ReaderWriterLock.UpgradeToWriterLock 方法

來源:

ReaderWriterLock.cs

來源:

ReaderWriterLock.cs

來源:

ReaderWriterLock.cs

來源:

ReaderWriterLock.cs

來源:

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

參數

傳回

LockCookie 值。

屬性

UnsupportedOSPlatformAttribute

例外狀況

範例

以下程式碼範例說明如何請求讀取鎖、將讀取鎖定升級為寫入鎖定，以及再次降級為讀取鎖定。

此程式碼是該類別更大 ReaderWriterLock 範例的一部分。

// 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

備註

當執行緒呼叫 UpgradeToWriterLock 時，無論鎖數如何，都會釋放讀取鎖，執行緒會進入寫入鎖的隊列末端。 因此，其他執行緒可能會在請求升級的執行緒獲得寫入鎖定之前，先寫入該資源。

要恢復鎖定狀態，請 DowngradeFromWriterLock 使用 LockCookie return by UpgradeToWriterLock呼叫。 請勿將此 LockCookie 用於 RestoreLock。

當執行緒沒有讀取鎖定時，請勿使用 UpgradeToWriterLock。 請改用 AcquireWriterLock。

關於有效的逾時值，請參見 ReaderWriterLock。

另請參閱

• 管理的執行緒
• ReaderWriterLock

來源:

ReaderWriterLock.cs

來源:

ReaderWriterLock.cs

來源:

ReaderWriterLock.cs

來源:

ReaderWriterLock.cs

來源:

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

參數

傳回

LockCookie 值。

屬性

UnsupportedOSPlatformAttribute

例外狀況

備註

當執行緒呼叫 UpgradeToWriterLock 時，無論鎖數如何，都會釋放讀取鎖，執行緒會進入寫入鎖的隊列末端。 因此，其他執行緒可能會在請求升級的執行緒獲得寫入鎖定之前，先寫入該資源。

要恢復鎖定狀態，請 DowngradeFromWriterLock 使用 LockCookie return by UpgradeToWriterLock呼叫。 請勿將此 LockCookie 用於 RestoreLock。

當執行緒沒有讀取鎖定時，請勿使用 UpgradeToWriterLock。 請改用 AcquireWriterLock。

關於有效的逾時值，請參見 ReaderWriterLock。

另請參閱

• 管理的執行緒
• ReaderWriterLock