QThread stuck in second run - c++

Question

I have a QThread on my embedded device. every time I run the application my thread stuck after second run. I try to kill my thread after first run. Still device stuck after second run. I couldn't run my thread correctly.
Here is my code;
void ThreadCurrency::run()
{
QMutex mutex;
mutex.lock();
if(this->CurrencyStop == true)
{
mutex.unlock();
return;
}
QByteArray strdata;
// Create QProcess object
processCurrency = new QProcess();
processCurrency->start("curl --insecure -v --cacert /data/ca/cert.pem https://secure.*******************/fx.jsp");
if (processCurrency->waitForStarted(-1))
{
while(processCurrency->waitForReadyRead(-1))
{
strdata += processCurrency->readAllStandardOutput();
}
QMessageBox msgBox1;
msgBox1.setWindowTitle("eCode Read");
msgBox1.setText(strdata);
msgBox1.exec();
}
else
{
while(processCurrency->waitForReadyRead(-1))
{
strdata += processCurrency->readAllStandardError();
}
QMessageBox msgBox1;
msgBox1.setWindowTitle("eCode Error");
msgBox1.setText(strdata);
msgBox1.exec();
}
mutex.unlock();
sleep(1);
//*****************************************************************
emit CurrencyChanged(aGBP, aEUR, aUSD, sGBP, sEUR, sUSD);
}
** The Output shows in a json format:**
{
"date": "20171107", "currency": {
"dolar": {
"buy": "3,8200",
"sale": "3,9050",
"e_sale": "3,8200"
},
}
}
Thank you for suggestion. The QMutexLocker can’t work in my embedded device. QMutex and the QThread is the closes I can get in my device.
My problem is the below line: emit CurrencyChanged(aGBP, aEUR, aUSD, sGBP, sEUR, sUSD); The line runs but It doesn’t fire onCurrencyChanged SLOT. Anything in onCurrencyChanged doesn’t run. My main thread code is:
currencyThread = new ThreadCurrency (this);
connect(currencyThread,SIGNAL(CurrencyChanged(QString, QString, QString, QString, QString, QString)), this, SLOT(onCurrencyChanged (QString, QString, QString, QString, QString, QString)));
currencyThread->CurrencyStop = false;
currencyTimer = new QTimer(this);
connect(currencyTimer, SIGNAL(timeout()),this, SLOT(showCurrencyStatus()));
currencyTimer->start(30000);
void MainWindow::onCurrencyChanged(QString aGBP, QString aEUR, QString aUSD, QString sGBP, QString sEUR, QString sUSD)
{
// SHOW Currency
ui->lblALIS_STG->setText(aGBP);
ui->lblALIS_EUR->setText(aEUR);
ui->lblALIS_USD->setText(aUSD);
QCoreApplication::processEvents();
}

Answer 1

1) You are not allowed to access Widgets in a thread besides the main thread.
Thus move all QMessageBox code to the main thread (e.g. after receiving the CurrencyChanged signal).
2) Make sure, that the CurrencyChanged signal is connected using a QueuedConnection, otherwise, your GUI will be executed inside the secondary worker thread.
3) Do not use QMutex directly, use a QMutexLocker instead
4) Why do you need the Mutex anyhow? Locking based on (arbitrary) input thus arbitrary time is close to deadlocking your application.