Interlocked クラスとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

Interlocked クラス

複数のスレッドで共有される変数に分割不可能な操作を提供します。

名前空間: System.Threading
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public NotInheritable Class
 Interlocked

Visual Basic (使用法)

静的クラスのメンバは、クラスのインスタンスなしに直接アクセスされます。

public static class Interlocked

C++

public ref class Interlocked abstract sealed

public final class Interlocked

JScript

public final class Interlocked

解説

このクラスのメソッドは、他のスレッドからアクセスできる変数をスレッドが更新しているとき、または 2 つのスレッドが別々のプロセッサで同時に実行されているときに、スケジューラがコンテキストの切り替えを行うと発生するエラーを防ぎます。このクラスのメンバは、例外をスローしません。

Increment メソッドと Decrement メソッドは、1 回の操作で変数をインクリメントまたはデクリメントして、結果値を格納します。変数のインクリメントは、ほとんどのコンピュータでは、分割不可能な操作ではなく、次のような手順が必要となります。

Increment と Decrement を使用しない場合は、最初の 2 つの手順を実行した後で、別のスレッドが優先処理される可能性があります。また、別のスレッドが 3 つのすべての手順を先行して完了させることもあります。最初のスレッドが実行を再開したときにインスタンス変数の値が上書きされるため、2 番目のスレッドが実行したインクリメントまたはデクリメントの結果は失われます。

Exchange メソッドは、指定した変数の値を分割不可能な方法で交換します。CompareExchange メソッドは、2 つの操作を組み合わせます。ここでは、2 つの値を比較し、その比較結果に基づいてその変数のいずれかに 3 つ目の値を格納します。比較操作および交換操作は、分割不可能な操作として実行されます。

使用例

スレッドセーフなリソースロック機構の例を次に示します。

Visual Basic

Imports System
Imports System.Threading

Namespace InterlockedExchange_Example
    Class MyInterlockedExchangeExampleClass
        '0 for false, 1 for true.
        Private Shared usingResource As
 Integer = 0

        Private Shared currentMso As
 [Object]
        Private Shared globalMso As
 New [Object]()
        Private Const numThreadIterations As
 Integer = 5
        Private Const numThreads As
 Integer = 10

        <MTAThread> _
        Shared Sub Main()
            Dim myThread As Thread
            Dim rnd As New
 Random()

            Dim i As Integer
            For i = 0 To numThreads - 1
                myThread = New Thread(AddressOf
 MyThreadProc)
                myThread.Name = [String].Format("Thread{0}",
 i + 1)

                'Wait a random amount of time before starting next thread.
                Thread.Sleep(rnd.Next(0, 1000))
                myThread.Start()
            Next i
        End Sub 'Main

        Private Shared Sub
 MyThreadProc()
            Dim i As Integer
            For i = 0 To numThreadIterations
 - 1
                UseResource()

                'Wait 1 second before next attempt.
                Thread.Sleep(1000)
            Next i
        End Sub 'MyThreadProc

        'A simple method that denies reentrancy.
        Shared Function UseResource() As
 Boolean
            '0 indicates that the method is not in use.
            If 0 = Interlocked.Exchange(usingResource, 1) Then
                Console.WriteLine("{0} acquired the lock",
 Thread.CurrentThread.Name)

                'Code to access a resource that is not thread safe would
 go here.
                'Simulate some work
                Thread.Sleep(500)

                Console.WriteLine("{0} exiting lock",
 Thread.CurrentThread.Name)

                'Release the lock
                Interlocked.Exchange(usingResource, 0)
                Return True
            Else
                Console.WriteLine("   {0} was denied the lock",
 Thread.CurrentThread.Name)
                Return False
            End If
        End Function 'UseResource
    End Class 'MyInterlockedExchangeExampleClass
 
End Namespace 'InterlockedExchange_Example

using System;
using System.Threading;

namespace InterlockedExchange_Example
{
    class MyInterlockedExchangeExampleClass
    {
        //0 for false, 1 for true.
        private static int
 usingResource = 0;

        private static Object currentMso;
        private static Object globalMso = new
 Object();
        private const int
 numThreadIterations = 5;
        private const int
 numThreads = 10;

        static void Main()
        {
            Thread myThread;
            Random rnd = new Random();

            for(int i = 0; i < numThreads;
 i++)
            {
                myThread = new Thread(new ThreadStart(MyThreadProc));
                myThread.Name = String.Format("Thread{0}", i + 1);
            
                //Wait a random amount of time before starting next
 thread.
                Thread.Sleep(rnd.Next(0, 1000));
                myThread.Start();
            }
        }

        private static void
 MyThreadProc()
        {
            for(int i = 0; i < numThreadIterations;
 i++)
            {
                UseResource();
            
                //Wait 1 second before next attempt.
                Thread.Sleep(1000);
            }
        }

        //A simple method that denies reentrancy.
        static bool UseResource()
        {
            //0 indicates that the method is not in use.
            if(0 == Interlocked.Exchange(ref usingResource, 1))
            {
                Console.WriteLine("{0} acquired the lock", Thread.CurrentThread.Name);
            
                //Code to access a resource that is not thread safe
 would go here.
            
                //Simulate some work
                Thread.Sleep(500);

                Console.WriteLine("{0} exiting lock", Thread.CurrentThread.Name);
            
                //Release the lock
                Interlocked.Exchange(ref usingResource, 0);
                return true;
            }
            else
            {
                Console.WriteLine("   {0} was denied the lock", Thread.CurrentThread.Name);
                return false;
            }
        }

    }
}

C++

using namespace System;
using namespace System::Threading;
const int numThreads = 10;
const int numThreadIterations = 5;
ref class MyInterlockedExchangeExampleClass
{
public:
   static void MyThreadProc()
   {
      for ( int i = 0; i < numThreadIterations;
 i++ )
      {
         UseResource();
         
         //Wait 1 second before next attempt.
         Thread::Sleep( 1000 );

      }
   }


private:

   //A simple method that denies reentrancy.
   static bool UseResource()
   {
      
      //0 indicates that the method is not in use.
      if ( 0 == Interlocked::Exchange( usingResource, 1 ) )
      {
         Console::WriteLine( " {0} acquired the lock", Thread::CurrentThread->Name
 );
         
         //Code to access a resource that is not thread safe would go
 here.
         //Simulate some work
         Thread::Sleep( 500 );
         Console::WriteLine( " {0} exiting lock", Thread::CurrentThread->Name
 );
         
         //Release the lock
         Interlocked::Exchange( usingResource, 0 );
         return true;
      }
      else
      {
         Console::WriteLine( " {0} was denied the lock", Thread::CurrentThread->Name
 );
         return false;
      }
   }


   //0 for false, 1 for true.
   static int usingResource;
   static Object^ globalMso = gcnew Object;
};

int main()
{
   Thread^ myThread;
   Random^ rnd = gcnew Random;
   for ( int i = 0; i < numThreads; i++
 )
   {
      myThread = gcnew Thread( gcnew ThreadStart( MyInterlockedExchangeExampleClass::MyThreadProc
 ) );
      myThread->Name = String::Format( "Thread {0}", i + 1 );
      
      //Wait a random amount of time before starting next thread.
      Thread::Sleep( rnd->Next( 0, 1000 ) );
      myThread->Start();

   }
}

package InterlockedExchange_Example ; 

import System .* ;
import System.Threading .* ;
import System.Threading.Thread;

class MyInterlockedExchangeExampleClass
{
    //0 for false, 1 for true.
    private static int usingResource
 = 0;
    private static Object currentMso;
    private static Object globalMso = new
 Object();
    private static int numThreadIterations
 = 5;
    private static int numThreads
 = 10;

    public static void main(String[]
 args)
    {
        Thread myThread;
        Random rnd = new Random();

        for (int i = 0; i < numThreads;
 i++) {
            myThread = new Thread(new ThreadStart(MyThreadProc));
            myThread.set_Name(String.Format("Thread{0}",
                String.valueOf(i + 1)));

            //Wait a random amount of time before starting next thread.
            Thread.Sleep(rnd.Next(0, 1000));
            myThread.Start();
        }
    } //main

    private static void
 MyThreadProc()
    {
        for (int i = 0; i < numThreadIterations;
 i++) {
            UseResource();

            //Wait 1 second before next attempt.
            Thread.Sleep(1000);
        }
    } //MyThreadProc

    //A simple method that denies reentrancy.
    static boolean UseResource()
    {
        //0 indicates that the method is not in use.
        if (0 == Interlocked.Exchange(usingResource, 1)) {
            Console.WriteLine("{0} acquired the lock",
                Thread.get_CurrentThread().get_Name());

            //Code to access a resource that is not thread safe would go
 here.
            //Simulate some work
            Thread.Sleep(500);
            Console.WriteLine("{0} exiting lock", 
                Thread.get_CurrentThread().get_Name());

            //Release the lock
            Interlocked.Exchange(usingResource, 0);
            return true;
        }
        else {
            Console.WriteLine("   {0} was denied the lock", 
                Thread.get_CurrentThread().get_Name());
            return false;
        }
    } //UseResource
} //MyInterlockedExchangeExampleClass