Slot priority in multithread

**maratk1n** · 11th May 2017, 16:42

Hi all!

Small fragment of the project:

mainwindow.cpp

Qt Code:

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//constructor
    QThread *thread = new QThread;         
    //thread = new QThread(this);             
    valve = new Valve(7);                   
    pressureSensors = new PressureSensors;  
    valve->moveToThread(thread);
    pressureSensors->moveToThread(thread);
    connect(pressureSensors, SIGNAL(remoteSignal(bool)), this, SLOT(readPressureSensors(bool)));
    connect(valve, SIGNAL(remoteSignal(bool)), this, SLOT(updateStates(bool)));
    connect(this, SIGNAL(valveOpen(int)), valve, SLOT(open(int)));
    connect(this, SIGNAL(valveClose(int)), valve, SLOT(close(int)));
    connect(valve, SIGNAL(valveStatus(int,bool,bool)), this, SLOT(valveIndicate(int,bool,bool)));
    QTimer *sensorsReadTimer = new QTimer(this);    
    sensorsReadTimer->moveToThread(thread);
    connect(sensorsReadTimer, SIGNAL(timeout()), pressureSensors, SLOT(readSensors()));
    sensorsReadTimer->start(100);                   
    QTimer *valvesReadTimer = new QTimer(this);     
    valvesReadTimer->moveToThread(thread);
    connect(valvesReadTimer, SIGNAL(timeout()), valve, SLOT(getAllStates()));
    valvesReadTimer->start(100);                   
    thread->start();
//***//
void MainWindow::openValve(int id)
{
    valveButton[id]->setEnabled(false);
    //valve->open(id);
    emit valveOpen(id);
}

//constructor
    QThread *thread = new QThread;         
    //thread = new QThread(this);             
    valve = new Valve(7);                   
    pressureSensors = new PressureSensors;  
    valve->moveToThread(thread);
    pressureSensors->moveToThread(thread);
    connect(pressureSensors, SIGNAL(remoteSignal(bool)), this, SLOT(readPressureSensors(bool)));
    connect(valve, SIGNAL(remoteSignal(bool)), this, SLOT(updateStates(bool)));
    connect(this, SIGNAL(valveOpen(int)), valve, SLOT(open(int)));
    connect(this, SIGNAL(valveClose(int)), valve, SLOT(close(int)));
    connect(valve, SIGNAL(valveStatus(int,bool,bool)), this, SLOT(valveIndicate(int,bool,bool)));
    QTimer *sensorsReadTimer = new QTimer(this);    
    sensorsReadTimer->moveToThread(thread);
    connect(sensorsReadTimer, SIGNAL(timeout()), pressureSensors, SLOT(readSensors()));
    sensorsReadTimer->start(100);                   
    QTimer *valvesReadTimer = new QTimer(this);     
    valvesReadTimer->moveToThread(thread);
    connect(valvesReadTimer, SIGNAL(timeout()), valve, SLOT(getAllStates()));
    valvesReadTimer->start(100);                   
    thread->start();
//***//
void MainWindow::openValve(int id)
{
    valveButton[id]->setEnabled(false);
    //valve->open(id);
    emit valveOpen(id);
}

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protocol.cpp

Qt Code:

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bool Valve::open(int id)
{
    QByteArray arr;
    arr.resize(7);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x02;
    arr[3] = 0x02;
    arr[4] = id + 1;
    arr[5] = 0xFF;
    arr[6] = 0x00 - arr[1] - arr[2] - arr[3] - arr[4] - arr[5];
 
    QByteArray response = ComPort::get().requestResponse(arr);
    if(response[0] == arr[0])
    {
        qDebug() << "ÐºÐ»Ð°Ð¿Ð°Ð½ â„–: " << id << " Ð¾Ñ‚ÐºÑ€Ñ‹Ñ‚!";
        valveState[id] = true;
        emit valveStatus(id, 1, 1);
        return 1;
    }
    emit valveStatus(id, 1, 0);
    return 0;
}
bool Valve::getAllStates()
{
    QByteArray arr;
    arr.resize(5);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x00;
    arr[3] = 0x00;
    arr[4] = 0x00 - arr[1] - arr[2] - arr[3];
 
    QByteArray response = ComPort::get().requestResponse(arr);
    if(response[0] == arr[0])
    {
        QBitArray bitStates(16);   
 
        for (int i = 4; i<6; i++)   
            for (int b = 0; b<8; b++)
                bitStates.setBit((i-4)*8+b, response.at(i)&(1<<b));
        for (int i = 0; i < valveState.size(); i++)         
            valveState[i] = bitStates[i];
        for (uint i = 0; i < sizeof(fittingState); i++) 
            fittingState[i] = bitStates[i+8];
        emit remoteSignal(1);
        return 1;
    }
    emit remoteSignal(0);
    return 0;
}
//***//
QByteArray ComPort::requestResponse(const QByteArray &data)
{
    mutex->lock();
    QByteArray readBuf;
    qDebug() << "-------------------------";
    if(!serial->isOpen())
        open();
    int attempts = 1;
    while (attempts <= REQATTEMPTS) {      //3 Ð¿Ð¾Ð¿Ñ‹Ñ‚ÐºÐ¸
        if (serial->isWritable())
        {
            serial->write(data);
            qDebug() << "ÐŸÐ¾Ð¿Ñ‹Ñ‚ÐºÐ° â„– " << attempts;
            qDebug() << "Ð—Ð°Ð¿Ñ€Ð¾Ñ: " << data.toHex();
            while (serial->waitForReadyRead(WAITFORREADY)) {
                readBuf += serial->readAll();
                if (crcCheck(readBuf) && data[2] == readBuf[2] ){  //ÐµÑÐ»Ð¸ CRC Ð¸ ÐºÐ¾Ð¼Ð°Ð½Ð´Ð° ÑÐ¾ÑˆÐ»Ð¸ÑÑŒ -- ÑƒÑÐ¿ÐµÑ…!
                    qDebug() << "ÐžÑ‚Ð²ÐµÑ‚: " << readBuf.toHex();
 
                    responseCount++;
                    qDebug() << "ÐšÐ¾Ð»-Ð²Ð¾ Ð·Ð°Ð¿Ñ€Ð¾ÑÐ¾Ð²:  " << responseCount;
                    qDebug() << "ÐšÐ¾Ð»-Ð²Ð¾ Ñ‚Ð°Ð¹Ð¼Ð°ÑƒÑ‚Ð¾Ð²: " << timeoutCount;
                    float percent = timeoutCount * 100;
                    percent = percent / responseCount;
                    qDebug() << "ÐŸÑ€Ð¾Ñ†ÐµÐ½Ñ‚ ÐºÐ¾ÑÑÐºÐ¾Ð²:  " << QString::number(percent, 'f', 3) << "%";
 
                    close();
                    mutex->unlock();
                    return readBuf;
                }
            }
            //qDebug() << readBuf.toHex();
            readBuf.clear();
            qDebug() << "Ð¢Ð°Ð¹Ð¼Ð°ÑƒÑ‚...";
 
            timeoutCount++;
 
            close();
            open();
            attempts++;
        }
        else
        {
            qDebug() << "ÐŸÐ¾Ñ€Ñ‚ " << portName << " Ð½Ðµ Ð¿Ð¸ÑˆÐµÑ‚ÑÑ!";
            close();
            mutex->unlock();
            return 0;
        }
 
    }
    close();
    mutex->unlock();
    return 0;
}

bool Valve::open(int id)
{
    QByteArray arr;
    arr.resize(7);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x02;
    arr[3] = 0x02;
    arr[4] = id + 1;
    arr[5] = 0xFF;
    arr[6] = 0x00 - arr[1] - arr[2] - arr[3] - arr[4] - arr[5];

    QByteArray response = ComPort::get().requestResponse(arr);
    if(response[0] == arr[0])
    {
        qDebug() << "ÐºÐ»Ð°Ð¿Ð°Ð½ â„–: " << id << " Ð¾Ñ‚ÐºÑ€Ñ‹Ñ‚!";
        valveState[id] = true;
        emit valveStatus(id, 1, 1);
        return 1;
    }
    emit valveStatus(id, 1, 0);
    return 0;
}
bool Valve::getAllStates()
{
    QByteArray arr;
    arr.resize(5);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x00;
    arr[3] = 0x00;
    arr[4] = 0x00 - arr[1] - arr[2] - arr[3];

    QByteArray response = ComPort::get().requestResponse(arr);
    if(response[0] == arr[0])
    {
        QBitArray bitStates(16);   

        for (int i = 4; i<6; i++)   
            for (int b = 0; b<8; b++)
                bitStates.setBit((i-4)*8+b, response.at(i)&(1<<b));
        for (int i = 0; i < valveState.size(); i++)         
            valveState[i] = bitStates[i];
        for (uint i = 0; i < sizeof(fittingState); i++) 
            fittingState[i] = bitStates[i+8];
        emit remoteSignal(1);
        return 1;
    }
    emit remoteSignal(0);
    return 0;
}
//***//
QByteArray ComPort::requestResponse(const QByteArray &data)
{
    mutex->lock();
    QByteArray readBuf;
    qDebug() << "-------------------------";
    if(!serial->isOpen())
        open();
    int attempts = 1;
    while (attempts <= REQATTEMPTS) {      //3 Ð¿Ð¾Ð¿Ñ‹Ñ‚ÐºÐ¸
        if (serial->isWritable())
        {
            serial->write(data);
            qDebug() << "ÐŸÐ¾Ð¿Ñ‹Ñ‚ÐºÐ° â„– " << attempts;
            qDebug() << "Ð—Ð°Ð¿Ñ€Ð¾Ñ: " << data.toHex();
            while (serial->waitForReadyRead(WAITFORREADY)) {
                readBuf += serial->readAll();
                if (crcCheck(readBuf) && data[2] == readBuf[2] ){  //ÐµÑÐ»Ð¸ CRC Ð¸ ÐºÐ¾Ð¼Ð°Ð½Ð´Ð° ÑÐ¾ÑˆÐ»Ð¸ÑÑŒ -- ÑƒÑÐ¿ÐµÑ…!
                    qDebug() << "ÐžÑ‚Ð²ÐµÑ‚: " << readBuf.toHex();

                    responseCount++;
                    qDebug() << "ÐšÐ¾Ð»-Ð²Ð¾ Ð·Ð°Ð¿Ñ€Ð¾ÑÐ¾Ð²:  " << responseCount;
                    qDebug() << "ÐšÐ¾Ð»-Ð²Ð¾ Ñ‚Ð°Ð¹Ð¼Ð°ÑƒÑ‚Ð¾Ð²: " << timeoutCount;
                    float percent = timeoutCount * 100;
                    percent = percent / responseCount;
                    qDebug() << "ÐŸÑ€Ð¾Ñ†ÐµÐ½Ñ‚ ÐºÐ¾ÑÑÐºÐ¾Ð²:  " << QString::number(percent, 'f', 3) << "%";

                    close();
                    mutex->unlock();
                    return readBuf;
                }
            }
            //qDebug() << readBuf.toHex();
            readBuf.clear();
            qDebug() << "Ð¢Ð°Ð¹Ð¼Ð°ÑƒÑ‚...";

            timeoutCount++;

            close();
            open();
            attempts++;
        }
        else
        {
            qDebug() << "ÐŸÐ¾Ñ€Ñ‚ " << portName << " Ð½Ðµ Ð¿Ð¸ÑˆÐµÑ‚ÑÑ!";
            close();
            mutex->unlock();
            return 0;
        }

    }
    close();
    mutex->unlock();
    return 0;
}

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If I do not put valve and pressureSensors in a separate thread, then everything works more or less normally.
But if I put them in a separate thread, the valve opening slot works very late (~ 10 seconds, as lucky). As I understand it, this is because the signal is emitted from the main thread, and the slot is in the other thread. Is it possible to build a queue?

Slot open from Valve class must have the highest priority.

Thankful in advance for the help!

**Santosh Reddy** · 12th May 2017, 11:07

There are 2 problems in the code
1. QTimers are created with a parent. Objects with a parent cannot be moved to a thread
Fix: Create QTimer without parent

2. QTimer is started after moving to thread. You cannot and should not start a timer which is in another thread.
Fix: Start the timer before moving to the thread.

Qt Code:

Switch view

...
    QTimer *sensorsReadTimer = new QTimer(this);    // <<<<<<<<<< Change to new QTimer();
    sensorsReadTimer->moveToThread(thread);
    connect(sensorsReadTimer, SIGNAL(timeout()), pressureSensors, SLOT(readSensors()));
    sensorsReadTimer->start(100);    // <<<<<<<<<< Start the timer before moving to the thread                   
    QTimer *valvesReadTimer = new QTimer(this);     // <<<<<<<<<< Change to new QTimer();    
    valvesReadTimer->moveToThread(thread);
    connect(valvesReadTimer, SIGNAL(timeout()), valve, SLOT(getAllStates()));
    valvesReadTimer->start(100);    // <<<<<<<<<< Start the timer before moving to the thread                   
    ...

...
    QTimer *sensorsReadTimer = new QTimer(this);    // <<<<<<<<<< Change to new QTimer();
    sensorsReadTimer->moveToThread(thread);
    connect(sensorsReadTimer, SIGNAL(timeout()), pressureSensors, SLOT(readSensors()));
    sensorsReadTimer->start(100);    // <<<<<<<<<< Start the timer before moving to the thread                   
    QTimer *valvesReadTimer = new QTimer(this);     // <<<<<<<<<< Change to new QTimer();    
    valvesReadTimer->moveToThread(thread);
    connect(valvesReadTimer, SIGNAL(timeout()), valve, SLOT(getAllStates()));
    valvesReadTimer->start(100);    // <<<<<<<<<< Start the timer before moving to the thread                   
    ...

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**maratk1n** · 12th May 2017, 12:04

Originally Posted by Santosh Reddy

There are 2 problems in the code
1. QTimers are created with a parent. Objects with a parent cannot be moved to a thread
Fix: Create QTimer without parent

2. QTimer is started after moving to thread. You cannot and should not start a timer which is in another thread.
Fix: Start the timer before moving to the thread.

Thank you very much!

This, it seems, helped to solve the problem.