I am creating a multithreade application to read from multiple serial devices at a time and send data to a network. My application works but I am not sure about how to perfectly use mutex in my application.
My application crashes sometimes, So I used QMutex to solve the issue.

My code is given

I created a static mutex object

Qt Code: 
  1. class MyApp : public QObject
  2. {
  3.     Q_OBJECT
  4.  
  5. public:
  6.     explicit MyApp(QObject *parent = 0);
  7.     ~MyApp();
  8.  
  9.     static int s_iCount;
  10.     static QList<QString> s_resultList;
  11.  
  12.     static bool s_bStopThreadFlag;
  13.  
  14.     static QMutex m_mutex;
  15.     SerialDevice *objDevice;
  16.     QThreadEx *objDeviceThread;
  17.  
  18.     void removeDeviceConnction();
  19.     void startDeviceReading();
  20.  
  21.  
  22.  
  23.  signals:
  24.    void exitThread();
  25.    void sendInstructionToDevice(QString  strInstructions);
  26.  
  27. private:
  28.  
  29.     QString m_strResultFull;
  30.  
  31.  
  32. };
  33.  
  34.  
  35. MyApp::MyApp(QObject *parent) :
  36.     QObject(parent),
  37.     m_iDeviceReadingInterval(1000)
  38.     {
  39.  
  40.      // m_mutex.lock();
  41.         s_iCount = 0;
  42.         s_bStopThreadFlag = false;
  43.         // m_mutex.unlock();
  44.       startDeviceReading();
  45.         // timerSendDataDelay->start();
  46. }
  47.  
  48.  
  49. void MyApp::startDeviceReading()
  50. {
  51.  
  52.  
  53.        QList<QextPortInfo>  portlist =  portinfo.getPorts();
  54.  
  55.        for(int iCount = 0; iCount < portlist.count(); iCount++)
  56.        {
  57.  
  58.  
  59.             objDeviceThread= new QThreadEx();
  60.             objDevice = new SerialDevice(portlist[iCount].portName, 0);
  61.             objDevice->setReadingInterval(m_iDeviceReadingInterval);
  62.  
  63.             connect(this, SIGNAL(exitThread()), objDevice, SLOT(finishWork()));
  64.             connect(this, SIGNAL(setReadingInterval(int)), objDevice, SLOT(setReadingInterval(int)));
  65.             connect(this, SIGNAL(sendInstructionToDevice(QString)), objDevice, SLOT(sendInstructionToDevice(QString)));
  66.             connect(this, SIGNAL(startReadingTimer()), objDevice, SLOT(startReadingTimer()));
  67.  
  68.  
  69.             objDevice->m_strPortName = portlist[iCount].portName;
  70.             objDevice->connect(objDeviceThread,
  71.                   SIGNAL(started()),
  72.                   SLOT(produce()));
  73.  
  74.             objDevice->moveToThread(objDeviceThread);
  75.             objDeviceThread->start();
  76.          }
  77. }
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Created the thred object and started the thred


And in my serial device class accesses the static variables and static mutex like this

Qt Code: 
  1. void SerialDevice::produce()
  2. {
  3.  
  4.  
  5.         // MyApp::m_mutex.lock();
  6.         MyApp::s_iCount++;
  7.         m_iThredCount =  MyApp::s_iCount;
  8.         MyApp::s_resultList.append("null");
  9.         MyApp::s_ValueList.append("null");
  10.         //MyApp::m_mutex.unlock();
  11.  
  12.         PortSettings settings = {BAUD19200, DATA_8, PAR_NONE, STOP_1, FLOW_OFF, 10};
  13.         m_port = new QextSerialPort(m_strPortName, settings, QextSerialPort::EventDriven);
  14.  
  15.         timer = new QTimer(this);
  16.         timer->setInterval(20);
  17.  
  18.         m_pagevalue = new char[20];
  19.  
  20.          connect(timer, SIGNAL(timeout()), SLOT(onReadyRead()));
  21.          connect(m_port, SIGNAL(readyRead()), SLOT(onReadyRead()));
  22.  
  23.         if (!m_port->isOpen())
  24.         {
  25.            m_port->setPortName(m_strPortName);
  26.             m_port->open(QIODevice::ReadWrite);
  27.         }
  28.  
  29.  
  30.         if (m_port->isOpen() && m_port->queryMode() == QextSerialPort::Polling)
  31.            timer->start();
  32.         else
  33.             timer->stop();
  34. }
  35.  
  36. void SerialDevice::onReadyRead()
  37. {
  38.  m_strData = "";
  39.     if (m_port->bytesAvailable())
  40.     {
  41.  
  42.         m_strData = m_port->readAll();
  43.  
  44.  
  45.        //  MyApp::m_mutex.lock();
  46.         MyApp::s_ValueList.replace(m_iThredCount - 1, strReadings);
  47.        //  MyApp::m_mutex.unlock();
  48.  
  49.     }
  50. }
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