ReaderWriterLock.UpgradeToWriterLock 方法

定义

命名空间:: System.Threading

程序集:: netstandard.dll, System.Threading.dll

程序集:: System.Threading.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

将读取器锁升级到编写器锁。

重载

名称	说明
UpgradeToWriterLock(Int32)	使用 Int32 超时值将读取器锁升级到写入器锁。
UpgradeToWriterLock(TimeSpan)	使用 `TimeSpan` 超时值将读取器锁升级到写入器锁。

UpgradeToWriterLock(Int32)

Source:: ReaderWriterLock.cs

Source:: ReaderWriterLock.cs

Source:: ReaderWriterLock.cs

Source:: ReaderWriterLock.cs

Source:: ReaderWriterLock.cs

使用 Int32 超时值将读取器锁升级到写入器锁。

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

参数

millisecondsTimeout: Int32

超时（以毫秒为单位）。

LockCookie

一个 LockCookie 值。

属性: UnsupportedOSPlatformAttribute

例外

ApplicationException

millisecondsTimeout 在授予锁定请求之前过期。

示例

下面的代码示例演示如何请求读取器锁、将读取器锁升级到编写器锁，以及再次降级到读取器锁。

此代码是为类提供的大型示例的 ReaderWriterLock 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

注解

当线程调用 UpgradeToWriterLock 读取器锁时，无论锁计数如何，线程都会进入写入器锁队列的末尾。因此，在向请求升级的线程授予写入器锁之前，其他线程可能会写入资源。

重要

除非调用 UpgradeToWriterLock 该方法的线程可以重新获取读取器锁，否则不会引发超时异常。如果没有其他线程等待编写器锁，则立即发生这种情况。但是，如果另一个线程排队等待编写器锁，则调用 UpgradeToWriterLock 该方法的线程在释放其锁之前无法重新获取读取器锁，并且一个线程已获取并释放编写器锁。即使请求编写器锁的另一个线程在当前线程调用 UpgradeToWriterLock 该方法后请求它，也是如此。

若要还原锁定状态，请使用LockCookie返回者UpgradeToWriterLock调用 DowngradeFromWriterLock 。请勿将此 LockCookie 与 RestoreLock..

当线程没有读取器锁时，请勿使用 UpgradeToWriterLock。请改用 AcquireWriterLock。

有关有效的超时值，请参阅 ReaderWriterLock。

另请参阅

适用于

UpgradeToWriterLock(TimeSpan)

Source:: ReaderWriterLock.cs

Source:: ReaderWriterLock.cs

Source:: ReaderWriterLock.cs

Source:: ReaderWriterLock.cs

Source:: ReaderWriterLock.cs

使用 TimeSpan 超时值将读取器锁升级到写入器锁。

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

参数

timeout: TimeSpan

TimeSpan指定超时期限。

LockCookie

一个 LockCookie 值。

属性: UnsupportedOSPlatformAttribute

例外

ApplicationException

timeout 在授予锁定请求之前过期。

ArgumentOutOfRangeException

timeout 指定除 -1 毫秒以外的负值。

注解

重要

若要还原锁定状态，请使用LockCookie返回者UpgradeToWriterLock调用 DowngradeFromWriterLock 。请勿将此 LockCookie 与 RestoreLock..

当线程没有读取器锁时，请勿使用 UpgradeToWriterLock。请改用 AcquireWriterLock。

有关有效的超时值，请参阅 ReaderWriterLock。

另请参阅

适用于

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