Object Synchronization method was called from unsynchronized block while using Mutex - windows-runtime

Question

I am Trying to create a Windows Universal App with a Background Task.
I am trying to Write a Background task that Triggers Upon an Incoming bluetooth connection.
To prevent both the foreground and background from creating a connection. I am trying to implement the Same Mutex in Both the Foreground and Background.
When I read the Data from the Bluetooth Device I am getting the Following Error.
Object Synchronization method was called from unsynchronized block
To my Surprise this Error comes Occasionally . Am I missing Something ?
Here's My Code :
public sealed class RFBackgroundTask : IBackgroundTask
{
.... Variable declarations
public async void Run(IBackgroundTaskInstance taskInstance)
{
BackgroundTaskDeferral deferral = taskInstance.GetDeferral();
try
{
taskInstance.Canceled += new BackgroundTaskCanceledEventHandler(OnCanceled);
Debug.WriteLine("RFComm Task Running");
hotwatchConnection = taskInstance.TriggerDetails as RfcommConnectionTriggerDetails;
socket = hotwatchConnection.Socket;
reader = new DataReader(socket.InputStream);
// n = new Notification(hotwatchConnection.RemoteDevice.HostName);
await Read();
}
catch (System.Exception e)
{
Debug.WriteLine("RFComm Task Error: {0}", e.Message);
if (ismutexReleased == false)
{
Debug.WriteLine("Releaseing mutex because of error {0}:", e.Message);
connectionMutex.ReleaseMutex();
ismutexReleased = true;
}
}
finally
{
if (ismutexReleased == false)
{
Debug.WriteLine("Releasing Mutex 2");
connectionMutex.ReleaseMutex();
}
ismutexReleased = true;
}
deferral.Complete();
}
public IAsyncAction Read()
{
return Task.Run(async () =>
{
try
{
connectionMutex = new Mutex(false, CONNECTION_MUTEX_NAME);
// Attempt to wait for the mutex
var waitResult = connectionMutex.WaitOne();
if (waitResult)
{
Debug.WriteLine("Aquired Mutex Successfully");
}
// If the wait was not successful, fail the connect operation
if (!waitResult) { throw new TimeoutException(); }
if (reader != null)
{
uint length = 500;
reader.InputStreamOptions = InputStreamOptions.Partial;
uint len = await reader.LoadAsync(length);
String message = reader.ReadString(len);
Debug.WriteLine("Read " + message + " In the First Attemnpt");
var roamingSettings = Windows.Storage.ApplicationData.Current.RoamingSettings;
roamingSettings.Values["COMMAND"] = message;
//if(!message.StartsWith("01"))
//{
// await ProcessCommand(message);
//}
}
reader.Dispose();
socket.Dispose();
socket = null;
if (waitResult == true)
connectionMutex.ReleaseMutex();
ismutexReleased = true;
Debug.WriteLine("Released Mutex successfully after reading data");
}
catch (Exception e)
{
Debug.WriteLine(e.Message);
if (ismutexReleased == false)
{
Debug.WriteLine("Releaseing mutex because of error {0}:", e.Message);
connectionMutex.ReleaseMutex();
ismutexReleased = true;
}
throw;
}
finally
{
if (ismutexReleased == false)
{
connectionMutex.ReleaseMutex();
Debug.WriteLine("Releasing Mutex");
}
ismutexReleased = true;
}
}).AsAsyncAction();
}
}

Answer 1

The Mutex must be released on the same thread that it was acquired.
When you await an async method you are returned to the same context, you are not guaranteed to be returned to the same thread.
Use a Semaphore instead.