How can I get rid of an abandoned mutex?

Question

Summary:

Is there a way to clear out a mutex if the process that created it is dead and gone?

Answer 1

Don't know if this actually answers your question, but here's the code I use for this purpose:

  // Mutex object used to determine if there are multiple instances of this program running. 
  //  Note that this is a reference to a .Net Mutex object, not the Windows mutex itself.
  private static Mutex _onlyOneInstanceMutex;



  /// <summary>
  /// Method to test that there is not another instance of the program already running on this 
  /// machine, or at least in this Terminal Services session or Windows Vista / Windows 7 
  /// concurrent sessions session. If there is, a message box-style localized error message is 
  /// displayed and the value false is returned. This implies that this method should not be 
  /// used in programs that are run as a Windows service.
  /// 
  /// This implementation uses a .Net Mutex object in public storage to prevent it from being 
  /// garbage-collected. The name of the associated Windows mutex is simply the program name as 
  /// provided by the caller. Neither the .Net Mutex object nor the Windows mutex are ever 
  /// explicitly released; they remain in existence, perhaps in an "abandoned" state, until the 
  /// process that created them terminates.
  /// </summary>
  /// <returns>false if another instance running, otherwise true</returns>
  [SuppressMessage("Microsoft.Reliability", "CA2004:RemoveCallsToGCKeepAlive",
                   Justification = "Not sure if this is correct or not.")]
  public static bool TestOnlyOneInstance(string programName)
  {
     // Funny construct to prevent the Mutex from being garbage collected
     GC.KeepAlive(_onlyOneInstanceMutex);

     // Test if we are the first instance, and if so create the Windows mutex, making it 
     //  impossible for subsequent instances to successfully create their mutex
     bool firstInstance;
     _onlyOneInstanceMutex = new Mutex(false, programName, out firstInstance);
     if (firstInstance)
        return true;

     // Display a (possibly localized) error message, then return
     string errorMessage = MLocalizer.GetString("Error1", 
           "Another instance of this program is already running on this machine.") +
         "\n" + MLocalizer.GetString("Error2",
                                     "You cannot run two instances at the same time.") +
         "\n" + MLocalizer.GetString("Error3", "Please use the other instance.");
     MessageBox.Show(errorMessage, programName, MessageBoxButtons.OK, MessageBoxIcon.Error);
     return false;
  }

EDIT:

Only differences I can see in my code and yours is that I specify "initially owned" as false, and I have the funny thing about the garbage collection.

Oh, and I declare the Mutex static.