ReaderWriterLock.WriterSeqNum 속성
정의
중요
일부 정보는 릴리스되기 전에 상당 부분 수정될 수 있는 시험판 제품과 관련이 있습니다. Microsoft는 여기에 제공된 정보에 대해 어떠한 명시적이거나 묵시적인 보증도 하지 않습니다.
현재 시퀀스 번호를 가져옵니다.
public:
property int WriterSeqNum { int get(); };public int WriterSeqNum { get; }member this.WriterSeqNum : intPublic ReadOnly Property WriterSeqNum As Integer속성 값
현재 시퀀스 번호입니다.
예제
다음 코드 예제에서는 현재 스레드가 마지막으로 기록기 잠금을 유지한 이후 다른 스레드가 보호된 리소스에 대한 기록기 잠금을 획득했는지 여부를 확인하기 위해 속성 및 AnyWritersSince 메서드를 사용하는 WriterSeqNum 방법을 보여줍니다.
이 코드는 클래스에 제공된 더 큰 예제의 ReaderWriterLock 일부입니다.
// 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
스레드가 기록기 잠금을 획득할 때마다 시퀀스 번호가 증가합니다. 다른 스레드가 그 동안 기록기 AnyWritersSince 잠금을 획득했는지 여부를 확인하려면 시퀀스 번호를 저장하고 나중에 전달할 수 있습니다.
사용할 수 있습니다 WriterSeqNum 애플리케이션 성능을 향상 시키기 위해. 예를 들어 스레드는 판독기 잠금을 유지하면서 얻은 정보를 캐시할 수 있습니다. 잠금을 해제한 후 나중에 잠금을 다시 확인한 후 스레드는 다른 스레드가 호출 AnyWritersSince하여 리소스에 기록되었는지 여부를 확인할 수 있습니다. 그렇지 않은 경우 캐시된 정보를 사용할 수 있습니다. 이 기술은 잠금으로 보호되는 정보를 읽는 데 비용이 많이 드는 경우에 유용합니다. 예를 들어 데이터베이스 쿼리를 실행합니다.
시퀀스 번호가 유용하려면 호출자가 판독기 잠금 또는 기록기 잠금을 보유하고 있어야 합니다.