookie

Parametrar

Returer

Ett LockCookie värde.

Attribut

UnsupportedOSPlatformAttribute

Undantag

Kommentarer

När en tråd anropar UpgradeToWriterLock läslåset släpps, oavsett låsantal, och tråden går till slutet av kön för skrivarlåset. Därför kan andra trådar skriva till resursen innan tråden som begärde uppgraderingen beviljas skrivarlåset.

Om du vill återställa låstillståndet anropar du DowngradeFromWriterLock med hjälp av returnerade LockCookie av UpgradeToWriterLock. Använd inte detta LockCookie med RestoreLock.

När en tråd inte har något läslås ska du inte använda UpgradeToWriterLock. Använd AcquireWriterLock i stället.

Giltiga timeout-värden finns i ReaderWriterLock.

Se även

• hanterad trådning
• ReaderWriterLock