Replaced Mutex code with a from Dapplo.Addons class written for Greenshot 1.3 "ResourceMutex", this should fix a few start-up issues.

Greenshot/Forms/MainForm.cs

@@ -26,8 +26,6 @@ using System.Diagnostics;
 using System.Drawing;
 using System.IO;
 using System.Reflection;
-using System.Security.AccessControl;
-using System.Security.Principal;
 using System.Text;
 using System.Threading;
 using System.Windows.Forms;
@@ -52,7 +50,7 @@ namespace Greenshot {
 	/// </summary>
 	public partial class MainForm : BaseForm {
 		private static ILog LOG;
-		private static Mutex _applicationMutex;
+		private static ResourceMutex _applicationMutex;
 		private static CoreConfiguration _conf;
 		public static string LogFileLocation = null;
 
@@ -82,38 +80,9 @@ namespace Greenshot {
 			try {
 				// Fix for Bug 2495900, Multi-user Environment
 				// check whether there's an local instance running already
-				
-				try {
-					// Added Mutex Security, hopefully this prevents the UnauthorizedAccessException more gracefully
-					// See an example in Bug #3131534
-					SecurityIdentifier sid = new SecurityIdentifier(WellKnownSidType.WorldSid, null);
-					MutexSecurity mutexsecurity = new MutexSecurity();
-					mutexsecurity.AddAccessRule(new MutexAccessRule(sid, MutexRights.FullControl, AccessControlType.Allow));
-					mutexsecurity.AddAccessRule(new MutexAccessRule(sid, MutexRights.ChangePermissions, AccessControlType.Deny));
-					mutexsecurity.AddAccessRule(new MutexAccessRule(sid, MutexRights.Delete, AccessControlType.Deny));
+				_applicationMutex = ResourceMutex.Create("F48E86D3-E34C-4DB7-8F8F-9A0EA55F0D08", "Greenshot", false);
 
-					bool created;
-					// 1) Create Mutex
-					_applicationMutex = new Mutex(false, @"Local\F48E86D3-E34C-4DB7-8F8F-9A0EA55F0D08", out created, mutexsecurity);
-					// 2) Get the right to it, this returns false if it's already locked
-					if (!_applicationMutex.WaitOne(0, false)) {
-						LOG.Debug("Greenshot seems already to be running!");
-						isAlreadyRunning = true;
-						// Clean up
-						_applicationMutex.Close();
-						_applicationMutex = null;
-					}
-				} catch (AbandonedMutexException e) {
-					// Another Greenshot instance didn't cleanup correctly!
-					// we can ignore the exception, it happend on the "waitone" but still the mutex belongs to us
-					LOG.Warn("Greenshot didn't cleanup correctly!", e);
-				} catch (UnauthorizedAccessException e) {
-					LOG.Warn("Greenshot is most likely already running for a different user in the same session, can't create mutex due to error: ", e);
-					isAlreadyRunning = true;
-				} catch (Exception e) {
-					LOG.Warn("Problem obtaining the Mutex, assuming it was already taken!", e);
-					isAlreadyRunning = true;
-				}
+				isAlreadyRunning = !_applicationMutex.IsLocked;
 
 				if (args.Length > 0 && LOG.IsDebugEnabled) {
 					StringBuilder argumentString = new StringBuilder();
@@ -316,7 +285,7 @@ namespace Greenshot {
 			// Remove the application mutex
 			if (_applicationMutex != null) {
 				try {
-					_applicationMutex.ReleaseMutex();
+					_applicationMutex.Dispose();
 					_applicationMutex = null;
 				} catch (Exception ex) {
 					LOG.Error("Error releasing Mutex!", ex);

Greenshot/Greenshot.csproj

@@ -212,6 +212,7 @@
     <Compile Include="Helpers\IECaptureHelper.cs" />
     <Compile Include="Helpers\IEInterop\IEContainer.cs" />
     <Compile Include="Helpers\ProcessorHelper.cs" />
+    <Compile Include="Helpers\ResourceMutex.cs" />
     <Compile Include="Help\HelpFileLoader.cs" />
     <Compile Include="Processors\TitleFixProcessor.cs" />
     <Compile Include="Helpers\WindowWrapper.cs" />

Greenshot/Helpers/ResourceMutex.cs

@@ -0,0 +1,195 @@
+/*
+	Dapplo - building blocks for desktop applications
+	Copyright (C) 2015-2016 Dapplo
+
+	For more information see: http://dapplo.net/
+	Dapplo repositories are hosted on GitHub: https://github.com/dapplo
+
+	This file is part of Dapplo.Addons
+
+	Dapplo.Addons is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	Dapplo.Addons is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Dapplo.Addons. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+using log4net;
+using System;
+using System.Security.AccessControl;
+using System.Security.Principal;
+using System.Threading;
+
+namespace Greenshot.Helpers
+{
+	/// <summary>
+	/// This comes from Dapplo.Addons, which was created for Greenshot, this file is copied here as this is the only part we use in 1.2.8
+	/// This protects your resources or application from running more than once
+	/// Simplifies the usage of the Mutex class, as described here: https://msdn.microsoft.com/en-us/library/System.Threading.Mutex.aspx
+	/// </summary>
+	public class ResourceMutex : IDisposable
+	{
+		private static ILog LOG = LogManager.GetLogger(typeof(DestinationHelper));
+		private readonly string _mutexId;
+		private readonly string _resourceName;
+		private Mutex _applicationMutex;
+
+		/// <summary>
+		/// Test if the Mutex was created and locked.
+		/// </summary>
+		public bool IsLocked
+		{
+			get;
+			set;
+		}
+
+		/// <summary>
+		/// Private constructor 
+		/// </summary>
+		/// <param name="mutexId"></param>
+		/// <param name="resourceName"></param>
+		private ResourceMutex(string mutexId, string resourceName = null)
+		{
+			_mutexId = mutexId;
+			_resourceName = resourceName ?? "some resource";
+		}
+
+		/// <summary>
+		/// Create a ResourceMutex for the specified mutex id and resource-name
+		/// </summary>
+		/// <param name="mutexId">ID of the mutex, preferably a Guid as string</param>
+		/// <param name="resourceName">Name of the resource to lock, e.g your application name, usefull for logs</param>
+		/// <param name="global">true to have a global mutex see: https://msdn.microsoft.com/en-us/library/bwe34f1k.aspx </param>
+		public static ResourceMutex Create(string mutexId, string resourceName = null, bool global = false)
+		{
+			var applicationMutex = new ResourceMutex((global ? @"Global\" : @"Local\") + mutexId, resourceName);
+			applicationMutex.Lock();
+			return applicationMutex;
+		}
+
+		/// <summary>
+		/// This tries to get the Mutex, which takes care of having multiple instances running
+		/// </summary>
+		/// <returns>true if it worked, false if another instance is already running or something went wrong</returns>
+		public bool Lock()
+		{
+			LOG.DebugFormat("{0} is trying to get Mutex {1}", _resourceName, _mutexId);
+
+			IsLocked = true;
+			// check whether there's an local instance running already, but use local so this works in a multi-user environment
+			try
+			{
+				// Added Mutex Security, hopefully this prevents the UnauthorizedAccessException more gracefully
+				var sid = new SecurityIdentifier(WellKnownSidType.WorldSid, null);
+				var mutexsecurity = new MutexSecurity();
+				mutexsecurity.AddAccessRule(new MutexAccessRule(sid, MutexRights.FullControl, AccessControlType.Allow));
+				mutexsecurity.AddAccessRule(new MutexAccessRule(sid, MutexRights.ChangePermissions, AccessControlType.Deny));
+				mutexsecurity.AddAccessRule(new MutexAccessRule(sid, MutexRights.Delete, AccessControlType.Deny));
+
+				bool createdNew;
+				// 1) Create Mutex
+				_applicationMutex = new Mutex(true, _mutexId, out createdNew, mutexsecurity);
+				// 2) if the mutex wasn't created new get the right to it, this returns false if it's already locked
+				if (!createdNew && !_applicationMutex.WaitOne(100, false))
+				{
+					LOG.InfoFormat("{0} is already in use, mutex {1} is NOT locked for the caller", _resourceName, _mutexId);
+					IsLocked = false;
+					// Clean up
+					_applicationMutex.Close();
+					_applicationMutex = null;
+				}
+				else
+				{
+					if (createdNew)
+					{
+						LOG.InfoFormat("{0} has created & claimed the mutex {1}", _resourceName, _mutexId);
+					}
+					else
+					{
+						LOG.InfoFormat("{0} has claimed the mutex {1}", _resourceName, _mutexId);
+
+					}
+				}
+			}
+			catch (AbandonedMutexException e)
+			{
+				// Another instance didn't cleanup correctly!
+				// we can ignore the exception, it happend on the "waitone" but still the mutex belongs to us
+				LOG.WarnFormat("{0} didn't cleanup correctly, but we got the mutex {1}.", _resourceName, _mutexId);
+				LOG.Warn(e);
+			}
+			catch (UnauthorizedAccessException e)
+			{
+				LOG.ErrorFormat("{0} is most likely already running for a different user in the same session, can't create/get mutex {1} due to error.", _resourceName, _mutexId);
+				LOG.Error(e);
+				IsLocked = false;
+			}
+			catch (Exception ex)
+			{
+				LOG.ErrorFormat("Problem obtaining the Mutex {1} for {0}, assuming it was already taken!", _resourceName, _mutexId);
+				LOG.Error(ex);
+				IsLocked = false;
+			}
+			return IsLocked;
+		}
+
+		#region IDisposable Support
+		//  To detect redundant Dispose calls
+		private bool _disposedValue = false;
+
+		/// <summary>
+		/// The real disposing code
+		/// </summary>
+		/// <param name="disposing">true if dispose is called, false when the finalizer is called</param>
+		protected virtual void Dispose(bool disposing)
+		{
+			if (!_disposedValue)
+			{
+				if (_applicationMutex != null)
+				{
+					try
+					{
+						_applicationMutex.ReleaseMutex();
+						_applicationMutex = null;
+						LOG.InfoFormat("Released Mutex {0} for {1}", _mutexId, _resourceName);
+					}
+					catch (Exception ex)
+					{
+						LOG.ErrorFormat("Error releasing Mutex {0} for {1}", _mutexId, _resourceName);
+						LOG.Error(ex);
+					}
+
+				}
+				_disposedValue = true;
+			}
+		}
+
+		/// <summary>
+		/// Make sure the ApplicationMutex is disposed when the finalizer is called
+		/// </summary>
+		~ResourceMutex()
+		{
+			// Do not change this code. Put cleanup code in Dispose(bool disposing) above.
+			Dispose(false);
+		}
+
+		/// <summary>
+		/// The dispose interface, which calls Dispose(true) to signal that dispose is called.
+		/// </summary>
+		public void Dispose()
+		{
+			// Do not change this code. Put cleanup code in Dispose(bool disposing) above.
+			Dispose(true);
+			GC.SuppressFinalize(this);
+		}
+		#endregion
+	}
+}