互斥锁类很容易被误解，而全局互斥锁更是如此。
在创建全局互斥对象时使用什么是好的、安全的模式?
一个会起作用的
不管我的机器在什么地方 是否保证正确释放互斥锁 如果没有获取互斥锁，则可选地不会永远挂起 处理其他进程放弃互斥锁的情况
当前回答
我想要确保这是存在的，因为它很难做到正确:
using System.Runtime.InteropServices; //GuidAttribute
using System.Reflection; //Assembly
using System.Threading; //Mutex
using System.Security.AccessControl; //MutexAccessRule
using System.Security.Principal; //SecurityIdentifier
static void Main(string[] args)
{
// get application GUID as defined in AssemblyInfo.cs
string appGuid =
((GuidAttribute)Assembly.GetExecutingAssembly().
GetCustomAttributes(typeof(GuidAttribute), false).
GetValue(0)).Value.ToString();
// unique id for global mutex - Global prefix means it is global to the machine
string mutexId = string.Format( "Global\\{{{0}}}", appGuid );
// Need a place to store a return value in Mutex() constructor call
bool createdNew;
// edited by Jeremy Wiebe to add example of setting up security for multi-user usage
// edited by 'Marc' to work also on localized systems (don't use just "Everyone")
var allowEveryoneRule =
new MutexAccessRule( new SecurityIdentifier( WellKnownSidType.WorldSid
, null)
, MutexRights.FullControl
, AccessControlType.Allow
);
var securitySettings = new MutexSecurity();
securitySettings.AddAccessRule(allowEveryoneRule);
// edited by MasonGZhwiti to prevent race condition on security settings via VanNguyen
using (var mutex = new Mutex(false, mutexId, out createdNew, securitySettings))
{
// edited by acidzombie24
var hasHandle = false;
try
{
try
{
// note, you may want to time out here instead of waiting forever
// edited by acidzombie24
// mutex.WaitOne(Timeout.Infinite, false);
hasHandle = mutex.WaitOne(5000, false);
if (hasHandle == false)
throw new TimeoutException("Timeout waiting for exclusive access");
}
catch (AbandonedMutexException)
{
// Log the fact that the mutex was abandoned in another process,
// it will still get acquired
hasHandle = true;
}
// Perform your work here.
}
finally
{
// edited by acidzombie24, added if statement
if(hasHandle)
mutex.ReleaseMutex();
}
}
}
其他回答
一个全局互斥锁不仅仅是为了确保一个应用程序只有一个实例。我个人更喜欢用微软。创建一个单实例WPF应用程序的正确方法是什么?(Dale Ragan回答)……我发现，将新应用程序启动时接收到的参数传递给初始的单实例应用程序更容易。
但是关于这个线程中之前的一些代码，我宁愿不每次我想对它有一个锁时都创建一个互斥锁。对于单实例应用程序来说，这可能没问题，但在其他用途中，我认为这有点过头了。
这就是为什么我建议这样实现:
用法:
static MutexGlobal _globalMutex = null;
static MutexGlobal GlobalMutexAccessEMTP
{
get
{
if (_globalMutex == null)
{
_globalMutex = new MutexGlobal();
}
return _globalMutex;
}
}
using (GlobalMutexAccessEMTP.GetAwaiter())
{
...
}
互斥锁全局包装器:
using System;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Security.AccessControl;
using System.Security.Principal;
using System.Threading;
namespace HQ.Util.General.Threading
{
public class MutexGlobal : IDisposable
{
// ************************************************************************
public string Name { get; private set; }
internal Mutex Mutex { get; private set; }
public int DefaultTimeOut { get; set; }
public Func<int, bool> FuncTimeOutRetry { get; set; }
// ************************************************************************
public static MutexGlobal GetApplicationMutex(int defaultTimeOut = Timeout.Infinite)
{
return new MutexGlobal(defaultTimeOut, ((GuidAttribute)Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(GuidAttribute), false).GetValue(0)).Value);
}
// ************************************************************************
public MutexGlobal(int defaultTimeOut = Timeout.Infinite, string specificName = null)
{
try
{
if (string.IsNullOrEmpty(specificName))
{
Name = Guid.NewGuid().ToString();
}
else
{
Name = specificName;
}
Name = string.Format("Global\\{{{0}}}", Name);
DefaultTimeOut = defaultTimeOut;
FuncTimeOutRetry = DefaultFuncTimeOutRetry;
var allowEveryoneRule = new MutexAccessRule(new SecurityIdentifier(WellKnownSidType.WorldSid, null), MutexRights.FullControl, AccessControlType.Allow);
var securitySettings = new MutexSecurity();
securitySettings.AddAccessRule(allowEveryoneRule);
Mutex = new Mutex(false, Name, out bool createdNew, securitySettings);
if (Mutex == null)
{
throw new Exception($"Unable to create mutex: {Name}");
}
}
catch (Exception ex)
{
Log.Log.Instance.AddEntry(Log.LogType.LogException, $"Unable to create Mutex: {Name}", ex);
throw;
}
}
// ************************************************************************
/// <summary>
///
/// </summary>
/// <param name="timeOut"></param>
/// <returns></returns>
public MutexGlobalAwaiter GetAwaiter(int timeOut)
{
return new MutexGlobalAwaiter(this, timeOut);
}
// ************************************************************************
/// <summary>
///
/// </summary>
/// <param name="timeOut"></param>
/// <returns></returns>
public MutexGlobalAwaiter GetAwaiter()
{
return new MutexGlobalAwaiter(this, DefaultTimeOut);
}
// ************************************************************************
/// <summary>
/// This method could either throw any user specific exception or return
/// true to retry. Otherwise, retruning false will let the thread continue
/// and you should verify the state of MutexGlobalAwaiter.HasTimedOut to
/// take proper action depending on timeout or not.
/// </summary>
/// <param name="timeOutUsed"></param>
/// <returns></returns>
private bool DefaultFuncTimeOutRetry(int timeOutUsed)
{
// throw new TimeoutException($"Mutex {Name} timed out {timeOutUsed}.");
Log.Log.Instance.AddEntry(Log.LogType.LogWarning, $"Mutex {Name} timeout: {timeOutUsed}.");
return true; // retry
}
// ************************************************************************
public void Dispose()
{
if (Mutex != null)
{
Mutex.ReleaseMutex();
Mutex.Close();
}
}
// ************************************************************************
}
}
等待
using System;
namespace HQ.Util.General.Threading
{
public class MutexGlobalAwaiter : IDisposable
{
MutexGlobal _mutexGlobal = null;
public bool HasTimedOut { get; set; } = false;
internal MutexGlobalAwaiter(MutexGlobal mutexEx, int timeOut)
{
_mutexGlobal = mutexEx;
do
{
HasTimedOut = !_mutexGlobal.Mutex.WaitOne(timeOut, false);
if (! HasTimedOut) // Signal received
{
return;
}
} while (_mutexGlobal.FuncTimeOutRetry(timeOut));
}
#region IDisposable Support
private bool disposedValue = false; // To detect redundant calls
protected virtual void Dispose(bool disposing)
{
if (!disposedValue)
{
if (disposing)
{
_mutexGlobal.Mutex.ReleaseMutex();
}
// TODO: free unmanaged resources (unmanaged objects) and override a finalizer below.
// TODO: set large fields to null.
disposedValue = true;
}
}
// TODO: override a finalizer only if Dispose(bool disposing) above has code to free unmanaged resources.
// ~MutexExAwaiter()
// {
// // Do not change this code. Put cleanup code in Dispose(bool disposing) above.
// Dispose(false);
// }
// This code added to correctly implement the disposable pattern.
public void Dispose()
{
// Do not change this code. Put cleanup code in Dispose(bool disposing) above.
Dispose(true);
// TODO: uncomment the following line if the finalizer is overridden above.
// GC.SuppressFinalize(this);
}
#endregion
}
}
一个没有WaitOne的解决方案，因为它会导致一个AbandonedMutexException。 这个解决方案使用互斥量构造函数返回createdNew布尔值来检查互斥量是否已经创建。它还使用GetType()。GUID，因此重命名一个可执行文件不允许多个实例。
全局互斥与局部互斥参见: https://learn.microsoft.com/en-us/dotnet/api/system.threading.mutex?view=netframework-4.8
private Mutex mutex;
private bool mutexCreated;
public App()
{
string mutexId = $"Global\\{GetType().GUID}";
mutex = new Mutex(true, mutexId, out mutexCreated);
}
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
if (!mutexCreated)
{
MessageBox.Show("Already started!");
Shutdown();
}
}
因为互斥锁实现了IDisposable，所以它被自动释放，但是为了完整性，调用dispose:
protected override void OnExit(ExitEventArgs e)
{
base.OnExit(e);
mutex.Dispose();
}
将所有内容移动到基类中，并从接受的答案中添加allowEveryoneRule。还添加了ReleaseMutex，虽然它看起来不像真的需要，因为它是由操作系统自动释放的(如果应用程序崩溃了，你需要重新启动ReleaseMutex吗?)
public class SingleApplication : Application
{
private Mutex mutex;
private bool mutexCreated;
public SingleApplication()
{
string mutexId = $"Global\\{GetType().GUID}";
MutexAccessRule allowEveryoneRule = new MutexAccessRule(
new SecurityIdentifier(WellKnownSidType.WorldSid, null),
MutexRights.FullControl,
AccessControlType.Allow);
MutexSecurity securitySettings = new MutexSecurity();
securitySettings.AddAccessRule(allowEveryoneRule);
// initiallyOwned: true == false + mutex.WaitOne()
mutex = new Mutex(initiallyOwned: true, mutexId, out mutexCreated, securitySettings);
}
protected override void OnExit(ExitEventArgs e)
{
base.OnExit(e);
if (mutexCreated)
{
try
{
mutex.ReleaseMutex();
}
catch (ApplicationException ex)
{
MessageBox.Show(ex.Message, ex.GetType().FullName, MessageBoxButton.OK, MessageBoxImage.Error);
}
}
mutex.Dispose();
}
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
if (!mutexCreated)
{
MessageBox.Show("Already started!");
Shutdown();
}
}
}
如果另一个实例已经在运行，则此示例将在5秒后退出。
// unique id for global mutex - Global prefix means it is global to the machine
const string mutex_id = "Global\\{B1E7934A-F688-417f-8FCB-65C3985E9E27}";
static void Main(string[] args)
{
using (var mutex = new Mutex(false, mutex_id))
{
try
{
try
{
if (!mutex.WaitOne(TimeSpan.FromSeconds(5), false))
{
Console.WriteLine("Another instance of this program is running");
Environment.Exit(0);
}
}
catch (AbandonedMutexException)
{
// Log the fact the mutex was abandoned in another process, it will still get aquired
}
// Perform your work here.
}
finally
{
mutex.ReleaseMutex();
}
}
}
Mutex和WinApi CreateMutex()都不适合我。
另一种解决方案:
static class Program
{
[STAThread]
static void Main()
{
if (SingleApplicationDetector.IsRunning()) {
return;
}
Application.Run(new MainForm());
SingleApplicationDetector.Close();
}
}
和SingleApplicationDetector:
using System;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Security.AccessControl;
using System.Threading;
public static class SingleApplicationDetector
{
public static bool IsRunning()
{
string guid = ((GuidAttribute)Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(GuidAttribute), false).GetValue(0)).Value.ToString();
var semaphoreName = @"Global\" + guid;
try {
__semaphore = Semaphore.OpenExisting(semaphoreName, SemaphoreRights.Synchronize);
Close();
return true;
}
catch (Exception ex) {
__semaphore = new Semaphore(0, 1, semaphoreName);
return false;
}
}
public static void Close()
{
if (__semaphore != null) {
__semaphore.Close();
__semaphore = null;
}
}
private static Semaphore __semaphore;
}
使用信号量而不是互斥锁的原因:
Mutex类强制线程标识，因此只有获得互斥锁的线程才能释放它。相反，Semaphore类并不强制执行线程标识。 < < System.Threading.Mutex
裁判:Semaphore.OpenExisting ()
我想要确保这是存在的，因为它很难做到正确:
using System.Runtime.InteropServices; //GuidAttribute
using System.Reflection; //Assembly
using System.Threading; //Mutex
using System.Security.AccessControl; //MutexAccessRule
using System.Security.Principal; //SecurityIdentifier
static void Main(string[] args)
{
// get application GUID as defined in AssemblyInfo.cs
string appGuid =
((GuidAttribute)Assembly.GetExecutingAssembly().
GetCustomAttributes(typeof(GuidAttribute), false).
GetValue(0)).Value.ToString();
// unique id for global mutex - Global prefix means it is global to the machine
string mutexId = string.Format( "Global\\{{{0}}}", appGuid );
// Need a place to store a return value in Mutex() constructor call
bool createdNew;
// edited by Jeremy Wiebe to add example of setting up security for multi-user usage
// edited by 'Marc' to work also on localized systems (don't use just "Everyone")
var allowEveryoneRule =
new MutexAccessRule( new SecurityIdentifier( WellKnownSidType.WorldSid
, null)
, MutexRights.FullControl
, AccessControlType.Allow
);
var securitySettings = new MutexSecurity();
securitySettings.AddAccessRule(allowEveryoneRule);
// edited by MasonGZhwiti to prevent race condition on security settings via VanNguyen
using (var mutex = new Mutex(false, mutexId, out createdNew, securitySettings))
{
// edited by acidzombie24
var hasHandle = false;
try
{
try
{
// note, you may want to time out here instead of waiting forever
// edited by acidzombie24
// mutex.WaitOne(Timeout.Infinite, false);
hasHandle = mutex.WaitOne(5000, false);
if (hasHandle == false)
throw new TimeoutException("Timeout waiting for exclusive access");
}
catch (AbandonedMutexException)
{
// Log the fact that the mutex was abandoned in another process,
// it will still get acquired
hasHandle = true;
}
// Perform your work here.
}
finally
{
// edited by acidzombie24, added if statement
if(hasHandle)
mutex.ReleaseMutex();
}
}
}
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