Thread exit problem

Cedric Moonen

Hello, I have an application that has to start a new thread. In this thread I acquire and I calculate data. So, when I exit the program, I terminate the Thread but the thread doesn't exit! Here is the code: Starting the Thread:

CMyClass::Enable() //To start the Thread
{
//... do some stuff here
fEnabled = 1;
DWORD ThreadID;
m_hNewThread = CreateThread(
NULL, //No Security
0, //Same Stacksize
MyClassThreadProc, //Thread Proc
this, //Adress of my class
0, //start at once
&ThreadID);
}

Thread Proc function:

DWORD WINAPI MyClassThreadProc( LPVOID pParam )
{
CMyClass* pObject = (CMyClass*)pParam;

if (pObject == NULL)
	return -1;    // illegal parameter

// do something with 'pObject'
pObject->ServiceHandler();

return 0;    // thread completed successfully

}

Idle function:

void CMyClass::ServiceHandler()
{
while (fEnabled)
{
//Do stuf here: read and calculate data !
}
}

When I want to exit the Thread, I call this function:

void CMyClass::Disable()
{
if (!fEnabled)
return;

DWORD ExitCode;

fEnabled=0;

//Wait for ServiceThread 
GetExitCodeThread(m\_hNewThread,&ExitCode);
while(ExitCode == STILL\_ACTIVE)
	GetExitCodeThread(m\_hNewThread,&ExitCode);

//Close Serial Port
WRS232::Close();

return;

}

But that doesn't work !! The while loop in the Disable function never ends !!! I have not this problem when I set a breakpoint in this loop ! Thanks for help !!

Daniel Strigl

Have you added the volatile keyword to the fEnable flag? That's needed, otherwise the compiler will remove the while (fEnabled) statement during optimizing the code. Daniel ;) --------------------------- Never change a running system!

Cedric Moonen

Hello! Thanks for reply . I forgot the volatile keyword ! But, it doesn't work with it neither :(! When I exit my application, the Pocket PC goes much much more slowly (the thread is still in use)! Any idea?

Daniel Strigl

Take a look at the following code that I use in some of my projects. I create a thread at program start and terminate it when the user close the dialog.

BOOL CMyDlg::OnInitDialog()
{
CDialog::OnInitDialog();

// TODO: Add extra initialization here

m\_bRunning = TRUE;

// Create the thread and start it
m\_pSendDataThread = AfxBeginThread(SendData, this,                              
                         THREAD\_PRIORITY\_NORMAL,
                         0, // stack size
                         CREATE\_SUSPENDED);

ASSERT\_VALID(m\_pSendDataThread);
m\_pSendDataThread->m\_bAutoDelete = FALSE;
m\_pSendDataThread->ResumeThread(); // start the thread

return TRUE;  // return TRUE unless you set the focus to a control
              // EXCEPTION: OCX Property Pages should return FALSE

}

UINT CMyDlg::SendData(LPVOID pParam)
{
CMyDlg* pDialog = reinterpret_cast(pParam);
ASSERT(pDialog);

if (pDialog)
    pDialog->SendData(); // send the data to the server (host)

return 0;

}

void CMyDlg::SendData()
{
while (m_bRunning)
{
// do something
}
}

void CMyDlg::OnDestroy()
{
CDialog::OnDestroy();

// TODO: Add your message handler code here

m\_bRunning = FALSE;

// Wait until the thread is terminated
WaitForSingleObject(m\_pSendDataThread->m\_hThread, INFINITE);
delete m\_pSendDataThread;

}

Daniel ;) --------------------------- Never change a running system!

Cedric Moonen

Ok, that works fine with AfxBeginThread and WaitForSingleObject (I just replaced these functions). Don't know why it didn't work with my method! Thanks a lot for your help ;)