ReaderWriterLock.UpgradeToWriterLock メソッド

ソース:

ReaderWriterLock.cs

ソース:

ReaderWriterLock.cs

ソース:

ReaderWriterLock.cs

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

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

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

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

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

Public Function UpgradeToWriterLock (millisecondsTimeout As Integer) As LockCookie

パラメーター

戻り値

LockCookie 値。

属性

UnsupportedOSPlatformAttribute

例外

例

次のコード例は、リーダー ロックを要求し、リーダー ロックをライター ロックにアップグレードし、リーダー ロックに再度ダウングレードする方法を示しています。

このコードは、 クラスに対して提供されるより大きな例の ReaderWriterLock 一部です。

// 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 request a reader lock, upgrade the
// reader lock to the writer lock, and downgrade to a
// reader lock again.
static void UpgradeDowngrade( Random^ rnd, 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 );
   }

}

// 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

注釈

スレッドが呼び出 UpgradeToWriterLock すと、ロック数に関係なくリーダー ロックが解放され、スレッドはライター ロックのキューの末尾に移動します。 したがって、アップグレードを要求したスレッドにライター ロックが付与される前に、他のスレッドがリソースに書き込む可能性があります。

ロック状態を復元するには、 によってUpgradeToWriterLock返される を使用して をLockCookie呼び出しますDowngradeFromWriterLock。 これを LockCookie と共に RestoreLock使用しないでください。

スレッドにリーダー ロックがない場合は、 を使用 UpgradeToWriterLockしないでください。 代わりに、AcquireWriterLock を使用してください。

有効なタイムアウト値については、「」を参照してください ReaderWriterLock。

こちらもご覧ください

• マネージド スレッド処理
• ReaderWriterLock

ソース:

ReaderWriterLock.cs

ソース:

ReaderWriterLock.cs

ソース:

ReaderWriterLock.cs

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

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

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

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

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

Public Function UpgradeToWriterLock (timeout As TimeSpan) As LockCookie

パラメーター

戻り値

LockCookie 値。

属性

UnsupportedOSPlatformAttribute

例外

注釈

スレッドが呼び出 UpgradeToWriterLock すと、ロック数に関係なくリーダー ロックが解放され、スレッドはライター ロックのキューの末尾に移動します。 したがって、アップグレードを要求したスレッドにライター ロックが付与される前に、他のスレッドがリソースに書き込む可能性があります。

ロック状態を復元するには、 によってUpgradeToWriterLock返される を使用して をLockCookie呼び出しますDowngradeFromWriterLock。 これを LockCookie と共に RestoreLock使用しないでください。

スレッドにリーダー ロックがない場合は、 を使用 UpgradeToWriterLockしないでください。 代わりに、AcquireWriterLock を使用してください。

有効なタイムアウト値については、「」を参照してください ReaderWriterLock。

こちらもご覧ください

• マネージド スレッド処理
• ReaderWriterLock