Mutex.ReleaseMutex 方法
定义
重要
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Mutex释放一次。
public:
void ReleaseMutex();public void ReleaseMutex();member this.ReleaseMutex : unit -> unitPublic Sub ReleaseMutex ()例外
调用线程不拥有互斥体。
当前实例已释放。
示例
以下示例演示如何使用本地 Mutex 对象来同步对受保护资源的访问。 创建互斥体的线程最初不拥有它。 此方法 ReleaseMutex 用于在不再需要互斥体时释放互斥体。
// This example shows how a Mutex is used to synchronize access
// to a protected resource. Unlike Monitor, Mutex can be used with
// WaitHandle.WaitAll and WaitAny, and can be passed across
// AppDomain boundaries.
using System;
using System.Threading;
class Test13
{
// Create a new Mutex. The creating thread does not own the
// Mutex.
private static Mutex mut = new Mutex();
private const int numIterations = 1;
private const int numThreads = 3;
static void Main()
{
// Create the threads that will use the protected resource.
for(int i = 0; i < numThreads; i++)
{
Thread myThread = new Thread(new ThreadStart(MyThreadProc));
myThread.Name = String.Format("Thread{0}", i + 1);
myThread.Start();
}
// The main thread exits, but the application continues to
// run until all foreground threads have exited.
}
private static void MyThreadProc()
{
for(int i = 0; i < numIterations; i++)
{
UseResource();
}
}
// This method represents a resource that must be synchronized
// so that only one thread at a time can enter.
private static void UseResource()
{
// Wait until it is safe to enter.
mut.WaitOne();
Console.WriteLine("{0} has entered the protected area",
Thread.CurrentThread.Name);
// Place code to access non-reentrant resources here.
// Simulate some work.
Thread.Sleep(500);
Console.WriteLine("{0} is leaving the protected area\r\n",
Thread.CurrentThread.Name);
// Release the Mutex.
mut.ReleaseMutex();
}
}
' This example shows how a Mutex is used to synchronize access
' to a protected resource. Unlike Monitor, Mutex can be used with
' WaitHandle.WaitAll and WaitAny, and can be passed across
' AppDomain boundaries.
Imports System.Threading
Class Test
' Create a new Mutex. The creating thread does not own the
' Mutex.
Private Shared mut As New Mutex()
Private Const numIterations As Integer = 1
Private Const numThreads As Integer = 3
<MTAThread> _
Shared Sub Main()
' Create the threads that will use the protected resource.
Dim i As Integer
For i = 1 To numThreads
Dim myThread As New Thread(AddressOf MyThreadProc)
myThread.Name = [String].Format("Thread{0}", i)
myThread.Start()
Next i
' The main thread exits, but the application continues to
' run until all foreground threads have exited.
End Sub
Private Shared Sub MyThreadProc()
Dim i As Integer
For i = 1 To numIterations
UseResource()
Next i
End Sub
' This method represents a resource that must be synchronized
' so that only one thread at a time can enter.
Private Shared Sub UseResource()
' Wait until it is safe to enter.
mut.WaitOne()
Console.WriteLine("{0} has entered protected area", _
Thread.CurrentThread.Name)
' Place code to access non-reentrant resources here.
' Simulate some work
Thread.Sleep(500)
Console.WriteLine("{0} is leaving protected area" & vbCrLf, _
Thread.CurrentThread.Name)
' Release Mutex.
mut.ReleaseMutex()
End Sub
End Class
注解
每当线程获取互斥体（例如，通过调用其 WaitOne 方法），它随后必须调用 ReleaseMutex 以放弃互斥体所有权，并取消阻止试图获取互斥体所有权的其他线程。 如果尝试获取互斥锁的所有权失败（例如，当对方法WaitOnemillisecondsTimeout的调用timeout因请求超时而返回false时），则线程不应调用ReleaseMutex，在这种情况下，也不允许线程访问受互斥体保护的资源，如以下示例所示。
using System;
using System.Threading;
class Example
{
// Create a new Mutex. The creating thread does not own the mutex.
private static Mutex mut = new Mutex();
private const int numIterations = 1;
private const int numThreads = 3;
static void Main()
{
Example ex = new Example();
ex.StartThreads();
}
private void StartThreads()
{
// Create the threads that will use the protected resource.
for(int i = 0; i < numThreads; i++)
{
Thread newThread = new Thread(new ThreadStart(ThreadProc));
newThread.Name = String.Format("Thread{0}", i + 1);
newThread.Start();
}
// The main thread returns to Main and exits, but the application continues to
// run until all foreground threads have exited.
}
private static void ThreadProc()
{
for(int i = 0; i < numIterations; i++)
{
UseResource();
}
}
// This method represents a resource that must be synchronized
// so that only one thread at a time can enter.
private static void UseResource()
{
// Wait until it is safe to enter, and do not enter if the request times out.
Console.WriteLine("{0} is requesting the mutex", Thread.CurrentThread.Name);
if (mut.WaitOne(1000)) {
Console.WriteLine("{0} has entered the protected area",
Thread.CurrentThread.Name);
// Place code to access non-reentrant resources here.
// Simulate some work.
Thread.Sleep(5000);
Console.WriteLine("{0} is leaving the protected area",
Thread.CurrentThread.Name);
// Release the Mutex.
mut.ReleaseMutex();
Console.WriteLine("{0} has released the mutex",
Thread.CurrentThread.Name);
}
else {
Console.WriteLine("{0} will not acquire the mutex",
Thread.CurrentThread.Name);
}
}
~Example()
{
mut.Dispose();
}
}
// The example displays output like the following:
// Thread1 is requesting the mutex
// Thread1 has entered the protected area
// Thread2 is requesting the mutex
// Thread3 is requesting the mutex
// Thread2 will not acquire the mutex
// Thread3 will not acquire the mutex
// Thread1 is leaving the protected area
// Thread1 has released the mutex
Imports System.Threading
Class Example
' Create a new Mutex. The creating thread does not own the mutex.
Private mut As New Mutex()
Private Const numIterations As Integer = 1
Private Const numThreads As Integer = 3
Public Shared Sub Main()
Dim ex As New Example()
ex.StartThreads()
End Sub
Private Sub StartThreads()
' Create the threads that will use the protected resource.
For i As Integer = 0 To numThreads - 1
Dim newThread As New Thread(AddressOf ThreadProc)
newThread.Name = String.Format("Thread{0}", i + 1)
newThread.Start()
Next
' The main thread returns to Main and exits, but the application continues to
' run until all foreground threads have exited.
End Sub
Private Sub ThreadProc()
For i As Integer = 0 To numIterations - 1
UseResource()
Next
End Sub
' This method represents a resource that must be synchronized
' so that only one thread at a time can enter.
Private Sub UseResource()
' Wait until it is safe to enter.
Console.WriteLine("{0} is requesting the mutex",
Thread.CurrentThread.Name)
If mut.WaitOne(1000) Then
Console.WriteLine("{0} has entered the protected area",
Thread.CurrentThread.Name)
' Place code to access non-reentrant resources here.
' Simulate some work.
Thread.Sleep(5000)
Console.WriteLine("{0} is leaving the protected area",
Thread.CurrentThread.Name)
' Release the Mutex.
mut.ReleaseMutex()
Console.WriteLine("{0} has released the mutex",
Thread.CurrentThread.Name)
Else
Console.WriteLine("{0} will not acquire the mutex",
Thread.CurrentThread.Name)
End If
End Sub
Protected Overrides Sub Finalize()
mut.Dispose()
End Sub
End Class
' The example displays output like the following:
' Thread1 is requesting the mutex
' Thread1 has entered the protected area
' Thread2 is requesting the mutex
' Thread3 is requesting the mutex
' Thread2 will not acquire the mutex
' Thread3 will not acquire the mutex
' Thread1 is leaving the protected area
' Thread1 has released the mutex
拥有互斥体的线程可以在重复的等待函数调用中指定相同的互斥体，而不会阻止其执行。 公共语言运行时保留调用数。 线程必须调用 ReleaseMutex 相同的次数才能释放互斥体的所有权。
如果线程在拥有互斥体时终止，则表示将放弃互斥体。 互斥体的状态设置为信号，下一个等待线程获取所有权。 如果没有人拥有互斥体，则表示互斥体的状态。 从 .NET Framework 版本 2.0 开始，AbandonedMutexException会在获取互斥体的下一个线程中引发。 在 .NET Framework 版本 2.0 之前，不会引发异常。
注意
放弃的互斥体通常表示代码中出现严重错误。 当线程退出而不释放互斥体时，受互斥体保护的数据结构可能不处于一致状态。 如果可以验证数据结构的完整性，则请求互斥体所有权的下一个线程可以处理此异常并继续。
对于系统范围的 mutex，放弃的 mutex 可能指示应用程序已突然终止（例如，通过使用 Windows 任务管理器终止）。
